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Matter In Our Surroundings Multiple Choice Questions

Question 1. A diver can cut through water in a swimming pool. The property shown by the matter is

1. The particles are of very small size
2. The matter has space between them
3. The particles are in a solid state
4. The particles are running here and there, and have no space between them

Answer: 2. The matter has space between them

A diver can cut through water because water is a liquid and has space between the water molecules due to the weak force of attraction among the water molecules.

Question 2. Crystals of KMnO₄ in water prove that

1. KMnO₄ is of red color
2. KMnO₄ is acidic
3. KMnO₄ is made up of millions of tiny particles
4. KMnO₄ is a reducing agent

Answer: 3. KMnO₄ is made up of millions of tiny particles

When crystals of KMnO₄ are added to water, it dissociates into millions of tiny particles, which proves that KMn04 is made up of millions of tiny particles.

Question 3. Honey dissolves slowly in water as a solvent, because

1. It has a high boiling point
2. It vaporises easily
3. It is highly viscous
4. It has a low melting point

Answer: 3. It is highly viscous

When honey is dissolved in water as a solvent. It dissolves slowly because of its highly viscous nature, i.e. It has high density and a strong force of attraction between the honey molecules.

Question 4. Gases show a faster rate of diffusion because

1. Of higher boiling point
2. Of low intermolecular space
3. Of high melting point
4. Of large intermolecular space

Answer: 4. Of large intermolecular space

Gases show a faster rate of diffusion because they have weak intermolecular forces between them and move at higher speeds. As a result, these have large intermolecular space between the molecules.

Question 5. Which of the following is found in a solid state at room temperature?

1. Stone
2. Sand
3. Mercury
4. Both (1) and (2)

Answer: 4. Both (1) and (2)

• Stone and sand are found in a solid state at room temperature because of a strong attractive force among their particles, (i.e. the particles of stone and sand are held together with strong attractive forces).
• Thus, the intermolecular space among them is very small and these exist as solids, mercury is the only metal which is found in a liquid state at room temperature.

Question 6. The similarity between a liquid and a gas is

1. Both do not show a definite shape
2. Both have a definite volume
3. Both have the same b.p
4. Both have the same nature

Answer: 1. Both do not show a definite shape

• Liquids and gases both are considered fluids but due to weak intermolecular force of attraction, gases occupy the shape and volume of a container.
• Liquids have slightly more force of attraction and thus have definite volume but not definite shape.
• Hence, we can say that gases have no definite volume and shape, (as they occupy the whole volume and shape of a container) but liquids have definite volume but no definite shape (i.e. they occupy the shape of a container.)

Question 7. For a given mass, identify the correct order of density.

1. Water < chalk < cotton <air
2. Chalk < water < cotton < air
3. Air < cotton < water < chalk
4. Cotton < air < water < chalk

Answer: 3 and 4

Mass (m) per unit volume (V) is called density

i.e. \(d=\frac{m}{V}\). As intermolecular space (i.e. volume) among the molecules of the given particles is as follows

chalk < water < cotton < air.

Therefore, the order of density will be,

air < cotton < water < chalk

∴ \(\left[d \propto \frac{1}{V}\right]\)

Hence,(3) is the correct option.

Question 8. A gas fills the vessel in which it is kept, because

1. Of weak intermolecular attractive forces
2. Of strong intermolecular attractive forces
3. Of very weak intermolecular repulsive forces
4. Of fluidity

Answer: 1. Of weak intermolecular attractive forces

A gas fills the vessel in which it is kept because of weak intermolecular attractive forces among the gas molecules. As a result, they can move in the entire vessel and occupy the whole volume of the vessel in which they are kept.

Question 9. A gas can exists the pressure on the walls of the container because

1. Of high molecular mass
2. Of high kinetic energy
3. Of high repulsive forces
4. Of low intermolecular space

Answer: 2.  Of high kinetic energy

Due to the high kinetic energy (K.E.) possessed by the gas particles, they move with high speed and put pressure on the walls of the container.

Question 10. Any substance is said to be a solid because

1. Of definite volume and shape
2. Of high rate of diffusion
3. Of fluidity
4. Of the weak force of attraction

Answer: 1. Of definite volume and shape

A substance is said to be a solid because of its definite volume and shape. Since the particles of solids are rigid and have a strong force of attraction, they offer a definite volume and shape to the solids.

Question 11. A solid substance possess

1. Rigidity fluidity and weak force of attraction
2. Rigidity fluidity and fixed volume
3. Rigidity fixed volume and high attractive forces of attraction
4. Rigidity fixed shape and large intermolecular space between particles

Answer: 3. Rigidity fixed volume and high attractive forces of attraction

• The solids are rigid and have fixed volume due to the strong force of attraction.
• They can not flow and, therefore are not considered as fluid. Due to strong forces of attraction, the intermolecular space between their particles is very small.

Question 12. Add a teaspoon full of table salt to water and stir it for some time. On standing, we find that

1. Water level rises
2. The water level remains as such
3. Water level decreases
4. Water starts boiling

Answer: 2. Water level remains as such

The water level remains as such because table salt dissolves in water completely and occupies the spaces between the particles of water.

Question 13. The same quantity of air and water are compressed with the same pressure, the correct conclusion we find is

1. Air is compressed more than the water
2. Water is compressed more than the air
3. Both are compressed to the same extent
4. No compression is found in the cases

Answer: 1. Air is compressed more than the water

• Air will compressed more than water due to the very weak force of attraction among the air molecules as compared to water. As a result, the intermolecular space in air is more than that of water.
• Hence on applying the same amount of pressure, the air will compressed more than the water.

Question 14. Temperature 200° C equals nearly to

1. 300 K
2. 373 K
3. 473 K
4. -73 K

Answer: 3.

Celsius scale (° C) and Kelvin scale are related as follows.

Temperature on Kelvin scale

= Temperature on ° C + 273.

Hence, temperature on Kelvin scale = 200 + 273 = 473 K

∴ The option is the correct answer.

Question 15. According to the Kelvin scale, 0° C is equal to

1. 0 K
2. 100 K
3. 273 K
4. – 273 K

Answer: 3. 273 K

Question 16. A large volume of compressed natural gas (CNG) is available in small cylinders due to its property of

1. Low density
2. High compressibility
3. Easy availability
4. High inflammability

Answer: 2. High compressibility

Question 17. Which of the following has the highest kinetic energy?

1. Particles of water at 100° C
2. Particles of steam at 100° C
3. Particles of ice at 0° C
4. Particles of water at 0° C

Answer: 2. Particles of steam at 100° C

Question 18. The density of a substance is defined as

1. Product of mass and volume
2. Ratio of mass and volume
3. Product of mass and temperature
4. Ratio of mass and temperature

Answer: 2. Ratio of mass and volume

Question 19. The process involving the change of state from solid to gas state is known as

1. Melting
2. Sublimation
3. Fusion
4. Vapourisation

Answer: 2. Sublimation

Question 20. The temperature at which the solid melts to become a liquid at the atmospheric pressure is known as

1. Melting point
2. Boiling point
3. Freezing point
4. None of these

Answer: 1. Melting point

Question 21. Which of the following is accompanied by cooling?

1. Vaporisation
2. Evaporation
3. Condensation
4. Sublimation

Answer: 2. Evaporation

Question 22. Which of the following does not affect the rate of evaporation?

1. Surface area
2. Insoluble heavy impurities
3. Temperature
4. All of these

Answer: 2. Insoluble heavy impurities

Matter in Our Surroundings Fill In The Blanks.

Question 1. Evaporation of a liquid at room temperature leads to a ____ effect.
Answer:  Cooling

Question 2. At room temperature, the forces of attraction between the particles of solid substances are ____ than those that exist in the gaseous state.
Answer: Stronger

Question 3. The arrangement of particles is less ordered in the state. However, there is no order in the ____ state.
Answer: liquid; gaseous

Question 4. ____ is the change of gaseous state directly to solid state without going through the state.
Answer: Sublimation; liquid

Question 5. The phenomenon of change of a liquid into the gaseous state at any temperature below its boiling point is called ____
Answer: Evaporation

 Class 9 Science Chapter 2 Is Matter Around Us Pure Long Answer Type Questions

Question 1.

1. What are elements?
2. What are the three main types of elements?
3. Write a property of each type of element.

Answer:

1. An element consists of only one type of atom. It is a basic form of matter that cannot be broken down into simpler substances by chemical reactions.
2. Metals, non-metals and metalloids.
3. Metals—Malleable and ductile Non-metals—Brittle Metalloids—Semiconductors

Question 2.

1. Distinguish among the true solution, suspension and colloid in a tabular form under the following heads:
   1. Stability
   2. Filterability
   3. Type of mixture
2. Give expression for the concentration of a solution. How will you prepare a 10% solution of glucose by mass in water?

Answer:

Distinctions between true solution, suspension and colloid are:

The methods by which the concentration of a solution can be expressed are:

Mass by mass% of solution

⇒ \(=\frac{\text { Mass of solute }}{\text { Mass of solution }} \times 100\)

Mass by volume% of solution

⇒ \(\frac{\text { Mass of solute }}{\text { Mass of solution }} \times 100\)

A 10 per cent solution of glucose can be prepared by dissolving 10 g of glucose in 90 g of water.

Read and Learn More Class 9 Science Solutions

Question 3. Write your observations when the following processes take place:

1. An aqueous solution of sugar is heated to dryness.
2. A saturated solution of potassium chloride prepared at 608°C is allowed to cool at room temperature.
3. A mixture of iron filings and sulphur powder is heated strongly.
4. A beam of light is passed through a colloidal solution.
5. Dilute HCl is added to the mixture of iron and sulphur.

Answer:

1. Sugar remains as a residue in the form of a solid mass.
2. Potassium chloride crystallises out.
3. A black-coloured compound is formed.
4. The path of the light becomes visible.
5. A colourless gas has evolved.

Question 4.

1. Pond water contains sand grains, clay particles, salt, pieces of paper and some air bubbles. Select from amongst these, an example each of a solvent, solute, colloid and suspension.
2. Give one example of each of the following:
3. A solution of gas in liquid
4. A solution of two solids
5. A solution of two gases

Answer:

1. Solvent-Water  Solute-Salt, pieces of paper, air bubbles Colloid-Mixture of air bubbles and water Suspension-
   1. A mixture of water and sand grains
   2. A mixture of water and clay particles
2. Aerated drinks,
   1. Brass,
   2. Air

Question 5. Classify each of the following as a physical or a chemical change. Give reasons.

1. Drying of a shirt in the sun.
2. Rising of hot air over a radiator.
3. Burning of kerosene in a lantern.
4. Change the colour of black tea by adding lemon juice to it.
5. Churning of milk cream to get butter.

Answer:

1. Physical change Because the evaporation of water takes place, but no change occurs in the composition of the substance.
2. Physical change It involves ing only the movement of with it, no change in the composition of air.
3. Physical as well as chemical change Physical change occurs when kerosene vapourises. After that, the burning of kerosene is a chemical change because, during burning, kerosene oil gets converted into carbon dioxide and water both of which are new compounds.
4. Chemical change The acid present in lemon juice will react with the constituent (for example., caffeine) present in black tea.
5. Physical change As there is no change in composition. Only the separation of components takes place by the physical phenomenon of centrifugation. However, butter will not change to milk easily.

Question 6. Iron filings and sulphur were mixed and divided into two parts, A and B. Part A was heated strongly while part B was not heated. Dilute hydrochloric acid was added to both the parts and the evolution of gas was seen in both cases. How will you identify the gases that evolved?
Answer:

⇒ \(\underbrace{\mathrm{Fe}+\mathrm{S}}_{\text {Part } A} \stackrel{\Delta}{\longrightarrow} \mathrm{FeS}\)

Part B is not heated, so the reaction will be as such

⇒ \(\underset{\text { (In Part B) }}{\mathrm{Fe}}+2 \mathrm{HCl} \text { (dil.) } \longrightarrow \mathrm{FeCl}_2+\mathrm{H}_2 \uparrow\)

In part A, H₂S gas is produced, which is identified by its characteristic smell of rotten eggs. In part B, H₂ gas is produced.

Hydrogen gas is tested by bringing a burning matchstick near the mouth of the test tube. It burns with a pop sound and water is formed.

Question 7. Rama tested the solubility of four substances at different temperatures and found a gram of each substance dissolved in 100 g of water to form a saturated solution.

1. Which solution is least soluble at 293 K?
2. Which substance shows a maximum change in its solubility when the temperature is raised from 293 K to 313 K?
3. Find the amount of ammonium chloride that will separate when 55 g of its solution at 333 K is cooled to 293 K.
4. What is the effect of temperature on the solubility of a salt?
5. What mass of sodium chloride would be needed to make a saturated solution in 10 g of water at 293 K?

Answer:

1. Potassium nitrate.
2. Potassium nitrate.
3. At 333 K, ammonium chloride dissolved per 100 g = 55g.
   1. At 293 K, ammonium chloride dissolved per 100 g = 37g
   2. When a solution is cooled from 333 K to 293 K, the amount of ammonium chloride that will separate =55 -37= 18g
4. The solubility of a salt (sold) increases with the rise in temperature and vice-versa.
5. At 293K, the amount of NaCl dissolved in 100 g of water = 36 g,

∴ At 293 K, the amount of NaCl dissolved in 10 g water = \(\frac{36}{100} \times 10=3.6 \mathrm{~g}\)

Question 8. During an experiment, the students were asked to prepare a 10% (mass/mass) solution of sugar in water. Ramesh dissolved 10 g of sugar in 100 g of water while Sarika prepared it by dissolving 10 g of sugar in water to make 100 g of the solution.

1. Are the two solutions of the same concentration?
2. Compare the mass % of the two solutions.

Answer:

1. No.
2. Rameshs solution concentration

Mass % = \(\frac{\text { Mass of solute }}{\text { Mass of solution }} \times 100\)

⇒ \(\frac{10 \mathrm{~g}}{(10+100) \mathrm{g}} \times 100\)

⇒ \(\frac{10}{110} \times 100\)

⇒ \(\frac{100}{11}=9.09 \%\)

⇒ \(9.1 \%\)

Sarika s solution concentration

⇒ \(\text { Mass } \%\)

⇒ \(\frac{10}{100} \times 100=10 \%\)

The solution prepared by Ramesh has less percentage by mass than that of Sarika.

Question 9.

1. Under which category of mixtures will you classify alloys and why?
2. Whether a solution is always liquid or not. Comment.
3. Can a solution be heterogeneous?

Answer:

1. Alloys are homogeneous mixtures of metals, or non-metals because
   1. It shows the properties of its constituents, and
   2. It has variable composition, for example., brass is considered a mixture because it shows the properties of its constituents, copper and zinc; and it has a variable composition.
2. A solution is generally a liquid, not always, for example., alloys are known to be solid solutions.
3. The term solution is generally used for ‘true solution. In this case, the solution is always homogeneous.
4. In the case of a colloidal solution, that is not a true solution, the solution is heterogeneous.

Question 10. Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 g of water to form a saturated solution).

1. What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 g of water at 313 K?
2. Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.
3. Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature?
4. What is the effect of a change in temperature on the solubility of a salt?

Answer:

1. At 313 K, solubility of potassium nitrate in 100 g of water = 62

Solubility = \(\frac{\text { Mass of solute }}{\text { Mass of solvent }} \times 100\)

Mass or solute = \(\frac{\text { Solubility } \times \text { Mass of solvent }}{100}\)

∴ Mass of potassium nitrate = \(\frac{62 \times 50}{100}=31 \mathrm{~g}\)

Hence, 31g of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 30 g of water at 313 K.

2. The amount of potassium chloride that should be dissolved in water to make a saturated solution increases with temperature.

Thus, as the solution cools, some of the potassium chloride will precipitate out of the solution and form crystals.

3. The solubility of the salts at 293 K are:

Potassium nitrate 32; Sodium chloride 36, Potassium chloride 33; Ammonium chloride 37 Thus, ammonium chloride has the maximum solubility (37) at 293 K.

4. The solubility of a solid (salt) decreases with a fall in temperature, while it increases with a temperature rise.

 Class 9 Science Chapter 2 Is Matter Around Us Pure Short Answer Type Questions

Question 1. An element is sonorous and highly ductile. Under which category would you classify this element? What other characteristics do you expect the element to possess?
Answer:

This element is categorised as a ‘metal’ because metals are sonorous and ductile. Other properties or characteristics possessed by this element are expected to be the following:

1. They possess metallic lustre.
2. They are good conductors of heat and electricity.
3. They are malleable.
4. They have high tensile strength.
5. They have high densities and high melting points/boiling points too.

Question 2. Classify the following as elements, compounds and mixtures.

1. Gold
2. Marble
3. Air
4. Milk
5. Sugar

Answer:

• Element – Gold
• Compound – Marble and sugar
• Mixture – Air and milk

Question 3. How will you prove that water is a compound?
Answer:

Water is considered to be a compound due to the following reasons:

1. Hydrogen and oxygen are present in a fixed ratio of 1:8 by mass in water.
2. Water has a fixed boiling point, i.e. 100°C at 1 atmospheric pressure.
3. The constituents of water (H and O) cannot be separated from it by simple physical methods.
4. The properties of water are entirely different from those of its constituents, i.e. hydrogen and oxygen.

Question 4. Sucrose (sugar) crystals obtained from sugarcane and beetroot are mixed. Will it be a pure substance or a mixture? Give reasons for the same.
Answer:

It is a pure substance because the chemical composition of sugar crystals is the same irrespective of its source.

Question 5. Define a solution. Give an example of

1. Gas in liquid solution.
2. Gas in gas solution.

Answer:

The solution is a homogeneous mixture of two or more substances, for example., salt in water.

1. CO₂ dissolved in water
2. Air

Question 6. What types of mixtures are represented by the following?

1. Carbon dioxide gas dissolved in water.
2. Air containing suspended particles.
3. Soap bubbles formed by blowing air into the soap solution.
4. Water in milk.

Answer:

1. Homogeneous
2. Heterogeneous
3. Heterogeneous
4. Heterogeneous

Question 7. When egg albumin is added to water the clear solution becomes turbid. How would you test to confirm that it is a colloidal solution?
Answer:

Filter the contents of test tubes. No residue is left on the filter paper, but the filtrate obtained is translucent. Since a colloid cannot be separated by filtration, it is a colloid.

Question 8. Give some examples of the Tyndall effect observed in your surroundings.
Answer:

1. Sunlight passes through the canopy of a dense forest.
2. A fine beam of light enters a room through a small hole.

Question 9. Why does the sky appear blue?
Answer:

So The blue colour of the sky is due to the scattering of light by fine dust particles (i.e. Tyndall effect) which are present in the atmosphere.

Question 10. Give reasons:

1. The path of a beam of light is not visible through a true solution.
2. Particles of suspension can be seen with the naked eye.

Answer:

1. The path of a beam of light is not visible through a true solution because particles of a true solution are not large enough to scatter light.
2. The particle size of the suspension is greater than 100 nm. So, they can be seen with the naked eye.

Question 11. On dissolving chalk powder in water, a suspension is obtained. Give any four reasons to support the fact that the mixture so obtained is a suspension only.
Answer:

So It is supported by the following reasons:

1. White particles of chalk powder can be seen with the naked eye.
2. The particles can be separated by ordinary filter paper.
3. Upon shaking, white turbidity reappears in the solution.
4. Light can be passed through this solution, which suggests that it shows the Tyndall effect.

Question 12. Smoke and fog both are aerosols. In what way are they different?
Answer:

In both smoke and fog, the dispersion medium is the same, i.e. gas, but they differ in the dispersed phase.  In smoke, the dispersed phase is solid while in fog, the dispersed phase is liquid.

Question 13. How do sol and gel differ from each other? Give one example for each.
Answer:

• The sol is a colloid in which tiny solid particles are dispersed in a liquid medium. Examples of sol are ink and soap solution.
• The gel is a semi-solid colloid in which liquid particles are dispersed in a solid. Examples of gel are jellies and gelatin.

Question 14. Classify the following as physical or chemical properties.
Answer:

1. The composition of a sample of steel is 98% iron, 1.5% carbon and 0.5% other elements.
2. Zinc dissolves in hydrochloric acid with the evolution of hydrogen gas.
3. Metallic sodium is soft enough to be cut with a knife.
4. Most metal oxides form alkalis on interacting with water.

Answer:

1. Physical
2. Chemical
3. Physical
4. Chemical

Question 15. On heating, calcium carbonate gets converted into calcium oxide and carbon dioxide.

1. Is this a physical or a chemical change?
2. Can you prepare one acidic or one basic solution by using the products formed in the above process? If so, write the chemical equation involved.

Answer:

The phenomenon given in question is a chemical change because the composition of the product formed is different from the substance taken.

The reaction involved is \(\mathrm{CaCO}_3→{\Delta} \mathrm{CaO}+\mathrm{CO}_2\)

Yes, 1.  \(\mathrm{CaO}+\mathrm{H}_2 \mathrm{O} \longrightarrow \underset{\text { Calcium hydroxide } \\\text { (Basic solution) }}{\mathrm{Ca}(\mathrm{OH})_2}\)

2. \(\mathrm{CO}_2+\mathrm{H}_2 \mathrm{O} \longrightarrow \underset{\text { Carbonic acid } \\ \text { (Acidic solution) }}{\mathrm{H}_2 \mathrm{CO}_3}\)

Question 16. A child eats chocolate and digests it. In doing so, some physical and chemical changes take place. Identify the changes.
Answer:

Physical change Breaking of chocolate into small pieces.

Chemical change Digestion of chocolate.

Question 17. Explain why particles of colloidal solution do not settle down when left undisturbed, while in the case of a suspension, they do.
Answer:

Colloidal particles are smaller in size. The force of gravity which is acting on colloidal particles is encountered and they do not settle down. However the particles of suspension are larger, so they settle down under the influence of gravity.

Question 18. A solution made by dissolving 50 g of glucose in 250 g of water. Calculate the concentration of this solution in mass percentage.
Answer:

Mass percentage \(=\frac{\text { Mass of glucose }}{\text { Mass of glucose }+ \text { Mass of water }} \times 100\)

⇒ \(\frac{50}{50+250} \times 100\)

⇒ \(\frac{50}{300} \times 100=\frac{50}{3}=16.66 \%\)

Question 19. What volume of ethyl alcohol and water must be mixed to prepare 250 mL of 60% by volume of alcohol in water?
Answer:

Let the volume of ethyl alcohol be x mL

Concentration of solution

⇒ \(\frac{\text { Volume of solvent (ethyl alcohol) }}{\text { Volume of solution }} \times 100\)

⇒ \(60=\frac{x}{250} \times 100\)

⇒ \(x=\frac{250 \times 60}{100}=150 \mathrm{~mL}\)

Question 20. Calculate the mass of potassium sulphate required to prepare its 10 per cent (mass per cent) solution in 100 g of water.
Answer:

∴ \(\text { Mass } \%=\frac{\text { Mass of solute }}{\text { Mass of solution }} \times 100\)

Let the mass of potassium sulphate (solute) = xg

Then, mass of solution = (100 + x) g

⇒ Mass %=10= \(\frac{x}{(x+100)} \times 100\)

⇒ \(1=\frac{x \times 10}{(x+100)} \Rightarrow x+100=10 x\)

⇒ 9x = 100

∴ \(x=\frac{100}{9}=11.1 \mathrm{~g}\)

Question 21. Non-metals are usually poor conductors of heat and electricity. They are non-lustrous, non-sonorous, non-malleable and are coloured.

1. Name a lustrous non-metal.
2. The allotropic form of a non-metal is a good conductor of electricity. Name the allotrope.
3. Name a non-metal which is known to form the largest number of compounds.
4. Name a non-metal other than carbon which shows allotropy
5. Name a non-metal which is required for combustion.
6. Name a non-metal that forms common salt with sodium.

Answer:

1. Iodine
2. Graphite (Carbon)
3. Carbon
4. Phosphorus
5. Oxygen
6. Chlorine

Question 22. Classify the substances given below into elements and compounds.

Answer:

Question 23. Which of the following are not compounds?

1. Chlorine gas
2. Potassium
3. Iron
4. Iron sulphide
5. Aluminium
6. Iodine
7. Carbon
8. Carbon monoxide

Answer:

1. Chlorine gas
2. Potassium
3. Iron
4. Aluminium
5. Iodine
6. Carbon

Substances mentioned above are the elements, not compounds. Cl₂ gas is a molecular element.

Question 24. Classify the following mixtures as homogeneous and heterogeneous.

1. Tincture of iodine
2. Smoke
3. Brass
4. Sugar solution

Answer:

1. Homogeneous
2. Heterogeneous
3. Homogeneous
4. Homogeneous

Question 25. Tell whether each of the following properties describes a homogeneous mixture, a solution, a heterogeneous mixture, a compound or an element.

1. A homogeneous liquid which leaves a solid residue on boiling.
2. A cloudy liquid which after some time appears more cloudy towards the bottom.
3. A colourless liquid which boils at a definite temperature and can be decomposed into simpler substances.

Answer:

1. A solution (a solid like salt dissolved in water from which water evaporates on boiling, leaving a solid residue, salt).
2. A heterogeneous mixture in which suspended particles start settling down at the bottom (muddy water).
3. A compound.

Question 26. What would you observe when

1. A saturated solution of potassium chloride prepared at 60°C is allowed to cool to room temperature.
2. A mixture of iron filings and sulphur powder is heated strongly.

Answer:

1. Crystals of potassium chloride are formed because solubility decreases with a decrease in temperature.
2. The compound iron sulphide is formed.

Answer:

Question 27. Why copper sulphate solution in water does not show the Tyndall effect, but a mixture of water and milk shows?
Answer:

• The solution of copper sulphate in water is a true solution. In a true solution, the solute particles are so small that they cannot scatter light falling on them.
• Hence, copper sulphate solution in water does not show the Tyndall effect.
• A mixture of water and milk is a colloid and in a colloidal solution, the particles are big enough to scatter light. So, the mixture of water and milk shows the Tyndall effect.

Question 28. Determine whether each of the following changes is physical or chemical. Give a reason for your answer.

1. A balloon filled with hydrogen gas explodes upon contact with a spark.
2. Copper turns green on exposure to air and water.

Answer:

1. Chemical change Hydrogen gas burns to form water.
2. Chemical change Copper combines with oxygen from air and water to form a copper oxide which has a green colour.

Question 29. Can physical and chemical changes occur together? Illustrate your answer.
Answer:

• In some cases, physical and chemical changes occur together. One such example is the burning of candles. The solid wax present in the candle first changes into a liquid state and then into a vapour state.
• Both these changes are physical. The wax vapours then combine with oxygen in the air to form a mixture of carbon dioxide and water. This involves a chemical change.
• The unburnt wax vapours again change first to the liquid state and finally to the solid state. This interconversion of states is a physical change. Thus, the burning of a candle involves both physical and chemical changes.

Question 30. Calculate the mass of sodium sulphate required to prepare its 20% (mass per cent) solution in 100 g of water.
Answer:

Mass % of sodium sulphate solution = 20%

Mass of the solvent = 100g

Let the mass of solute (sodium sulphate) = xg

Applying the formula,

⇒ \(\text { Mass } \%=\frac{\text { Mass of solute }}{\text { Mass of solution }} \times 100\)

⇒ \(20=\frac{x \mathrm{~g}}{(x+100) \mathrm{g}} \times 100\)

⇒ 20 (x+ 100) =100x

⇒ 20x + 2000 =100 xH2x

⇒ 100x – 20x = 2000

⇒ 80x = 2000

∴ \(x=\frac{2000}{80}=25 \mathrm{~g}\)

Mass of sodium sulphate = 25 g

Question 31. 110 g of salt is present in 550 g of solution. Calculate the mass percentage of the solution.
Answer:

Mass percentage of solution

⇒ \(=\frac{\text { Mass of solute }}{\text { Mass of solution }} \times 100\)

Mass of solute = 110 g [given]

Mass of solution = 550 g [given]

Mass percentage = \(\frac{110}{550} \times 100\)

= 20 %

Question 32. List the points of difference between homogeneous and heterogeneous mixtures. Or Differentiate between homogeneous and heterogeneous mixtures with examples.
Answer:

The main points of differences between the homogeneous and heterogeneous mixtures are as follows:

Question 33. To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.
Answer:

Mass of solute (NaCl) =36 g

Mass of solvent (H₂O) = 100 g

Mass of solution = 36 +100=136 g

Concentration (by mass) of the solution

⇒ \(\frac{\text { Mass of solute }}{\text { Mass of solution }} \times 100\)

⇒ \(\frac{36}{136} \times 100\)

= 26.47%

Question 36. Classify the following as chemical or physical changes:

• Cutting of trees,
• Melting of butter in a pan,
• Rusting of almirah,
• Boiling of water to form steam,
• The passing of electric current through water and the water breaking down into hydrogen and oxygen gases,
• Dissolving common salt in water,
• Making a fruit salad with raw fruits, and
• Burning of paper and wood.

Answer:

Physical changes

• Cutting of trees,
• Melting of butter in a pan, b
• Oiling of water to form steam,
• Dissolving common salt in water, and
• Making a fruit salad with raw fruits

Chemical changes

• Rusting of almirah
• The passing of electric current through water and breaking down of water into hydrogen and oxygen gases.
• Burning of paper and wood.

Question 35. Classify each of the following as a homogeneous or heterogeneous mixture. Soda water, wood, air, soil, vinegar, filtered tea.
Answer:

Homogeneous mixtures of Air, soda water, vinegar, and filtered tea.

Heterogeneous mixtures of Wood, and soil.

Note: Homogeneous mixtures have the same composition throughout, while the composition of heterogeneous mixtures is not uniform.

Question 36. How would you confirm that a colourless liquid given to you is pure water?
Answer:

• Take a given colourless liquid in a beaker and suspend a thermometer into it. Place the beaker on a wire gauze and start heating with the help of a burner.
• Note down the temperature at which water begins to boil. If the given liquid boils at 100°C, the liquid will be pure water as the boiling point of pure water is 100°C.

Question 37. Which of the following materials fall in the category of pure substance?

1. Ice
2. Milk
3. Iron
4. Hydrochloric acid
5. Calcium oxide
6. Mercury
7. Brick
8. Wood
9. Air

Answer:

Ice, iron, calcium oxide and mercury are pure substances as they have definite composition. Hydrochloric acid is a mixture of hydrogen chloride gas and water, so it is a mixture and not a pure substance.

Question 38. Identify the solutions among the following mixtures.

1. Soil
2. Seawater
3. Air
4. Coal
5. Soda water

Answer:

Sea water, air and soda water, as these are homogeneous mixtures of two or more substances.

Note: Sea water is also considered a heterogeneous solution.

Question 39. Which of the following will show the Tyndall effect?

1. Salt solution
2. Milk
3. Copper sulphate solution
4. Starch solution

Answer:

Milk and starch solution being a colloid will show the Tyndall effect, while salt solution and copper sulphate solution are true solutions that will not show the Tyndall effect due to the small size of their particles.

Question 40. Classify the following into elements, compounds and mixtures.

1. Sodium
2. Soil
3. Sugar solution
4. Silver
5. Calcium carbonate
6. Tin
7. Silicon
8. Coal
9. Air
10. Soap
11. Methane
12. Carbon dioxide
13. Blood

Answer:

Elements Sodium, silver, tin and silicon.

Compounds Calcium carbonate, methane, carbon dioxide and soap.

Mixtures Soil, sugar solution, coal, air, blood and soap. Soap is a compound, but to make it suitable for specific purposes, various substances are added to it. Then, it becomes a mixture.

Question 41. Which of the following are chemical changes?

1. Growth of a plant
2. Rusting of iron
3. Mixing of iron filings and sand
4. Cooking of food
5. Digestion of food
6. Freezing of water
7. Burning of a candle

Answer:

GrowtlTof a plant, rusting of iron, cooking of food, digestion of food and burning of a candle are chemical changes.

Question 42. Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
Answer:

Method Of Preparation Of Tea

1. Take some water (solvent) in a pan and heat it.
2. Add some sugar (solute) and boil to dissolve the sugar completely, the obtained homogeneous mixture is called a solution.
3. Add tea leaves (or tea) to the solution and boil the mixture.
4. Now add milk and boil again.
5. Filter the mixture through the tea stainer and collect the filtrate or soluble substances, i.e. tea in a cup. The insoluble tea leaves are left behind as residue in the strainer.

 Class 9 Science Chapter 2 Is Matter Around Us Pure Very Short Answer Type Questions

Question 1. State any one difference between pure and impure substances.
Answer:

The pure substance contains only one kind of particle. All the elements and compounds are pure substances. An impure substance contains two or more different kinds of particles. All the mixtures are impure substances.

Question 2. Identify homogeneous mixtures from the following. Soda water, soil, vinegar, unfiltered tea.
Answer: Soda water and vinegar.

Question 3. Is ice water a homogeneous or heterogeneous substance? Is it a pure or impure substance?
Answer:

Ice water is a heterogeneous, but pure substance as ice is made up of water only, which contains only one kind of particle.

Question 4. The ‘sea water’ can be classified as a homogeneous as well as a heterogeneous mixture. Comment.
Answer:

Sea water is called a homogeneous mixture as it contains dissolved salts in it. It may be called a heterogeneous mixture as it contains various insoluble components too such as sand, microbes, shells made up of calcium carbonate and so many other things.

Question 5. Is fresh air free of dust particles and impurities of all other kinds, a pure substance?
Answer:

No, only elements and compounds are pure substances. Air is a mixture of gases and so, not a pure substance.

Question 6. Give one test to show that brass is a mixture and not a compound.
Answer:

The melting point of brass is not definite. So, it is not a compound but it is an alloy (mixture) of copper and zinc.

Question 7. Tincture of iodine has antiseptic properties. How is it prepared?
Answer: A tincture of iodine is prepared by dissolving iodine in alcohol.

Question 8. What are the two components of a solution?
Answer:

The two components of a solution are:

1. Solute
2. Solvent

Question 9. What is meant by the concentration of a solution?
Answer:

The amount of solute present in a given amount (mass or volume) of solution (or solvent) is known as the concentration of solution.

Question 10. Based on which factor, a solution is said to be dilute, concentrated or saturated?
Answer: Amount of solute present in it.

Question 11. Why particles in a true solution cannot be seen with the naked eye?
Answer: Particles of a true solution are very small in size (less than 1nm), hence they are not visible.

Question 12. The particle size of a substance in water is 200 nm. What is the nature of the solution?
Answer:

As the particle size of a substance is greater than 100 nm, the solution will be a suspension.

Question 13. A student mixes the white of an egg with water and stirs it well. After some time, what did he observe?
Answer: He observed that a cloudy solution is formed.

Question 14. Do suspensions show the property of the Tyndall effect?
Answer:

Yes, suspensions show the property of the Tyndall effect because their particles are too large and scatter the light.

Question 15. State which of the following solutions exhibits the Tyndall effect. Starch solution, sodium chloride solution, tincture of iodine, smoke.
Answer: Starch solution and smoke.

Question 16. ‘Tyndall effect can be observed when sunlight passes through the canopy of dense forest’. Explain, how this occurs.
Answer:

This is because the forest contains mist which in turn contains tiny droplets of water that act as particles of colloid dispersed in air.

Question 17. What are the favourable qualities given to gold when it is alloyed with copper or silver to make ornaments?
Answer:

When alloyed with copper or silver, the gold becomes harder and stronger and its brittleness decreases and becomes suitable for making ornaments.

Question 18. Which of the tubes in Figures (1) and (2) will be more effective as a condenser in the distillation apparatus?

Answer:

Condenser (1) will be more effective in the distillation apparatus because the beads present will provide more surface area for cooling and condensation of the vapour occurs repeatedly by passing through it.

Question 19. How will you justify that the rusting of iron is a chemical change?
Answer:

In a chemical change, a new substance is formed and rust is different from iron. Iron is an element while rust is hydrated oxide of iron (Fe₂O₃  xH₂O). Thus, the formation of rust from iron is a chemical change.

Question 20. Choose the chemical change out of the following. Digestion of food, freezing of water, glowing of electric lamp and a mixture of iron filings with sulphur.
Answer: Digestion of food.

Question 21. What is meant by a substance?
Answer:

A substance which is made up of a single type of particle is called a pure substance, For example., hydrogen, oxygen, sulphur, etc.

Question 22. Try segregating the things around you as pure substances or mixtures.
Answer:

Pure substance- Sugar, common salt, rubber. Mixture- Wood, coal, milk, soap, soil. The soap that we use in our daily lives is a mixture.

Is Matter Around Us Pure Multiple Choice Questions

Question 1. Which of the following is a pure substance?

1. Air
2. Distilled water
3. Steel
4. Brass

Answer: 2. Distilled water

Any substance that contains only one type of particle (for example., molecules/atoms etc.) is said to be a pure substance. Among the given options, distilled water has only one type of particle (i.e. H₂O molecules) while air is a mixture of various gases, steel and brass are alloys.

∴ Hence (2) is the correct option.

Question 2. Which of the following properties does not prove that water is a compound?

1. The ratio of hydrogen and oxygen by mass in water is fixed
2. Water has a fixed boiling point (b.p.)
3. Simple physical methods cannot separate the constituents of water
4. Distilled water and tap water have the same taste and constituents

Answer: 4. Distilled water and tap water have the same taste and constituents

• Distilled water and tap water have different tastes and different constituents.
• Distilled water has pure H₂O molecules while tap water may contain other molecules also.
• The ratio of hydrogen and oxygen by mass remains 1:8 in all the H₂O molecules.
• They have fixed b.p. and cannot be separated into their constituents by simple physical methods.

∴  (4) is the correct option.

Question 3. Two elements X and Y combine to give a product Z. The correct statement about Z is

1. Z has more mass than that of X
2. Z has less mass than that of X
3. Z has less mass than that of Y
4. Z show the same properties as of X and Y

Answer: 1. Z has more mass than that of X

Product Z is formed by the combination of X and Y, thus has more mass than of X and Y separatly. Also Z is entirely a new product, thus cannot show same properties, as of X and Y

Question 4. During the purification of water, which of the following step(s) is incorrect?

1. Sedimentation of water
2. Loading of water with alum
3. Electrolysis of water
4. Chlorination of water

Answer: 3. Electrolysis of water

1. During the purification of water
2. Sedimentation is done to remove suspended particles (for example., solids).
3. Loading with alum is done to remove small particles like clay present in colloidal state.
4. Electrolysis is not done, as it dissociates the water molecules in H₂(g) and O₂(g).
5. Chlorination is done to kill the bacteria’s (e.g use of bleaching powder).

Hence, (3) is the correct option.

Question 5. The pair of substance (s) that can be separated by sublimation is/are

1. NH₄Cl and salt
2. sugar solution in water
3. salt solution in water
4. kerosene oil and water

Answer: 1. NH₄Cl and salt

A mixture of ammonium chloride and salt can be separated by sublimation as NH₄Cl changes to vapour directly, i.e. without changing in liquid state while salt does not.

Hence, (1) is the correct option.

Question 6. To prepare iron-sulphide by heating a mixture of iron filings and sulphur powder, we commonly use

1. Petri-dish
2. Water-glass
3. China-dish
4. Beaker

Answer: 3. China-dish

We commonly use Chinese for heating because it can bear high temperatures on heating the mixture.

Question 7. Which of the following substances cannot be broken down by a chemical method?

1. Ammonia (NH₃)
2. Helium (He)
3. Methane (CH₄)
4. Water (H₂O)

Answer: 2. Helium (He)

Helium cannot be broken down by a chemical method as it is an element, while other substances are compounds and can dissociate in their constituents because ammonia is made by two elements nitrogen and hydrogen, methane is made by carbon and hydrogen and water is made by hydrogen and oxygen.

Question 8. Smoke and fog differ from each other because

1. They have different dispersion medium
2. They have different dispersed phase
3. Both (1) and (2)
4. None of these

Answer: 2. They have different dispersed phase

Smoke and fog both have the same dispersion medium but they differ in dispersed phase. In smoke, the dispersed phase is solid while in fog, the dispersed phase is liquid.

Hence, (2) is the correct option.

Question 9. Which of the following will not show the Tyndall effect?

1. Smoke
2. Foam
3. Jelly
4. Salt solution

Answer: 4. Salt solution

The salt solution will not show the Tyndall effect as it is a true solution and particles of salt solution are very small (size < 1 nm). So, these cannot scatter a beam of light and, hence do not show the Tyndall effect.

Question 10. Which of the following is an example of emulsion?

1. Mist
2. Milk
3. Face cream
4. Both (2) and (3)

Answer: 4. Both (2) and (3)

Milk and face cream, both are emulsions of liquid in liquid. Mist is an aerosol, present in our atmosphere. Hence, is the correct option.

Question 11. Which of the following is a physical change?

1. Rusting of iron
2. Formation of water vapours from water
3. Cooking of food
4. Formation of water from hydrogen and oxygen

Answer: 2. Formation of water vapours from water

Formation of water-vapours from water is a physical change, as we can get back the water by simple physical method (i.e. condensation) while all others are examples of chemical changes because products formed can not give back the former reactant (i.e. substance) by physical methods.

Hence, (2) is the correct option.

Question 12. The correct statement about an article made up of iron getting rusted, is/are

1. The process is called corrosion and is a physical change
2. The process is called dissolution and is a physical change
3. The process is called corrosion and is a chemical change
4. The process is called dissolution and is a chemical change

Answer: 3. The process is called corrosion and is a chemical change

The rusting of an article made up of iron is called corrosion. Corrosion is a chemical change because rust is a chemical compound (product) which has different properties and formula than that of reactants.

∴ \(4 \mathrm{Fe}+3 \mathrm{O}_2+x \cdot \mathrm{H}_2 \mathrm{O} \longrightarrow \underbrace{2 \mathrm{Fe}_2 \mathrm{O}_3 \cdot x \cdot \mathrm{H}_2 \mathrm{O}}_{\text {Rust }}\)

Hence, (3) is the correct option.

Question 13. Which of the following is considered to be a pure substance?

1. Sodium chloride
2. Muddy water
3. Granite
4. Milk of magnesia

Answer: 1. Sodium chloride

Question 14. What is the sulphur?

1. A metal
2. A metalloid
3. A non-metal
4. None of these

Answer: 3. A non-metal

Question 15. Which of the following elements is a non-metal?

1. Fe
2. Na
3. Cu
4. Cl

Answer: 4. Cl

Question 16. Which one of the following is a metalloid?

1. Na
2. Fe
3. Cu
4. As

Answer: 4. As

Question 17. In which of the following the constituents are present in any ratio?

1. Compound
2. Mixture
3. Colloid
4. Solution

Answer: 4. Solution

Question 18. Which of the following is an example of a homogeneous substance?

1. Polluted air
2. Muddy water
3. Salt solution
4. None of the above

Answer: 3. Salt solution

Question 19. Which of the following is not an example of a colloidal solution?

1. Glue
2. Milk
3. Salt solution
4. Blood

Answer: 4. Blood

Question 20. Which one of the following statements is suitable (correct) for the mixture of sulphur and carbon disulphide?

1. Heterogeneous mixture and represent Tyndall effect
2. Homogeneous mixture and represent Tyndall effect
3. Heterogeneous mixture but does not show the Tyndall effect
4. Homogeneous mixture but does not show the Tyndall effect

Answer: 4. Homogeneous mixture but does not show Tyndall effect

Is Matter Around Us Pure Fill In The Blanks

Question 1. A colloid is a mixture and its components can be separated by the technique known as
Answer: Heterogeneous, centrifugation

Question 2. Ice, water and water vapour look different and display different properties, but they are the same.
Answer: Physical, chemically

Atoms And Molecules Multiple Choice Questions

Question 1. A sample of pure water, irrespective of its source, contains 11.1% hydrogen and 88.9% oxygen. The data supports

1. Law of multiple proportions
2. Law of reciprocal proportions
3. Law of constant proportions
4. Law of conservation of mass

Answer: 3. law of constant proportions

Water obtained from any source contains hydrogen and oxygen in the same proportion by mass. Hence, the data supports the law of constant proportion.

Question 2. If 12 g of C is burnt in the presence of 32 g of O₂, how much CO₂ will be formed?

1. 40 g CO₂
2. 44 g CO₂
3. 30 g CO₂
4. 22 g CO₂

Answer: 2. 44 g CO₂

CO₂ is formed by the following reaction.

⇒ \(\underset{12 \mathrm{~g}}{\mathrm{C}}+\underset{32 \mathrm{~g}}{\mathrm{O}_2} \longrightarrow \mathrm{CO}_2\)

By the law of conservation of mass,

Mass of reactants = Mass of products

Mass of C+ Mass of O₂ = Mass of CO₂

12 g + 32 g = 44 g

Therefore, 44 g of CO₂ will be formed.

Question 3. The formula of chloride of a metal M is MCl₃, then the formula of the phosphate of metal M will be

1. M₂PO₄
2. MPO₄
3. M₂(PO₄)₃
4. M₃PO₄

Answer: 2. MPO4

The valency of M is +3

∴ The formula of phosphate of metal M will be MPO₄.

Question 4. How many moles are present in 11.5 g of sodium?

1. 0.5 mol
2. 5.0 mol
3. 0.05 mol
4. 1.5 mol

Answer: 1. 0.5 mol

23 g of Na present in = 1 mol

11.5 g of Na present = \(\frac{1}{23} \times 11.5\)

= 0.5 mol.

Question 5. Which one of the following statements is true?

1. Mass of 0.5 mole of N₂ gas > mass of 0.5 mole of N atoms
2. Mass of 0.5 mole of N₂ gas =mass of 0.5 mole of O₂ gas
3. Mass of 0.5 mole of N₂ gas < mass of 0.5 mole of N atoms
4. Mass of 0.5 mole of N₂ gas = mass of 0.5 mole of N atoms

Answer: 1. Mass of 0.5 mole of N₂ gas > mass of 0.5 mole of N atoms

1. 1 mole of N₂ gas has mass = 28 g
2. 0.5 mole of N₂ gas has mass = 28 × 0.5 =14 g
3. 1 mole of N atoms have mass = 14 g
4. 0.5 mole of N atoms have mass =14 × 0.5 = 7g

∴ Mass of 0.5 mole of N₂ gas > mass of 0.5 mole of N atoms.

Question 6. Which of the following represents 1 amu?

1. Mass of hydrogen molecule 1
2. \(\frac{1}{12}\)th of mass of C-12 atom 12
3. Mass of 0-12 atom
4. Mass of C-12 atom

Answer: 2. \(\frac{1}{12}\)th of mass of C-12 atom 12

Question 7. A 0.24 g sample of a compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen.

What will be the percentage composition of the compound by weight?

1. Boron = 40%, oxygen = 60%
2. Boron = 60%, oxygen = 40%
3. Boron = 35%, oxygen = 55%
4. Boron = 20%, oxygen = 30%

Answer: 1. Boron = 40%, oxygen = 60%

We know that the mass % of any element in a compound

⇒ \(\frac{\text { mass of element }}{\text { mass of compound }} \times 100\)

⇒ \(\text { Mass } \% \text { of boron }=\frac{0.096}{0.24} \times 100=40 \%\)

⇒ \(\text { Mass } \% \text { of oxygen }=\frac{0.144}{0.24} \times 100=60 \%\)

Question 8. Calculate the molecular mass of Al₂(SO₄)₃.

1. 342 u
2. 242 u
3. 249.5 u
4. 288 u

Answer: 1. 342 u

The molecular mass of Al, (SO₄)₃

= 2 × Atomic mass of Al + 3 [Atomic mass of S + 4 × (Atomic mass of O)]

= 2 × 27. 0 u + 3 × (32. 0 u + 4 × 16.0 u)

= 54 u + 3(32 + 64)u = 54 + 3 × 96u

= 54 + 288 u =342u

Question 9. What will be the mass of 5 mole of SO₂?

1. 310 g
2. 320 g
3. 290 g
4. 120 g

Answer: 2. 320 g

Molecular mass of SO₂ = 64 g

⇒ \(\text { Number of mole }=\frac{\text { Mass of } \mathrm{SO}_2(\mathrm{~g})}{\text { Molecular mass of } \mathrm{SO}_2(\mathrm{~g})}\)

Mass of SO₂ (g) = number of mole x molecular mass of SO₂

= 5 × 64

= 320 g

Question 10. Calculate the mass in g of 2NA molecules of CO₂,

1. 88g
2. 22g
3. 44g
4. None of these

Answer: 1. 88g

NA molecules of CO₂ have molecular mass =44 g.

∴ 2 N A molecules of CO₂ have a molecular mass

= 44 x 2 = 88 g

Question 11. How many molecules are in 5.23 g of glucose (C₆H₁₄O₆)?

1. 1.75 x 10²¹
2. 1.75 x 10²²
3. 1.65 x 10²²
4. None of the above

Answer: 2. 1.75 x 10²²

180g glucose has =NA molecules.

∴ 5.23 g glucose has = \(\frac{5.23 \times 6.022 \times 10^{23}}{180}\)

= 1.75 x 10²² molecules.

Question 12. “Mass can neither be created nor destroyed in a chemical reaction” is defined

1. Law of constant proportion
2. Law of conservation of mass
3. Law of reciprocal proportions
4. Law of multiple proportions

Answer: 2. Law of conservation of mass

Question 13. The percentage of copper and oxygen in samples of CuO obtained by different methods was found to be the same. They illustrate the law of

1. Conservation of mass
2. Multiple proportions
3. Constant proportion
4. Reciprocal proportion

Answer: 3. Constant proportion

Question 14. The percentage of hydrogen in H₂O is

1. 11.12
2. 21.12
3. 20.60
4. 80.0

Answer: 1. 11.12

Question 15. The mass of one C atom is

1. 6.022 × 10²³g
2. 12g
3. 6 g
4. 1.99 × 10^-23g

Answer: 4. 1.99 × 10^-23g

Question 16. The correct symbol for silver is

1. Ag
2. Au
3. A1
4. Si

Answer: 1. Ag

Question 17. The chemical symbol P stands for

1. Phosphorus
2. Potassium
3. Polonium
4. Platinum

Answer: 1. Phosphorus

Question 18. Adding electrons to an atom will result in a

1. Anion
2. Cation
3. Molecule
4. Salt

Answer: 3. Molecule

Question 19. One gram of which of the following contains the largest number of oxygen atoms?

1. O₃
2. O
3. O₂
4. All contain same

Answer: 1. O₃

Question 20. How many molecules are present in one gram of hydrogen?

1. 6.02 × 10²³
2. 1.5 × 10²⁴
3. 3.01 × 10²³
4. 4.5 × 10²³

Answer: 3. 3.01 × 10²³

Question 21. Find out the molecular mass of H₂O.

1. 16μ
2. 18μ
3. 24μ
4. 72μ

Answer: 2. 18μ

Question 22. Write down the names of compounds represented by the following formulae.

1. Al₂ (SO₄)₃
2. CaCl₂
3. K₂SO₄
4. KNO₃
5. CaCO₃

Answer:

1. Aluminium sulphate [Al₂(SO₄)₃]
2. Calcium chloride (CaCl₂)
3. Potassium sulphate (K₂SO₄)
4. Potassium nitrate (KNO₃)
5. Calcium carbonate (CaCO₃)

Question 23. What is meant by the term chemical formula?

1. Al₂(SO₄)₃
2. CaCl
3. K2SO₄
4. KNO₃
5. CaCO₃

Answer:

1. OD Aluminium sulphate [Al₂(SO₄)₃]
2. Calcium chloride (CaCl₂)
3. Potassium sulphate (K₂SO₄)
4. Potassium nitrate (KNO₃)
5. Calcium carbonate (CaCO₃)

Atoms And Molecules Fill In The Blanks

Question 1. In a chemical reaction, the sum of the masses of the reactants and products remains unchanged. This is called___
Answer: The law of conservation of mass

Question 2. A group of atoms carrying a fixed charge on them is called___
Answer: Polyatomic ion

Question 3. The formula unit mass of Ca₃(PO₄)₂ is___
Answer: 310 u

Question 4. The formula of sodium carbonate is … and that of ammonium sulphate is ___
Answer: Na₂CO₃; (NH₄)₂SO₄

Class 9 Science Chapter 3 Atoms And Molecules Long Answer Type Questions

Question 1.

1. Explain why the number of atoms in one mole of hydrogen gas is double the number of atoms in one mole of helium gas.
2. Explain atomic mass unit.
3. How many atoms are present in
   1. MnO₂ molecule
   2. CO molecule?

Answer:

1. Hydrogen gas exists as a diatomic molecule, i.e. each hydrogen gas molecule (H₂) has two atoms. While helium gas exists as a monoatomic particle that is its atoms exist individually.
   1. Thus, one mole of hydrogen gas has a double number of atoms as compared to one mole of helium gas.
2. The unit of mass equivalent to the twelfth part of the mass of the C-12 isotope of carbon is called atomic mass unit (amu) or unified mass (u).
3. In the MnO₂ molecule, three atoms are present: one manganese atom and two oxygen atoms.
   1. In a CO molecule, two atoms are present: one carbon atom and one oxygen atom.

Question 1. A 0.24 g sample of a compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound by weight.
Answer:

Mass of the compound = 0.24 g,

Mass of boron = 0.096 g

Mass of oxygen = 0.l44g

Percentage of boron = \(\frac{\text { Mass of boron }}{\text { Mass of compound }} \times 100\)

⇒ \(=\frac{0.096 \mathrm{~g}}{0.240 \mathrm{~g}} \times 100=40 \%\)

Percentage of oxygen =\(\frac{\text { Mass of oxygen }}{\text { Mass of compound }} \times 100\)

⇒ \(\frac{0.144 \mathrm{~g}}{0.240 \mathrm{~g}} \times 100=60 \%\)

Alternative method

Percentage of oxygen = 100 – a percentage of boron

= 100-40=60%

Read and Learn More Class 9 Science Solutions

Question 2. Calculate the molecular masses of H₂, O₂, Cl₂, CO₂, CH₄, C₂H_6, C₂H₄, NH₃, CH₃OH
Answer:

1. The molecular mass of H₂ (hydrogen)

= Atomic mass of hydrogen × 2 =1 × 2 = 2 u

2. The molecular mass of O₂ (oxygen)

= Atomic mass of oxygen × 2 = 16 × 2 = 32 u

3. The molecular mass of Cl₂ (chlorine)

Atomic mass of chlorine × 2 = 35.5 × 2 = 71 u

4. The molecular mass of CO₂ (carbon dioxide)

= (Atomic mass of carbon x 1) + (Atomic mass of oxygen × 2)

= 12 × 1 + (16 × 2) = 12 + 32 = 44 u

5. The molecular mass of CH₄ (methane)

= (Atomic mass of carbon × 1) +(Atomic mass of hydrogen × 4) =12 × 1 +(1 × 4) =12 +4 = 16 u

6. The molecular mass of C₂H₆ (ethane)

= (Atomic mass of carbon × 2) + (Atomic mass of hydrogen × 6)

= (12 × 2)+ (1 × 6) = 24 + 6 =30 u

7. The molecular mass of C₂H₄ (ethene)

= (Atomic mass of carbon × 2) + (Atomic mass of hydrogen × 4)

= (12 × 2) + (1 × 4) = 24 + 4 = 28 u

8. The molecular mass of NH₃ (ammonia)

= (Atomic mass of nitrogen × 1) + (Atomic mass of hydrogen × 3)

= (14 × 1) + (1 × 3)

= 14 + 3 =17u

9. Molecular mass of CH₃OH (methanol or methyl alcohol) = (Atomic mass of carbon × 1) + (Atomic mass ,of hydrogen × 3) + (Atomic mass of oxygen × 1 ) + (Atomic mass of hydrogen × 1)

= (12 × 1) + (1 × 3) + (16 × 1) + (1 × 1)

= 12 + 3 + 16 + 1

= 32 u

Question 3. Write the formulae for the following and calculate the molecular mass for each one of them.

1. Caustic potash
2. Baking soda
3. Caustic soda
4. Common salt

Answer:

1. KOH

Molecular mass of KOH =39 +16 + 1= 36 u

2. NaHCO₃

Molecular mass of NaHCO₃ = 23+ 1+ 12+ 3 × 16

= 23 + 1 + 12+ 48

=84 u

3. CaCO₃

The molecular mass of CaCO₃

= 40 + 12 + 3 × 16=100 u

4. NaOH

Molecular mass of NaOH =23+16 + 1

=40u

5. C₂H₅OH

Molecular mass of C₃H₅OH or C₂H₆O =2 ×12 + 6 × 1 + 16

=24 + 6 + 16

=46 u

6. NaCl,

Molecular mass of NaCl = 23 + 35.5

= 58.5 u

Question 4. A metal weighing 6 g formed diatomic oxide upon heating in the presence of air. The oxide thus formed weighed 10 g. Write the chemical name of the compound.
Answer:

Suppose the metal is M. The oxide being diatomic, should have the formula as MO.

The amount of oxygen present in the oxide

= 10 -6 = 4g

∵ 32 g O₂ =1 mol

∴ 4 g O₂ =0.125 mol

The reaction for the formation of oxide can be written as

M + O₂ → MO

Upon balancing we get,

M + O₂ → 2MO

1 mole O₂ reacts with 2 moles of metal

∴ 0.125 mole O₂ reacts with 0.25 mole of metal

Hence, we get

0.25 mole of metal = 6 g

or1 mole of metal =24 g

Thus, the metal is magnesium and the oxide is

magnesium oxide (MgO).

Question 5. Find the number of atoms in 120 g of calcium and 120 g of iron. Which one has more atoms and how much is the difference?

[Atomic mass of Ca =40 u, Fe =56 u]

Answer:

Gram molecular mass of Ca = 40 g

∵ 40 g of Ca contains, several atoms

= 6.022 × 10²³

120 g of Ca contains, several atoms

⇒ \(=\frac{6.022 \times 10^{23}}{40} \times 120\)

= 18.066 × 1023

= 1.8066 × 1024 atoms

Again, the gram molecular mass of Fe = 56 g

∵ 56 g of Fe contains several atoms

= 6.022 x 10²³

∴ 120 g of Fe contains several atoms

⇒ \(=\frac{6.022 \times 10^{25}}{56} \times 120\)

= 12.904 x 10²³ = 1.2904 x 1024 atoms

Therefore, 120g of calcium has more number of atoms.

Difference = (1.8066 -1.2904) x 10²⁴

= 5.162 x 10²³ atoms

Question 6. A sample of ethane (C₂H₆) gas has the same mass as 1.5 x 10²⁰ molecules of methane (CH₄ ). How many C₂H₆ molecules does the sample of gas contain?
Answer:

∵ 6.022 x 10²³ molecules of methane have mass

= Gram molecular mass of methane (CH₄)

=12+ 4 × 1 = 16 g

∴ 1.5 x 10²⁰ molecules of methane have mass

⇒ \(=\frac{16 \times 1.5 \times 10^{20}}{6.022 \times 10^{23}}=3.98 \times 10^{-3} \mathrm{~g}\)

This is also the mass of ethane (C₂H₆).

Gram molecular mass of ethane (C₂H₆)

= 2 × 12+ 6 × 1 = 24 + 6

= 30 g As 30 g of ethane has several molecules

=6.022 × 10²³

Question 7. If 3.42 g of sucrose is dissolved in 18 g of water in a beaker, then what will be the number of oxygen atoms in the solution?
Answer:

Step 1 Molar mass of sucrose,

C₁₂H₂₂O₁₁ =12×12+ 1 × 22+ 16 ×11 = 342g/mol

∵ 342 g of sucrose = 1 mole sucrose

∴ 3.42 g ofsucrose \(=\frac{1 \times 3.42}{342}=0.01 \text { mole sucrose }\)

∵ 1 mole of sucrose (C₁₂H₂₂O₁₁) contains O-atoms

= 11× 6.022 × 10²³

∴ 0.01 mole of sucrose will contain O-atoms = 0.01× 11× 6.023×10²³ = 6.6253 × 10²²

Step 2 18 g water (H₂O) = 1 mole O-atoms = 6.022 × 10²³ O-atoms

Step 3 By adding the number of O-atoms present in 3.42 g sucrose and 18 g water, we get 6.022 × 10²³ +6.6253 × 10²²

= 10²²(60.22+ 6.6253)

= 66.844 × 10²²

= 6.68 × 10²² atoms

Question 8. When 3.0 g of carbon is burnt in 8.00 g of oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.0g of oxygen? Which law of chemical combination will govern your answer?
Answer:

First, we find the proportion of mass of carbon and oxygen in carbon dioxide.

In CO₂, C: O =12: 32 or 3: 8

In other words, we can say that

12.00 g carbon reacts with oxygen =32.00 g

∴ 3.00 g carbon will react with oxygen = 8 g

Therefore, 3.00 g of carbon will always react with 8.0g of oxygen to form 11 g of carbon dioxide, even if a large amount (50.00 g) of oxygen is present. This means when 3.00 g of carbon is burnt in 50.00 g of oxygen, only 8.00 g of oxygen will be used to produce.

11.00 g of carbon dioxide. The remaining 42.00 g of oxygen will remain as it is. This reaction will be governed by the law of constant proportions.

Question 9. Which has more number of atoms? 100 g of N₂ or 100 g of NH₃
Answer:

The molar mass of 1 mole of N₂ = 2 × 14= 28 g

∵ 28 g of N₂ has several molecules

=6.022 x 10²³

∴ 100 g of N₂ has several molecules

⇒ \(=\frac{6.022 \times 10^{23} \times 100}{28}=2.1 \times 10^{24}\)

Atoms in 100 g of N₂ = 2.1 x 10²⁴ × 2

= 4.2 × 10²⁴ atoms.

Similarly, the molar mass of 1 mole of

NH₃= 14 + 3X1 =17 g

∵ 17g NH₃ has number of molecules =6.022 × 10²³

∴ 100 g NH₃ has several molecules

⇒ \(=\frac{6.022 \times 10^{24} \times 100}{17}=3.54 \times 10^{24}\)

Atoms in 100 g of

NH₃ =3.54  × 10²⁴ × 4 = 1.416 x10²⁴

Thus, 100 g of NH₃ has more number of atoms.

Class 9 Science Chapter 3 Atoms And Molecules Short Answer Type Questions

Question 1.

1. State the law of constant proportion.
2. In a compound carbon and oxygen react in a ratio of 3:8 by mass to form carbon dioxide. What mass of oxygen is required to react completely with 9 g carbon?

Answer:

1. The law of constant proportion states that “a pure chemical compound always consists of the same elements that are combined in a fixed (or definite) proportion by mass”.
2. Carbon: oxygen (by mass) =3: 8 i.e. 3 g of carbon requires 8 g of oxygen to form carbon dioxide.

∴ 9 g of carbon requires (3 × 8) 24 g of oxygen to form carbon dioxide.

Question 2. State three points of differences between an atom and a molecule.
Answer:

Question 3. Calcium carbonate decomposes on heating to form calcium oxide and carbon dioxide. When 10 g of calcium carbonate is decomposed completely then 5.6 g of calcium oxide is formed. Calculate the mass of carbon dioxide formed. Which law of chemical combination will you use in solving this problem? State the law.
Answer:

The reaction occurs as follows:

According to the law of conservation of mass, Total mass of reactant(s) = Total mass of products(s)

⇒ 10 g = 5.6 g + Mass of CO₂

⇒ Mass of CO₂ =10 —5.6 =4.4g

This problem is solved using the law of conservation of mass according to which mass can neither be created nor be destroyed during a chemical reaction.

Question 4. Give the formulae of the compounds formed from the following sets of elements.

1. Calcium and fluorine 
2. Hydrogen and sulphur
3. Nitrogen and hydrogen
4. Carbon and chlorine

Answer:

Question 5. A vessel containing 28 g of carbon monoxide gas to which 16 g of oxygen gas is added and the mixture is left for a few hours. When checked there was only one kind of gas (carbon dioxide) in the vessel. What change would you observe in the overall mass of the content? Give a reason for your answer.
Answer:

Carbon monoxide (CO) reacts with oxygen (O₂) to form carbon dioxide (CO₂). There will not be any change in the overall mass of the content of the vessel as the mass of the product formed is equal to the mass of reactants.

i.e. Mass of CO₂ =Mass of CO + mass of O₂

= 28+16 = 44 g

The above observation is based on the law of conservation of mass.

Question 6. Write the Latin names of sodium and iron.
Answer:

Latin name ofsodium (Na) = Natrium

Latin name ofiron (Fe) =Ferrum.

Question 7. Which of the following symbols of elements are incorrect? Give their correct symbols.

1. Cobalt (CO)
2. Carbon (c)
3. Aluminium (AL)
4. Helium (He)

Answer:

1. CO is an incorrect symbol of cobalt. Its correct symbol is Co.
2. c is the incorrect symbol of carbon. Its correct symbol is C.
3. AL is an incorrect symbol of aluminium. Its correct symbol is Al.
4. For helium, He is the correct symbol.

Question 8.

1. What is the relative atomic mass of an element?
2. What is the average atomic mass of hydrogen?

Answer:

1. Relative atomic mass is defined as the number of times a given atom is heavier than 1 /12th of the mass of 1 atom of C-12.
2. The atomic mass of hydrogen is taken as lu whereas actually, it is 1.008 u.

Question 9. Define atomic mass unit. State how atoms exist.
Answer:

• The atomic mass unit (amu) is defined as the mass unit equal to exactly 1/12th of the mass of one atom of the C-12 isotope.
• Atoms may exist independently in a free state (For example., He, Ne and Ar) or in a combined state.
• The combined form of atoms may have similar kinds of atoms (H₂, N₂, O₂ etc.) or different kinds of atoms (H₂O, CO₂, H₂S etc).

Question 10. Classify each of the following based on their atomicity.

1. F2
2. NO₂
3. N₂O
4. C₂H₆
5. P₄
6. H₂O₂
7. P₄O₁₀
8. HCl
9. He
10. O₃
11. CH₄
12. Ag

Answer:

1. Monoatomic: Ag, He
2. Diatomic: HCl, F₂
3. Triatomic : NO₂, N₂O, O₃
4. Tetraatomic : P₄, H₂O₂
5. Polyatomic : C₂H₆, P₄O₁₀, CH₄

Question 11. How do molecules react?
Answer:

Molecules exist in the following two forms

1. Molecules of elements These are formed by the combination of two or more atoms of the same element, for example., O₂, H₂, P₄ etc.
2. Molecules of compounds These are formed by the combination of atoms of different elements. For example., NH₃, CO₂ etc.

Question 12. State the number of atoms present in each of the following chemical species.

1. CO^2-₃
2. PO^3-₄
3. P₂O₅
4. CO

Answer:

1. Number of atoms in CO^2-₃

= Number of C-atoms + Number of O-atoms

= 1 + 3 = 4

2. Number of atoms in PO^3-₄

= Number of P-atoms + Number of O-atoms

=1+4=5

3. Number of atoms in P₂O₅

= Number of P-atoms + Number of O-atoms

=2+5=7

4. Number of atoms in CO

= Number of C-atoms + Number of O-atoms =1+1=2

Question 13. Write the cations and anions present (if any) in the following compounds.

1. CH₃COONa
2. NaCl
3. H₂
4. NH₄NO₃

Answer:

Question 14. Give the names of any two elements present in the following compounds: Baking powder, common salt, sulphuric acid
Answer:

• Baking powder (NaHCO₃) Sodium, hydrogen, carbon and oxygen.
• Common salt (NaCl) Sodium and chlorine.
• Sulphuric acid (H₂SO₄) Sulphur, hydrogen and oxygen.

Question 15.

1. Give one word for the following:
   1. Positively charged ion
   2. A group of atoms carrying a charge
2. Mention any two important rules for writing a chemical formula.

Answer:

1. Cation
   1. Polyatomic ion
2. Two rules for writing a chemical formula are:
   1. When a compound consists of a metal and a non-metal, the symbol of the metal is written first and on the left whereas of non-metal on its right.
   2. The valencies or charges on the ions must be balanced in the chemical formula.

Question 16. Write the molecular formulae for the following compounds.

1. Copper (2) bromide
2. Aluminium (3) nitrate
3. Calcium (2) phosphate
4. Iron (3) sulphide

Answer:

Question 17.

1. An element X has a valency of 2. Write the chemical formula for
   1. Bromide of the element
   2. Oxide of the element.
2. Define the formula unit mass of a substance.

Answer:

1. Valency of X = 2

Valency of bromine =1

∴ The formula of compound

= XBr₂

2. Valency of X =2

Valency of oxygen = 2

∴ The formula of compound

= X₂O₂ or XO

Formula unit mass is the sum of atomic masses of all atoms present in a formula unit of a compound. It is calculated by adding the atomic masses of all the atoms present in one formula unit.

Question 18. Write the chemical formulae of the following compound, using the criss-cross method.

1. Magnesium bicarbonate
2. Barium nitrate
3. Answer:

Question 19. Find the ratio by mass of the combining elements in the following compounds.

1. CaCO₃
2. MgCl₂
3. H₂SO₄
4. C₂H₅OH

Answer:

CaCO₃ → Ca : C : O = 40 : 12 : 48

= 10: 3:12

MgCl₂ → Mg : Cl = 24 : 2 × 35.3 = 24 : 71

H₂SO₄ H : S : O = 2 × 1 : 32 : 4 × 16

= 2:32:64 = 1:16:32

C₂H₅OH → C : H : O = 2x 12 : 6x 1 : 16

= 24:6:16 =12:3:8

Question 20. Nitrogen and hydrogen atoms combine in a ratio of 14 : 3 by mass to form an ammonia molecule. Find the formula of the ammonia molecule by calculating the molar ratio. [Given atomic mass of N = 14 u and H = 1 u]
Answer:

Number of nitrogen atoms present in the molecule

⇒ \(=\frac{\text { Proportion by mass }}{\text { Atomic mass }}=\frac{14}{14}=1\)

Number of hydrogen atoms present in the molecule _ Proportion by mass Atomic mass

⇒ \(=\frac{\text { Proportion by mass }}{\text { Atomic mass }}\)

⇒ \(=\frac{3}{1}=3\)

This means many nitrogen and hydrogen atoms combined in ratio =1:3

Thus, the formula of a molecule of ammonia is NH3.

Question 21. Give the chemical formulae for the following compounds and compute the ratio by mass of the combining elements in each one of them.

1. Ammonia
2. Carbon monoxide
3. Hydrogen chloride
4. Aluminium fluoride

Answer:

Question 22. An element Y has a valency of 4, write the formula for its

1. Chloride Sol.
2. Nitrate
3. Chloride
4. Nitrate

Answer:

Question 23. Out of the following which has more atoms?

1. 50 g of Cu,
2. 50 g of Fe

[Atomic mass of Cu = 63.5 u, Fe =56 u]

Answer:

Number of atoms in 63.5 g Cu = 6.022 × 1023

Number of atoms in 1 g \(\mathrm{Cu}=\frac{6.022 \times 10^{23}}{63.5}\)

Number of atoms in 50g Cu

⇒ \(=\frac{6.022 \times 10^{23}}{63.5} \times 50\)

⇒ \(4.74 \times 10^{23} \text { atoms }\)

Number of atoms in 56 g Fe = 6.022 x 1023

Number of atoms in 1 g Fe \(=\frac{6.022 \times 10^{23}}{56}\)

Number of atoms in 50 g Fe \(=\frac{6.022 \times 10^{23}}{56} \times 50\)

⇒ \(=5.37 \times 10^{23} \text { atoms }\)

∴ 50 g of Fe has more number of atoms.

Question 24. A compound XH is formed by the combination of an element X with hydrogen. Find the valency of the element. State the formula of the compound formed by the combination of X with nitrogen and X with oxygen.
Answer:

In the compound XH, the valency of elements X is 1.

1. The valency of nitrogen is 3.

The valency of element X is 1.

∴ The formula of the compound = NX₃

2. The valency of oxygen is 2.

The valency of element X is 1.

∴ The formula of the compound = OX₂.

Question 25. During photosynthesis, a six-carbon atom molecule, glucose (C₆H₁₂O₆), is formed. Calculate its molecular mass.

[Atomic mass C = 12.0uH = 1.0u and O = 16.Ou]

Answer:

The molecular mass of glucose

= 6 × atomic mass of C+ 12 × atomic mass of H + 6 atomic mass of O

= 6 × 12 +12 × 1+6 × 16

= 72 + 12 + 96

=180 u

Question 26. 6 g of coke consisting of 100% carbon, is burnt in the air. Find the number of oxygen atoms consisting of the carbon dioxide gas thus formed.
Answer:

Each carbon atom combines with two oxygen atoms on combustion as follows:

6 g of coke consist \(\frac{6}{12} \times N_A\)

Hence, the number of oxygen atoms

⇒ \(=2 \times \frac{6}{12} \times N_A=N_A\)

⇒ \(\left(N_A=6.022 \times 10^{23} \text { atoms }\right)\)

Question 27. The mass of a single atom of M is 3.05x 10^-22g. What is its atomic mass? What would this element be? Check the periodic table for possible answers.
Answer:

1 mole = atomic mass of an element

= 6.022 x 10²³ atoms

∵ Mass of 1 atom = 3.05 x 10^-22 g

∴ Mass of 6.022 x 10²³ atoms

= 3.05 x 1(T22 x 6.022 x 10²³ =183.671g

This is nearly the atomic mass of tungsten (W^183.8).

Question 28. What are polyatomic ions? Give examples.
Answer:

A group of atoms carrying a charge and behaving like one entity is known as a polyatomic ion. For example., an oxygen atom and hydrogen atom combine to form a hydroxide ion (OH^–) and one C-atom and three O-atoms combine to form a carbonate ion (CO^2-₃).

Question 29. Give the names of the elements present in the following compounds.

1. Quicklime
2. Hydrogen bromide
3. Baking powder
4. Potassium sulphate

Answer:

1. Quicklime Calcium oxide — CaO Elements Calcium and oxygen
2. Hydrogen bromide — HBr Elements Hydrogen and bromine
3. Baking powder Sodium hydrogen carbonate — NaHCO₃ Elements Sodium, hydrogen, carbon and oxygen
4. Potassium sulphate — K₂SO₄ Elements Potassium, sulphur and oxygen.

Question 30. Write the molecular formulae of all the compounds that can be formed by the combination of the following ions.

Cu²⁺, Na⁺, Fe³⁺, Cl^–, SO^2-₄ , PO^3-₄

Answer:

Question 31. In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g of water and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass.

Sodium carbonate + Ethanoic acid → Sodium ethanoate + Carbon dioxide + Water

Answer:

Total mass of reactants = Mass of sodium carbonate + Mass of ethanoic acid = 5.3 + 6.0 = 11.3 g

Total mass of products =Mass of sodium ethanoate + Mass of carbon dioxide + Mass of water = 8.2 + 2.2 + 0.9 = 11.3 g

Since the sum of masses of reactants is equal to the sum of masses of products, therefore, the observation made is in agreement with the law of conservation of mass.

Question 32. Hydrogen and oxygen combine in a ratio of 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
Answer:

Since H and O combine in the ratio of 1: 8 by mass.

Therefore, \(\frac{\text { Mass of } \mathrm{H}}{\text { Mass of } \mathrm{O}}=\frac{1}{8}\)

Let the mass of oxygen required to react completely with 3 g of hydrogen gas be x.

⇒ \(\frac{3}{x}=\frac{1}{8}\)

or x = 24 g

Therefore, 24 g of oxygen is required to react with 3 g of hydrogen to form water.

Question 33. Why is it not possible to see an atom with the naked eye?
Answer:

• Atoms are very small, they are smaller than anything we can imagine. More than millions of atoms when stacked would make a layer barely as thick as a sheet of paper.
• These are very small in radii and measured in terms of nanometers (1nm =10^-9m). Hence, it is not possible to see an atom with the naked eye.

Question 34. Write down the formulae of

1. Sodium oxide
2. Aluminium chloride
3. Sodium sulphide
4. Magnesium hydroxide

Answer:

Sodium oxide

Question 35. What is meant by the term chemical formula?
Answer:

It is the shortest way to represent a compound with the help of symbols and valency (charge) of elements, for example., Element

Question 36. How many atoms are present in a

1. H₂S molecule and
2. PO^3-₄ ion?

Answer:

1. In H₂S molecule, three atoms
   1. [i.e. 2 atoms of H + 1 atom of S] are present.
2. InPO^3-₄ ion, five atoms
   1. [i.e. 1 atom of P + 4 atoms of O] are present.

Question 37. Calculate the formula unit masses of ZnO, Na₂O, K₂CO₃. [Given, atomic mass of Zn = 65 u, Na = 23u, K = 39u, C = 12u andO = 16u]
Answer:

Formula unit mass of ZnO (zinc oxide)

= 65 +16 =81 u

Formula unit mass of Na₂O(sodium oxide)

= (23 x 2) + (16 x 1) = 46 + 16 = 62 u

Formula unit mass of K₂CO₃ (potassium carbonate) = (39 x 2) + (12 x 1) + (16 x 3)

= 78+12 + 48 =138 u

Class 9 Science Chapter 3 Atoms And Molecules Very Short Answer Type Questions

Question 1. How did Berzelius assign symbols to the elements?
Answer:

Berzelius assigned symbols to the elements by taking the first one or two letters of the element’s name in English and in some cases the symbols have been taken from the names of elements in different languages such as Latin, German, Greek etc.

Question 2. Give an example of a triatomic molecule of an element.
Answer: Ozone (O₂)

Question 3. Which is octatonic, carbon or sulphur?
Answer: Sulphur (S₈)

Question 4. Write one example of each.

1. Tetra-atomic molecule
2. Diatomic molecule

Answer: Phosphorus (P₄)

Question 5. Is argon monoatomic or diatomic?
Answer: Argon is monoatomic because its atom can exist independently.

Question 6. Give the difference between a cation and an anion.
Answer:

Cation It is a positively charged ion.

For example., Na⁺, K⁺,Ca²⁺,Mg²⁺ etc.

Anion is a negatively charged ion.

For example., Cr^–, Br^–, F^–,O^2-, N^3- etc.

Question 7. What is the difference between a sodium atom and a sodium ion?
Answer:

Question 8. Define a polyatomic ion. Give one example of it.
Answer:

A group of atoms carrying charge in a single entity is called a polyatomic ion. For example., sulphate ion (SO^2-₄) has five atoms.

Question 9. Choose an ionic compound among S₈ , Cu(NO₃)₂ , P₄ , H₂ and O₂?
Answer: Cu(NO₃ )₂ is an ionic compound because it has Cu²⁺ and NO^–₃ ions.

Question 10. What is the molecular formula of aluminium hydroxide?
Answer:

Question 11. What is the chemical formula of ammonium phosphate?
Answer:

Question 12. Choose the correct formulae of sodium sulphide and sodium sulphite: NaS, Na₂SO₄, Na₂S or Na₂SO₃.
Answer: Sodium sulphide = Na₂S Sodium sulphite = Na₂SO₃

Question 13. An element Z has a valency of 3. What is the formula of the oxide of Z?
Answer:

Question 14. If an element X has its valency equal to 3, what will be its formula with carbonate ion?
Answer:

Question 15. Calculate the formula unit mass of Na₂CO₃. [Atomic mass of Na = 23 u, C = 12 u, 0= 16 u]
Answer: Na₂CO₃ =2 × 23+ 12 + 3 × 16=106 u

Question 16. Calculate the formula unit mass of NaHCO₃. [Atomic mass of Na =23 u, H =1 u, C =12 u, O = 16 u]
Answer:

NaHCO₃ – (Atomic mass of Na) + (Atomic mass of H) + (Atomic mass of C) + (3 × Atomic mass of O)

= (23 + 1 + 12 + 3 × 16)

= 84 u

Question 17. What is the mass of sodium in 58.5 g of NaCl?
Answer:

23g [∵ Mass of sodium = 58.5— mass of Cl =58.5-35.5 = 23]

Question 18. Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
Answer:

‘The relative number and kinds of atoms are constant in a given compound This postulate explains the law of definite proportions.

Question 19. Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?
Answer:

The postulate which is the result of the law of conservation of mass is “atoms are indivisible particles, which can neither be created nor be destroyed in a chemical reaction”.

Question 20. Define atomic mass unit.
Answer:

One atomic mass unit (u) is the mass unit equal to exactly 1/12th of the mass of one atom of the C-12 isotope.

Class 9 Science Chapter 1 Matter In Our Surroundings Long Answer Type Questions

Question 1. What are the differences between solid, liquid and gaseous states?
Answer:

Differences between solid, liquid and gaseous states are as follows

Question 2.

1. Explain the term density. Arrange different states of matter in increasing order of density.
2. Explain how ice floats on water.

Answer:

1. The mass per unit volume of a substance is called density. Density depends upon the volume of the substance. Substances with small intermolecular spaces have small volumes and high densities.
   1. The increasing order of intermolecular spaces between the different states of matter is solid < liquid < gas. Thus, the increasing order for their density would be gas <liquid<solid.
2. Ice is a solid, but it has a cage-like structure in which some spaces are present between the particles of water.
   1. These spaces are trapped by the air particles. These spaces are larger as compared to the spaces present between the particles of water.
   2. Thus, the volume of ice is greater than that of water. Hence, the density of ice is less than water and it floats on water.

Read and Learn More Class 9 Science Solutions

Question 3. Benzoic acid is used as a food preservative. The given graph shows the heating curve for benzoic acid. Study the graph and answer the following questions:

1. At what time does benzoic acid begin to
   1. Melt?
   2. Boil?
2. What is the melting point of benzoic acid?
3. What happens to the temperature while benzoic acid melts?
4. What is the physical state of benzoic acid during a time interval of 35-45 minutes?

Answer:

1. 1. Benzoic acid begins to melt at 20 min.
   2. Benzoic acid begins to boil at 52 min.
2. The melting point of benzoic acid is120°C.
3. The temperature remains constant atl20°C until all the benzoic acid has melted.
4. The physical state of benzoic acid is liquid during the time interval of 35-45 min.

Question 4.

1. What is matter? Write two properties of solids and two properties of liquids.
2. Give reasons for the following:
   1. Ice at 0°C appears colder in the mouth than water at 0°C.
   2. Doctors advise putting strips of wet cloth on the forehead of a person with having high temperature.

Answer:

1. Matter is a substance which has mass and occupies space.
   1. In solids, the force of attraction between particles is strongest and intermolecular space is much less.
   2. In liquids, the force of attraction is relatively less and intermolecular space is more in comparison to solids.
   1. As ice absorbs the latent heat of fusion too from the mouth so, it feels colder than the water at the same temperature, i.e. 0°C.
   2. As the temperature of the patient’s body is high, the water from the wet strips evaporates by absorbing the heat from the body. This lowers the body temperature of the patient. That is why, doctors advised putting strips of wet cloth on the forehead of a person suffering from high fever.

Question 5. The temperature-time graph given below shows the heating curve for pure wax.

From the graph, answer the following:

1. What is the physical state of the substance at points A, B, C, and D?
2. What is the melting point of the wax?
3. What is its boiling point?
4. Which portions of the graph indicate that a change of state is taking place?
5. Name the terms used for heat absorbed during the change of states involved in the above processes.

Answer:

1. At point A = Solid wax
   1. At point B=Solid as well as liquid wax (Melting continues)
   2. At point C=Liquid wax
   3. At point D = Liquid as well as vapour state (Boiling continues)
2. Melting point of wax = 15°C
3. Boiling point of wax = 110°C
4. Straight lines in the curve parallel to the time-axis (tf-axis) indicate the change of state. These portions are Ax to Bx (solid to liquid) and D₁ to D₂(liquid to vapour state).
5. During melting, at the melting point, the heat absorbed is called latent heat of fusion. During boiling, at boiling point, the heat absorbed is called latent heat of vapourisation.

Class 9 Science Chapter 1 Matter In Our Surroundings Short Answer Type Questions

Question 1. Which of the following matters? Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume.
Answer:

• Anything that occupies space and has mass is called matter. Matter can exist in three physical states, liquid and gas.
• Chair and almonds are solid states of matter. A cold drink is a liquid state of matter. Air and the smell of perfume are gaseous states of matter.

Question 2. Give reasons for the following observation. The smell of hot sizzling food reaches you several metres away, but to get the smell of cold food, you have to go close.
Answer:

• Particles of matter are continuously moving. They possess kinetic energy. As the temperature rises, particles move faster.
• The particles of the aroma of hot food mix with the particles of air and reach us several metres away, but to get an aroma or smell of cold food, we have to go close because the particles that carry the smell of cold food move slower as compared to particles that carry the smell of hot sizzling food.

Question 3. A diver can cut through water in a swimming pool. Which property of matter does this observation show?
Answer:

This observation shows that the particles of matter have spaces between them.

Question 4. What are the characteristics of the particles of matter?
Answer:

Characteristics of particles of matter are as follows :

1. They are very small in size.
2. They move faster in a gaseous state as compared to a solid or liquid state.
3. They diffuse faster at higher temperatures.

Question 5. The mass per unit volume of a substance is called density (Density = Mass/Volume). Arrange the following in the order of increasing density. Air, exhaust from chimneys, honey, water, chalk, cotton and iron.
Answer:

The increasing order of density is : Air < exhaust from chimneys < cotton < water <honey < chalk < iron

Question 6.

1. Tabulate the differences in the characteristics of states of matter.
2. Comment upon the following.

Rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.

Answer:

1. For differences Refer to the text on the gaseous state and effect of change of temperature on page 4.
2. Rigidity The property due to which an object retains its shape and size is known as rigidity. Solids are rigid while liquids and gases are not. Compressibility

The property due to which a substance is reduced to its lower volume when force is applied is called compressibility. Gases are the most compressible while solids and liquids are not.

• Fluidity The property due to which a substance tends to flow is known as fluidity. Gases and liquids can flow, hence they are known as fluids.
• Filling a gas container Particles of a gas move freely in all directions and occupy all the space available to them. Hence, gas fills the container.
• Shape The geometry of an object is called its shape. Solids have a definite shape while gases and liquids do not.
• Kinetic energy The energy of particles of matter due to their movement is called their kinetic energy.
• Gases have maximum kinetic energy among the three states of matter. Kinetic energy increases with the rise in temperature and vice-versa.

Density The mass per unit volume of a substance is called its density.

∴ \(\text { Density }=\frac{\text { Mass }}{\text { Volume }} \text { or } D=\frac{m}{V}\)

Generally, a substance has a maximum density in its solid state as compared to a liquid or gaseous state. Units of density are kg m-3 or g cm-3.

Question 7. Give reasons.

1. A gas fills the vessel in which it is kept.
2. A gas exerts pressure on the walls of the container.
3. A wooden table should be called a solid.
4. We can easily move our hands in the air but to do the same through a solid block of wood, we need a karate expert.

Answer:

1. Particles of gas have the least forces of attraction between them hence, they move freely in all directions and occupy all the space available to them. Hence, a gas fills the vessel in which it is kept.
2. Due to the high kinetic energy possessed by the gas particles, they randomly move at a high speed within the container.
   Due to this random movement, the particles hit each other as well as the walls of the container. The force by which these particles strike the container exerts pressure on its walls.
3. A wooden table has a definite shape and volume. It is very rigid and cannot be compressed. Wood has all the characteristics of a solid. Hence, a wooden table should be called a solid.
4. Particles of air are very far apart from each other due to negligible forces of attraction between them. Therefore, our hands get sufficient space to move in the air. We also displace the air particles without much effort.
   1. But in a solid block of wood, particles are closely packed with the least space between them due to strong intermolecular forces of attraction. So, there is no possibility of moving hands through a block of wood.

Question 8. Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.
Answer:

• The mass per unit volume of a substance is called density. As the volume of a substance increases, its density decreases.
• Though ice is solid, it has a cage-like structure in which some spaces are present between the particles of water (these spaces are left when water solidifies). These spaces are trapped by the air particles.
• In fact, these spaces are larger as compared to the spaces present between the particles of water. Thus, the volume of ice is greater than that of water.
• Hence, the density of ice is less than that of water. A substance with a lower density than water can float on water. Thus, ice floats on Water.

Question 9. Convert the following temperatures to Celsius scale.

1. 300 K
2. 573 K

Answer:

For converting Kelvin to Celsius, the formula is

K-273 = °C

1. 300K-273 =27°C
2. 573 K – 273 = 300°C

Question 10. What is the physical state of water at

1. 250°C?
2. 100°C?

Answer:

1. Water vapour or steam.
2. Liquid water as well as water vapour, as steam and water, co-exist atl00°C.

Question 11. For any substance, why does the temperature remain constant during the change of state?
Answer:

1. During the change of state, the temperature remains constant because the heat provided is utilised for breaking the attraction forces between the particles of the substance.
2. This happens at the melting point (or boiling point) of the substance and the heat used is called the latent heat of fusion (or vapourisation). During condensation or solidification, the vice-versa happens.

Question 12. Suggest a method to liquefy atmospheric gases.
Answer:

Applying high pressure and reducing temperature, helps to liquefy atmospheric (or any other) gases. Because under these conditions, the particles come closer, kinetic energy decreases and the gas is liquefied.

Question 13. Why does a desert cooler cool better on a hot dry day?
Answer:

• On a hot dry day, the temperature is high and the humidity is low. The rate of evaporation increases with an increase in temperature and a decrease in humidity. A desert cooler functions on the principle of evaporation.
• The water takes heat from the hot desert cooler and evaporates. The evaporation of water cools the pads and the circulating water. As a result, the incoming air also gets cooled down.

Question 14. How does the water kept in an earthen pot (matka) become cool during summer?
Answer:

• Earthen pots contain tiny pores. During summer, when water is poured into an earthen pot, some of the water seeps through pores to the outer surface.
• The water molecules on evaporation escape from the tiny pores of the earthen pot. The heat required for evaporation is taken from the earthen pot and the water in it.
• This results in a lowering of the heat content of the remaining water and the water becomes cool.

Question 15. Why does our palm feel cold when we put some acetone petrol or perfume on it?
Answer:

Acetone or petrol are volatile liquids which evaporate readily. When these liquids are kept on the palm, their particles gain energy from the palm or surroundings and evaporate, thus causing the palm to cool.

Question 16. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Answer:

A saucer or plate has more surface area in comparison to a cup. Therefore, the evaporation of tea occurs more in the saucer rather than cup and more cooling is observed in a saucer.

Question 17. What type of clothes should we wear in summer?
Answer:

We should wear cotton clothes in summer because cotton is a good absorber of water and helps in absorbing the sweat and exposing it to the atmosphere for easy evaporation thereby, causing a cooling sensation.

Question 18. Why is ice at 273 K more effective in cooling than water at the same temperature?
Answer:

When ice melts, it absorbs the energy equal to the latent heat of fusion from the surroundings so, it causes cooling more effectively than the water at the same temperature (because water does not absorb energy from the surroundings).

Question 19. What produces more severe burns, boiling water or steam?
Answer:

Steam causes more severe burns than boiling water. The reason is that it releases the extra amount of heat (latent heat) which it has already taken during vapourisation (when the steam was formed from water).

Question 20. Name A, B, C, D, E and F in the following diagram showing change in its state.

Answer:

A = Melting or fusion, here the solid changes into a liquid.

B = Evaporation or vapourisation, here the liquid changes into a gas.

C = Condensation or liquefication, here the gas changes into liquid.

D = Freezing or solidification, here the liquid changes into a solid.

E Sublimation, here solid directly changes into a gas without coming into a liquid state.

F-Sublimation, here gas changes into a solid without coming in a liquid state.

Question 21. Convert the following temperatures to the Celsius scale.

1. 293 K
2. 470 K

Answer:

1. 293 K- 273 =20°C
2. 470K-273 = 197°C

Question 22. Convert the following temperatures to the Kelvin scale.

1. 25°C
2. 373°C

Answer:

1. 23°C + 273 =298 K
2. 373°C + 273 = 646 K

Question 23. Give a reason for the following observations:

1. Naphthalene balls disappear with time without leaving any solid.
2. We can get the smell of perfume sitting several metres away.

Answer:

1. Naphthalene being a sublimable substance converts directly from a solid to a gaseous state by taking heat from the surroundings through the process, called sublimation.
   1. The naphthalene balls keep on forming naphthalene vapours which slowly disappear into the air. Hence, no residue is left after some time.
2. The smell or aroma of perfume reaches several metres away due to the fast diffusion of the gaseous particles of perfume through air.

Question 24. Arrange the following substances in increasing order of forces of attraction between the particles-water, sugar, and oxygen.
Answer: Oxygen (gas) < Water (liquid) < Sugar (solid).

Question 25. What is the physical state of water at

1. 25°C?
2. 0°C?
3. 100° C?

Answer:

1. Liquid state
2. Solid or liquid state (transition state)
3. Liquid or gaseous state

Question 26. Give two reasons to justify.

1. Water at room temperature is a liquid.
2. An iron almirah is solid at room temperature.

Answer:

1. Water is liquid at room temperature as
   1. It tends to flow.
   2. It takes the shape of the vessel in which it is filled, but its volume does not change.
2. An iron almirah is solid at room temperature because
   1. It has a definite shape and volume.
   2. It is hard and rigid.

Question 27. Carbon dioxide (CO2) is a gas. Justify the given statement by giving two reasons.
Answer:

The two reasons to justify that carbon dioxide is a gas are:

1. Carbon dioxide does not have a fixed volume. It can be compressed by applying pressure.
2. Carbon dioxide does not have a fixed shape. It can take the shape of the container in which it is filled.

Question 28. Give one similarity and one dissimilarity between a liquid and a gas.
Answer:

Similarity Both liquids and gases are fluids and take the shape of the container in which they are placed.

Dissimilarity A gas can be compressed easily whereas a liquid cannot. A small quantity of gas can fill an entire given container. Also large quantity of a gas can be contained in a small space. A given amount of a liquid has a fixed volume at a given temperature.

Question 29. How melting point of a substance indicate the strength of its forces of attraction?
Answer:

More stronger the force of attraction, the more energy is required to break these forces. Hence, the substance which has a higher melting point indicates that its particles are tightly held.

Question 30. The melting points of two solids X and Y are 300 K and 400 K, respectively. Which has more intermolecular forces?
Answer:

The melting point of a solid is an indication of the strength of intermolecular forces between the particles of the solid. It shows that the strength of forces would be maximum in Y and minimum in X.

Question 31. Interconversion of states of matter occurs at constant temperatures. Explain.
Answer:

During the interconversion of state from solid to liquid or from liquid to gas, the temperature remains constant till all the solid has melted or all the liquid has vapourised. The heat energy is used up to overcome the forces of attraction.

Question 32. It is not proper to regard the gaseous state of ammonia as vapours. Explain.
Answer:

The gaseous state of a substance can be regarded as vapours only in case, if it is a liquid or solid at room temperature. Since ammonia is a gas at room temperature, its gaseous state cannot be regarded as vapours.

Question 33.

1. The conversion of solid to vapours is called sublimation. Name the term used to denote the conversion of vapours to solids,
2. The conversion of a solid state to a liquid state is called fusion. What is meant by the latent heat of fusion?

Answer:

1. It is also known as sublimation.
2. The amount of heat energy required to change 1 kg of a solid into liquid at atmospheric pressure and at its melting point is known as the latent heat of fusion.

Question 34. Alka was making tea in a kettle. Suddenly she felt intense heat from the puff of steam gushing out of the spout of the kettle. She wondered whether the temperature of the steam was higher than that of the water boiling in the kettle. Comment.
Answer:

• The temperature of both boiling water and steam is 100°C, but steam gives out more energy (due to latent heat of vapourisation) in comparison to boiling water.
• It is because, when water changes into steam, it absorbs the latent heat of vapourisation, but when steam condenses to form water, an equal amount of latent heat is given out without changing the temperature.

Question 35. Which phenomenon occurs during the following changes?

1. Formation of clouds
2. Drying of wet clothes
3. Wax melts in the sun
4. The size of naphthalene balls decreases

Answer:

1. Condensation
2. Evaporation
3. Fusion
4. Sublimation

Question 36. How will you change water from a gaseous state to a liquid state? Suggest a simple activity.
Answer:

• Water can be changed from a gaseous state to a liquid state by passing the water vapour through a water condenser as used in the case of simple distillation.
• Activity Take ice-cold water in a glass. Observe the outer surface of the glass. You find small droplets of water on it.
• These water droplets are formed as a result of condensation of water vapour present in the air to form liquid water.

Question 37. How do changes in temperature and humidity affect the rate of evaporation?
Answer:

• The rate of evaporation increases by increasing the temperature of the liquid. When the temperature of a liquid is increased by heating, more particles of the liquid get enough kinetic energy to go into a vapour state. This increases the rate of evaporation.
• When the humidity of the air is low, then the rate of evaporation is high and water evaporates rapidly. When the humidity of air is high then the rate of evaporation is low and water evaporates very slowly.

Question 38. Osmosis is a special kind of diffusion. Comment.
Answer:

• Diffusion is the process in which molecules of a substance move from the place of (their) higher concentration to the place of (their) lower concentration.
• But during osmosis, the water (or solvent) molecules move from (their) lower concentration to the place of their higher concentration through a semipermeable membrane. Thus, osmosis is termed a special kind of diffusion.

Question 39. Why does honey diffuse in water at a slower rate than ink?
Answer:

The density of honey is greater than that of ink, thus, honey takes a longer time to spread and hence, honey diffuses at a slower rate than ink.

Question 40. The table below shows the melting and boiling points of four pure substances. Which substance is a liquid at room temperature and would rapidly evaporate if left exposed to the air?

Question 41.

1. A sponge can be compressed, yet it is solid. Explain.
2. Name the state of matter that has minimum space between particles.

Answer:

1. A sponge has minute holes, in which air is trapped, when we press it, the air is expelled out and we can compress it. Hence, a sponge can be compressed, instead of being a solid.
2. Solid state has minimum space between their particles.

Question 42. The cover plate is removed from the gas jars shown in the diagram. After several days, the colour of the gas is the same in both jars. Why does this happen? Explain.

Answer:

• Diffusion has occurred in the jars. Bromine molecules move from a region where they are of higher concentration to a region of lower concentration, i.e. they move in the above gas jar.
• Oxygen molecules move from a region where they are of higher concentration to a region of lower concentration, i.e. they move to the below gas jar.
• Diffusion continues until both gas jars have a uniform distribution of bromine and oxygen molecules.

Question 43. Classify the following into osmosis/ diffusion.

1. Swelling up of a raisin on keeping in water.
2. Spreading of virus on sneezing.
3. Earthworms die on coming in contact with common salt.
4. Shrinking of grapes kept in thick sugar syrup.
5. Preserving pickles in salt.
6. Spreading of smell of cake being baked throughout the house.
7. Aquatic animals use oxygen dissolved in water during respiration.

Answer:

Osmosis

1. Swelling up of a raisin on keeping in water.

3. Earthworms dying on coming in contact with common salt.

4. Shrinking of grapes kept in thick sugar syrup.

5. Preserve pickles in salt.

Diffusion

2. Spreading of virus on sneezing.

6. Spreading of the smell of cake being baked throughout the house.

7. Aquatic animals use oxygen dissolved in water during respiration.

Question 44.

1. Explain the interconversion of three states of matter in terms of the force of attraction and kinetic energy of the molecules.
2. Arrange the three states of matter in the increasing order of rate of diffusion and particle motion.

Answer:

1. During the interconversion of a solid into a liquid and liquid into a gas at an increasing temperature, the kinetic energy of the molecules increases and the force of attraction among molecules decreases and vice-versa.
   1. Rate of diffusion, Solid < liquid < gas
   2. Particles motion, Solid < liquid < gas.

Question 45. How do you differentiate between solids, liquids and gases based on their melting and boiling points?
Answer:

Solids have melting and boiling points above room temperature. Liquids have a melting point below room temperature and a boiling point above room temperature. Gases have both melting and boiling points below room temperature.

Question 46.

1. Dry ice is compressed under high pressure. What happens to it when the pressure is released?
2. Define
   1. Melting point
   2. Fusion.

Answer:

1. On releasing the pressure, dry ice sublimes to a vapour state without undergoing a liquid state.
   1. Melting point The definite temperature at which a solid starts melting is called the melting point of that solid, for example., the melting point of ice is 0°C or 273.16 K.
   2. Fusion The process of conversion of a solid into liquid state on heating is called fusion or melting.

Question 47. What is dry ice? How is it formed?
Answer:

• Dry ice is solid carbon dioxide which sublimes to form carbon dioxide gas without going into a liquid state. The term dry is used to denote sublimation.
• On sublimation, vapours of carbon dioxide create a foggy dense appearance denoted by the term ice. Hence, solid carbon dioxide is also termed dry ice.
• Dry ice is formed when gaseous carbon dioxide is compressed and stored under high pressure. On decreasing pressure to 1 atm, it again changes to the gaseous form without coming into a liquid state.

Question 48. Draw a well-labelled diagram showing the sublimation of ammonium chloride.
Answer:

Take some ammonium chloride in a China dish and place the China dish on a tripod stand. Cover the China dish with an inverted glass funnel.

• Sublimation of ammonium chloride Put a loose cotton plug in the upper open end of the funnel to prevent the ammonium chloride vapour from escaping into the atmosphere.
• The China dish is heated by using a burner. On heating, ammonium chloride changes into white vapours.
• These vapours rise up and get converted into solid ammonium chloride on coming in contact with the cold, inner walls of the funnel.

Question 49. From the graph given below:

1. Which region contains only solids?
2. Which region contains all liquids?
3. Which region shows latent heat of vapourisation?

Answer:

1. AB is the region that contains only solids.
2. The CD is the region that contains all liquids.
3. DE is the region that shows latent heat of vapourisation.

Question 50. Comment on the following statements:

1. Evaporation produces cooling.
2. The rate of evaporation of an aqueous solution decreases with an increase in humidity.
3. Sponge though compressible is a solid.

Answer:

1. Evaporation of liquid produces cooling because liquid takes away the heat from the surroundings, thereby producing a cooling effect.
2. If humidity is high, then air is already saturated with water vapour, i.e. it has a lot of water vapour. Therefore, it will not take more water vapour easily. Hence, the rate of evaporation decreases.
3. The sponge has minute holes in which air is trapped. The material is also not so rigid. On pressing this, air is expelled out, which is why, it can be compressed, but it is solid as it has a definite shape and volume and does not change its shape unless compressed.

Question 51.

1. How will you show that the process of evaporation depends on the nature of the liquid?
2. Why a drop of Dettol is evenly distributed in a bucket of water without the need to stir?

Answer:

1. Take 10 mL of ether (a low boiling point liquid with a boiling point of 34°C) in a test tube and 10 mL of water (boiling point 100°C) in another test tube. Keep both the test tubes near the window for some time. It is observed that ether evaporates in a shorter time. Thus, the lower the boiling point of the liquid, the higher is its rate of evaporation.
2. A drop of Dettol is diffused in water and can be distributed throughout the water since there is enough space between the particles of water.

Question 52. Look at the following figures and suggest in which of the vessels A, B, C or D, the rate of evaporation will be the highest. Explain.

Answer:

• The rate of evaporation will be highest in vessel C as the surface area exposed for evaporation is larger than B ( smaller size).
• The moving fan increases the wind speed which also increases the rate of evaporation. Although A and D are also equal in size to C, A is at a greater distance from the fan and D is covered with a lid.

Question 53.

1. Which factors determine the state of a substance?
2. Convert 30°C into Kelvin.
3. Water droplets are observed on the outer surface of a glass tumbler containing ice-cold water. Give reason.

Answer:

1. Temperature and pressure determine the state of a substance.
2. 30°C = 273 + 30 = 303 K
3. Water droplets are observed on the glass tumbler because water vapours present in the air get condensed on the cold surface of the glass which appears as water droplets.

Question 54. It is a hot summer day. Priyanshi and Ali are wearing cotton and nylon clothes, respectively. Who do you think would be more comfortable and why?
Answer:

• Priyanshi would be more comfortable. The reason is that cotton absorbs sweat from the body and provides a larger surface area for evaporation which causes more cooling effect.
• Nylon being a bad absorber of water does not absorb sweat. Thus, the sweat does not evaporate from the body and Ali would feel uncomfortable.

Question 55. Tarun got an invitation to attend a party. On coming to the place, he found that both his shirt and pants were wet. What step he would take to dry them quickly?
Answer:

Tarun can take the following steps to dry his clothes quickly:

1. By spreading them in the air under the sun so that the water may evaporate (increasing the surface area).
2. By spreading them under a fan in a room (increasing the wind speed).
3. By ironing the clothes (increasing the temperature).

Question 56. While heating ice in a beaker with a thermometer suspended in it, a student recorded the following observations.

Based on the above observations, answer the following questions:

1. State the change (s) observed between 2-3 min and name the process involved.
2. Between 30-35 min, the temperature remains constant. State the reason for this. Name the heat involved in the process and define it.

Answer:

1. Between 2-3 min, ice is converted into water and this process is called fusion.
2. Between 30-35 min, heat is used for converting water (liquid) to vapour (gas), so the temperature during this period remains constant. It is due to the latent heat of vapourisation.
   1. Latent heat of vapourisation The amount of energy required to change 1 kg of water to its vapours at its boiling point is known as the latent heat of vapourisation.

Question 57.

What temperature on the Kelvin scale is equal to 50°C?

Describe an activity to show that the rate of evaporation increases with surface area.

Answer:

1. 50+273= 323 K
2. Activity Take a small amount of water in three containers which have different surface areas. Keep them in sunlight for 2 h. Measure the volume of water left in all three containers. O
   1. Observation The amount of water left will be the least in a container having the largest surface area among them. Conclusion The Greater the surface area, more will be the rate of evaporation.

Class 9 Science Chapter 1 Matter In Our Surroundings Very Short Answer Type Questions

Question 1. A substance has no mass. Can we consider it a matter?
Answer: No, because matter has a definite mass.

Question 2. A given substance X has definite volume, but no definite shape and can diffuse easily. What is the physical state of a substance X?
Answer:

The physical state of a substance X is liquid because liquids do not have definite shapes, but have a definite volume and can diffuse easily.

Question 3. Rubber band changes its shape. Is it solid?
Answer:

Rubber band changes their shape under force and regain their shape after removing the force. Thus, it is a solid.

Question 4. Why do liquids take up the shape of the container in which they are kept?
Answer:

Forces of attraction are not very strong in liquids which is necessary to maintain their shape. Therefore, they acquire the shape of the container in which they are kept.

Question 5. Why do liquids have a mostly lower density than solids?
Answer:

Liquids have fewer forces of attraction (between their particles), hence less mass and more volume as compared to solids, thus they have less density than solids.

Question 6. What would be the effect of

1. Temperature and
2. The density of liquids on the rate of diffusion of liquids?

Answer:

1. On increasing temperature, the rate of diffusion of liquids increases.
2. The rate of diffusion is higher for a liquid having a lower density.

Question 7. Name the properties of gases that help aquatic plants and animals to survive in water.
Answer:

Diffusion, as oxygen diffuses in water, which aquatic plants and animals take in.

Question 8. Why a gas cylinder cannot be half-filled?
Answer:

Particles of gas move randomly at a very high speed and occupy all the space available to them at a very fast speed. Therefore, the gas cylinder cannot be half-filled according to the volume.

Question 9. Why do gases exert more pressure on the walls of the container than solids?
Answer:

In gases, the particles move randomly at high speed and they collide with each other and also with the walls of the container. Thus, they exert more pressure on the walls of the container than solids.

Question 10. Which characteristic of a gas is used in supplying oxygen cylinders to hospitals?
Answer:

Gases are highly compressible and can be liquefied. Due to these properties, gases are used in supplying oxygen cylinders to hospitals.

Question 11. What is the full form of CNG? Mention its one property which makes it so important.
Answer:

The full form of CNG is Compressed Natural Gas. It is a clean fuel which does not create pollution on combustion.

Question 12. Mention two ways to liquefy atmospheric gases.
Answer:

The two ways to liquefy atmospheric gases are:

1. Increasing pressure
2. Decreasing temperature

Question 13. At what temperature, do ice (solid) and water (liquid) co-exist together?
Answer:

At 0°C or 273 K (melting point of ice or freezing point of water), both ice (solid) and water (liquid) can co-exist.

Question 14. Why is boiling called a bulk phenomenon?
Answer:

Since, boiling starts from the bulk, i.e. inside the liquid, therefore it is a bulk phenomenon.

Question 15. Why does the temperature remain constant during sublimation?
Answer:

During the process of sublimation, heat given to the system is used to evaporate solid into vapour at constant temperature. B and C both are liquids at room temperature. However, B’s boiling point is quite close to the room temperature and it is therefore volatile.

Question 16. On suffering from fever which will lower your body temperature more, ice or ice cold water? Why?
Answer:

Ice will lower the body temperature more than ice-cold water because the latent heat of the fusion of ice is quite high (335 J/kg). Ice is, therefore, expected to absorb more heat energy from the body and will lower the body temperature more than ice-cold water.

Question 17. Water as ice has a cooling effect, whereas water as steam may cause severe burns. Explain these observations.
Answer:

When ice melts, it absorbs the energy equal to the latent heat of fusion from the surroundings, therefore, causing a cooling effect. But steam releases the extra heat (equal to the latent heat of vapourisation) which it has absorbed when water is converted into steam. So, steam produces severe burns.

Structure Of The Atom Multiple Choice Questions

Question 1. The cathode ray experiment was done for the first time by

1. Goldstein
2. J. J. Thomson
3. Dalton
4. Rutherford

Answer: 2. J. J. Thomson

J. J. Thomson, his first experiment was to build a cathode ray tube with a metal cylinder on the end.

Question 2. By whom was neutron discovered

1. J. Chadwick
2. Dalton
3. Bohr
4. Rutherford

Answer: 1. J. Chadwick

Neutron is another sub-atomic particle, discovered by J. Chadwick in 1932, It is represented by n. Neutrons are electrically neutral particles.

Question 3. ₁H¹ is named (termed) as

1. Protium
2. Deuterium
3. Tritium
4. Proton

Answer: 1. Protium

The name of the 1H1 is the protium.

Question 4. Which class is near the nucleus of the atom?

1. K-class (shell)
2. L-class (shell)
3. M-class (shell)
4. N-class (shell)

Answer: 1. K-class (shell)

K-class (shell) is the nearest the nucleus of the atom.

Question 5. How many neutrons are present in the nucleus of a hydrogen atom?

1. 1
2. 2
3. 3
4. 0

Answer: 4. 0

There are no neutrons in the nucleus of the hydrogen atom, hence mass number of hydrogen atoms is zero.

Question 6. Which one of the following elements has a 2, 8, 13, 1 electronic configuration?

1. Chromium
2. Copper
3. Silver
4. Palladium

Answer: 1. Chromium

The real electronic configuration of chromium is 2, 8, 13, 1 but according to Bohr, it’s 2, 8, 12, 2.

Question 7. The number of valence electrons present in Mg²⁺ ions is

1. 16
2. 8
3. 17
4. 18

Answer: 2. 8

Valency means several electrons are present in the outer shell.

For 12Mg(atom) =2, 8, 2, valence electrons = 7 But i2Mg+ 2 (ion) = 2, 8 valence electrons = 8

Question 8. Which of the following is the valency of an element, it has 2, 8, 2 electronic configurations.

1. 2
2. 4
3. 6
4. 0

Answer: 1. 2

The valency of an element is 2 because two electrons are present in the outer shell.

Question 9. Which one of the following is the electronic configuration of sodium?

1. 2, 8
2. 8, 2, 1
3. 2, 1, 8
4. 2, 8, 1

Answer: 4. 2, 8, 1

The atomic number of sodium is 11. So, electronic configuration ₁₁N = 2, 8,1.

Question 10. The isotope used in the treatment of goiter is

1. U-235
2. Iodine (I-131)
3. Co-60
4. Na-24

Answer: 2. Iodine (1-131)

An isotope of iodine (1-131) is used in the treatment of goiter.

Question 11. The nucleons are

1. Electrons are protons
2. Protons and neutrons
3. Electrons and neutrons
4. None of these

Answer: 2. Electrons are protons

Question 12. In Ruther Ford’s experiment a-particles were deflected because of

1. Electrostatic attraction between y particles and positively charged part of an atom
2. Electrostatic repulsion between particles and the positively charged part of an atom
3. Electrostatic repulsion between p-particles and positively charged part of an atom
4. None of these

Answer: 2. Electrostatic repulsion between particles and the positively charged part of an atom

Question 13. The properties of an atom depends on

1. Number of protons
2. Number of neutrons
3. Atomic mass
4. Electronic structure

Answer: 4. Electronic structure

Question 14. Which one of the following is free of charge?

1. Electron
2. Proton
3. Neutron
4. None of the above

Answer: 3. Neutron

Question 15. The atomic number of sodium is 11 and its mass number is 23. It has

1. 12 protons and 11 electrons
2. 11 neutrons and 12 protons
3. 11 electrons and 12 neutrons
4. 12 electrons and 11 neutrons

Answer: 3. 11 electrons and 12 neutrons

Question 16. The mass of the nucleus is

1. Number of protons in the nucleus
2. Number of neutrons in the nucleus
3. Number of nucleons in the nucleus
4. None of these

Answer: 3. Number of nucleons in the nucleus

Question 17. The isotope used to remove brain tumors and treatment of cancer is

1. U-235
2. iodine
3. Co-60
4. Na-24

Answer: 3. Co-60

Question 18. Among the following is an element of electronic configuration

1. 2, 8
2. 2, 6
3. 2, 8, 18
4. 2, 8, 1

Answer: 2. 2, 6

Question 19. 8016, 8017, and 8018 are known as

1. Equilibrium
2. Even factor
3. Isotope
4. None of these

Answer: 3. Isotope

Question 20. Which of the following has the largest (maximum) number of isotopes?

1. Polonium
2. Hydrogen
3. Uranium
4. Lead

Answer: 1. Polonium

Class 9 Science Chapter 5 The Fundamental Unit Of Life Long Answer Type Questions

Question 1. Describe an activity to demonstrate endosmosis and exosmosis. Draw the diagram also.
Answer:

Activity to show endosmosis and exosmosis Put dried raisins in plain water and leave them for some time. Then place them into a concentrated solution of salt.

Observation

1. When dried raisins are placed in plain water, raisins swell up due to the osmotic entry of water into raisins. Plain water is a hypotonic medium for raisins. Thus, endosmosis occurs.
2. When swollen raisins are transferred to a concentrated solution, raisins shrink. Concentrated solution is a hypertonic medium for swollen raisins.
   Thus, exosmosis occurs.

Read and Learn More Class 9 Science Solutions

Question 2. Explain the main functional regions of a cell with the help of a diagram.
Answer:

The plasma membrane, cytoplasm and nucleus are the three main functional regions of a cell.

1. Plasma membrane It is a thin, selectively permeable membrane, covering the cell and is made up of lipids and proteins.
2. Cytoplasm It is an aqueous material containing a variety of cell organelles along with non-living inclusions.
3. Nucleus It is the control centre of a cell. It contains the cell’s hereditary information (DNA).

Question 3. Given below statements have underlined words which may be incorrect. Rewrite these words and state one function for each of them other than those (if) given.

1. The fundamental organisational unit of life is an organ.
2. The cell wall is an active part of the cell and is selectively permeable.
3. The presence of plasma membrane enables the cells of plants and fungi to exist in hypotonic media without bursting.
4. The Golgi body functions both as a passageway for intracellular transport and as a manufacturing surface.
5. Leucoplasts contain carotenoids and their primary function is storage.

Answer:

1. Cells perform many important physiological functions in living organisms essential for life.
2. Plasma membrane It acts as a mechanical barrier, preventing the leakage of cellular contents to the outside.
3. Cell wall It helps in interaction among plant cells through cytoplasmic channels called plasmodesmata.
4. Endoplasmic reticulum It functions as a cytoplasmic framework providing a surface for some biochemical activities of the cell.
5. Chromoplasts impart colour to the parts of plants like flowers and fruits.

Question 4.

1. Draw a neat labelled diagram of an animal cell.
2. Name the structure, which helps in
   1. Energy production
   2. Exchange of materials between cytoplasm and nucleoplasm.
   3. Lipid synthesis

Answer:

1. For the diagram of an animal cell.
2. Mitochondria
3. Nuclear pore
4. Smooth endoplasmic reticulum

Question 5. Why are mitochondria called the powerhouse of the cell? Give three similarities and one difference between mitochondria and plastids.
Answer:

Mitochondria are often associated with cellular respiration and energy generation of the cell. The energy required for various chemical activities is released by the mitochondria in the form of ATP molecules. For this reason, mitochondria are known as the powerhouse of the cell.

Three similarities between mitochondria and plastids are as follows

1. Both have their own DNA and ribosomes.
2. External structures of mitochondria and plastids are similar.
3. Both have more than one membrane layer.

One major difference between mitochondria and plastids is that mitochondria are present in both plant and animal cells, whereas plastids are present only in plant cells.

Question 6. Write the main functions of at least ten cell components.
Answer:

1. Plasma membrane It acts as a semipermeable membrane and allows only selective substances to pass through it.
2. Chromosomes carry the hereditary characteristics of an organism from one generation to another.
3. Lysosomes Breakdown of unwanted macromolecules is the main function of these organelles.
4. Ribosomes These help in protein synthesis.
5. Nucleus Control centre of the cell. Contains cellular DNA (genetic information) in the form of genes.
6. Mitochondria The main function of mitochondria in aerobic cells is the production of energy by the synthesis of ATP.
7. Nucleolus Biosynthesis of ribosomal RNA (rRNA) and acts as a platform for protein synthesis.
8. Cell wall It provides protection and rigidity to the plant cell.
9. Chloroplasts These are the sites of photosynthesis within plant cells.
10. The endoplasmic reticulum Serves as a channel for the transport of materials.

Question 7. Grass looks green, papaya appears yellow. Which Cell organelle is responsible for this?
Answer:

• Plastids These are found in plant cells only. Plastids are the major cell organelles in plants. On the basis of pigments present in plastids, they are divided into two types; the colourless leucoplasts and the pigmented chromoplasts.
• The colourless leucoplasts store starch, oil and protein granules whereas the pigmented chroloplasts have different colours and can be of several types.
• The most important ones are those containing the pigment chlorophyll, known as chloroplasts, which is responsible for the preparation of food by photosynthesis.
• Other chromoplasts contain non-green pigments, which are responsible for the characteristic colours of fruits and flowers.

Question 8. How are the following related to each other?

1. Chromatin network and chromosomes
2. Chloroplast and chromosomes
3. Genes and DNA

Answer:

1. The cell contains nuclear material which can be seen as an entangled mass of thread-like structure when it is not dividing. The chromatin material gets organised into rod-like structures called chromosomes when the cell is about to divide.
2. Chloroplasts are green-coloured plastids which contain a green-coloured pigment called chlorophyll.
3. Genes are the functional segments of DNA (present on DNA) which control a specific trait by making specific proteins.

Class 9 Science Chapter 5 The Fundamental Unit Of Life Short Answer Type Questions

Question 1. A cell is a building block of an organism. Explain why.
Answer:

The body of an organism is made up of various organ systems and these organ systems are made up of various tissues and tissues are the groups of cells performing the same function. Hence, a cell is a building block of an organism.

Question 2. Every multicellular organism has arisen from a single cell. Justify this statement.
Answer:

Cells divide to produce cells similar to themselves. Thus, all cells are derived from pre-existing cells and every multicellular organism has arisen from a single cell, for example., the development of a human starts from a single diploid cell called a zygote formed by the fusion of an ovum and sperm.

Question 3. Illustrate the various functions performed by a cell.
Answer:

Cell performs various functions in our body such as

1. Synthesis of substances like proteins and lipids.
2. Secretion of enzymes.
3. Removal of dead materials.
4. Oxidation to generate energy.

Question 4. Describe the structural features of the cell membrane and cell wall. Why is a cell membrane called a selectively permeable membrane?
Answer:

• The cell membrane is a flexible, semipermeable and living portion of a cell, which is made up of lipids and proteins. On the other hand, a cell wall is a tough, rigid and non-living portion of a plant cell, which is made up of cellulose.
• The plasma or cell membrane permits the entry and exit of selected materials in and out of the cell. It also prevents the movement of cell content outside the cell. Hence, it is called a selectively permeable membrane.

Question 5. Explain in detail what you know about the structure of the nucleus.
Answer:

Robert Brown discovered the nucleus in the cell in 1831. The nucleus is the control centre of a cell.

The structure of the nucleus is composed of

1. The nuclear membrane encloses the nucleus in eukaryotes. The nuclear membrane is penetrated by large nuclear pore complexes, which selectively transport molecules into or out of the nucleus.
2. Nucleoplasm It is a kind of protoplasm found in the nucleus containing genetic material (DNA), chromosomes and nucleolus.
3. Chromatin The chromatin material inside the nucleus is an organisation of DNA and protein. As a cell prepares itself to divide, the chromatin condenses and becomes thick enough to form specialised structures called chromosomes.
4. Nucleolus It acts as the most important site of RNA synthesis. It was first recognised by Fontana in 1874.

Question 6.

1. Where are chromosomes located? What is chromatin material and how does it change just before the cell divides?
2. The functional segments of DNA are genes/ Give reason.

Answer:

1. Chromosomes are located in the nucleus of the cells. Chromatin is a mass of thread-like structures. It condenses to form chromosomes just before the cell divides.
2. Genes present in DNA segments carry the hereditary information in them, which is transferred from one generation to next. They determine the structural and functional aspects of the next generation.

Question 7. State some differences between cytoplasm and nucleoplasm.
Answer:

Differences between cytoplasm and nucleoplasm are as follows:

Question 8. Differentiate between diffusion and osmosis.
Answer:

Differences between diffusion and osmosis are as follows

Question 9. What do you mean by plasmolysis?
Answer:

When a living plant cell loses water through osmosis, shrinkage or contraction of the cell contents away from the cell wall occurs. This phenomenon is known as plasmolysis.

Question 10. What would happen, if a cell wall is not present in plant cells?
Answer:

1. The shape of a cell will not remain definite because the cell wall provides structural strength to plant cells.
2. The cell will not be able to withstand pressure and burst if placed in very dilute media.

Question 11. Differentiate between Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER). How endoplasmic reticulum is important for membrane biosynthesis?
Answer:

Differences between RER and SER are as follows:

Question 12. Differentiate between nucleus and nucleoid.
Answer:

Differences between nucleus and nucleoid are as follows:

Question 13. What does a chromosome contain?
Answer: Chromosomes contain genetic information to be transferred from one generation to the next generation in the form of DNA (Deoxyribonucleic Acid).

Question 14. Differentiate between Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER). How endoplasmic reticulum is important for membrane biosynthesis?
Answer:

Differences between RER and SER are as follows

Question 15. Describe the phenomenon of membrane biogenesis. Give one function of ER.
Answer:

• The smooth endoplasmic reticulum helps in the manufacture of lipid or fat molecules, important for cell function. Some of these lipids and proteins manufactured in RER help in building the cell membrane.
• This process is known as membrane biogenesis. ER functions as a cytoplasmic framework providing a surface for some of the biochemical activities of the cells.

Question 16. Name the organelle of the cell, which is involved in the formation of lysosomes. Write its functions in the cell.
Answer:

Golgi apparatus is the organelle involved in the formation of lysosomes.

The functions of the Golgi apparatus are

1. Storage, modification and packaging of products in vesicles.
2. Helps to make complex sugars from simple sugars.
3. Material synthesised near the ER is packaged and dispatched to various targets inside and outside the cell through the Golgi apparatus.

Question 17. Name two nucleic acids found in the cell. Write their functions.
Answer:

• DNA and RNA are two nucleic acids present in the nucleus of a cell.
• Functions DNA is responsible for the storage and transmission of hereditary information, while RNA helps in the synthesis of protein. RNA is the genetic material of some viruses.

Question 18. Categorise the cells on the basis of the presence or absence of a nuclear membrane.
Answer:

Cells, which have nuclear membranes are called eukaryotic cells. On the contrary, the cells without nuclear membrane are called prokaryotic cells.

Question 19. What are the different types of endoplasmic reticulum found in an eukaryotic organism? Also, write one major function of each.
Answer:

Question 20. Write two functions indicating that lysosomes are the suicidal bags of the cell.
Answer:

The following two functions show that lysosomes are the suicidal bags of the cell

1. Lysosomes are the waste disposal system of the cells. They help keep the cells clean by digesting cellular wastes generated in cell.
2. Lysosomes also aid in phagocytosis. They digest foreign material entering the cell and kill them.

Question 21. Give scientific reasons for the following

1. The inner membrane of mitochondria is deeply folded.
2. Mitochondria are able to make some of their proteins.

Answer:

1. The inner membrane of mitochondria is deeply folded as these folds create a large surface area for ATP-generating chemical reactions.
2. Mitochondria contain their own DNA and ribosomes and hence, can make their own proteins.

Question 22. Bacteria do not have chloroplast, but some bacteria are photoautotrophic in nature and perform photosynthesis. Which part of the bacterial cell performs this?
Answer:

Bacterial cell do not have chloroplast yet some photoautotrophic bacteria perform photosynthesis due to the presence of light-absorbing pigments and reaction centres embedded in the cell membrane. The reaction centres exist in forms of sacs, tubes or sheets depending on the amount of surface area needed.

Question 23. Name the two cell organelles, which are bound by a double-layered membrane. Give one function of each.
Answer: Mitochondria- site of ATP-generating reactions. Chloroplasts- site of photosynthesis.

Question 24. Give a one-word answer to the following:

1. Organelle containing chlorophyll.
2. An organelle with cristae.
3. An organelle with ribosomes attached to its surface.
4. Living matter of the cell.

Answer:

1. Chloroplast
2. Mitochondria
3. Rough endoplasmic reticulum
4. Protoplasm

Question 25. Why do some regions appear darker than other regions on staining the cell with methylene blue? Name the other solutions that can be used for staining.
Answer:

Different regions of cells get coloured differentially due to their chemical composition.
Other solutions that can be used for staining are iodine solution or safranin solution.

Question 26. How does a fungal cell differ from a bacterial cell?
Answer:

Differences between fungal cells and bacterial cells are as follows:

Question 27. Explain how do cell walls permit the cells of fungi to withstand very dilute external media without bursting.
Answer:

• Fungi withstand very dilute/hypotonic external media without bursting because of their cell walls.
• In such media, the cells swell up by taking up water through osmosis and hence, building up pressure against the cell wall. The wall exerts an equal pressure against the swollen cell, thus preventing it from bursting.

Question 28. Why does the skin of your fingers shrink when you wash clothes for a long time?
Answer:

• The solution of soaps and detergents is hypertonic as compared to the osmotic concentration of our skin.
• Therefore, washing clothes results in exosmosis in skin cells that come in contact with the soap solution. Due to this reason, the skin of the fingers shrinks while washing clothes for a long time.

Question 29. A person takes a concentrated solution of salt. After some time, he starts vomiting. What is the phenomenon responsible for such a situation? Explain.
Answer:

The solution of salt is hypertonic, so causes irritation and excessive dehydration due to exosmosis in the intestine. This makes the person uncomfortable causing reverse movements such as vomiting.

Question 30. If you are provided with some vegetables to cook, during the cooking process you generally add salt to vegetables. After adding salt, vegetables release water. Which mechanism is responsible for this?
Answer:

On adding salt to vegetables, they release water due to exosmosis. When the external medium is hypertonic as compared to the osmotic concentration inside living cells, exosmosis occurs.

Question 31. What happens to an animal cell when it is placed in a very dilute external medium? Explain. Can diffusion lead to the same consequences?
Answer:

• In such conditions, the animal cell will gain water and would swell up or may even burst.
  Due to endosmosis, water moves from the dilute external medium through the semipermeable cell membrane into the cell with low water concentration.
• No, diffusion can not lead to the same consequences. It causes equal distribution. So, there will be no swelling or shrinkage of the cell.

Question 32. Why is endocytosis found in animals only?
Answer:

• Endocytosis is the process of swallowing food and other substances from an external medium by a plasma membrane. This is possible only when the plasma membrane is in direct contact with the external medium.
• It occurs only in animal cells because they lack cell walls. Plant cells contain cell walls, due to which their plasma membrane fails to perform endocytosis.

Question 33. The Golgi apparatus is also called the secretory organelle of the cell’. Why?
Answer:

The Golgi apparatus is also called a secretory organelle because secretion is the main function of the Golgi apparatus. The secretory proteins and lipids are packed and released on the surface by Golgi via exocytosis.

Question 35.

1. Why lysosomes are known as ‘scavengers of the cell’?
2. Lysosomes are self-destructive. True/ false. Give reason.

Answer:

1. Lysosomes are called scavengers of the cell because they remove dead and worn-out cells by digesting them and act as a kind of waste disposal system of a cell.
2. Lysosomes are self-destructive. This is true as during the breakdown of cell structure, lysosomes may burst and the enzymes contained in it may eat up their own cells.

Question 36. How many membranes are present in mitochondria? Give the characteristic features of these membranes. What is the advantage of such features?
Answer:

Mitochondria have two membranes. The outer membrane is very porous, while the inner membrane is deeply folded. A porous membrane helps in getting oxygen and food, while the folds create a large surface area for ATP-generating chemical reactions.

Question 37. Name a cell organelle found only in a plant cell and mention its various types along with their functions and location.
Answer:

Plastids are found only in plant cells.

Types of plastids are as follows

Question 38. Which type of plastid stores starch, oil and proteins?
Answer:

Leucoplasts are the plastids that function to store starch, oil and proteins hence, it is three types

1. Amyloplasts – Store starch
2. Elaioplasts – Store oil
3. Aleuroplasts – Store proteins

Question 39. Why do plant cells possess large-sized vacuoles?
Answer:

Plant cell possesses large-sized vacuoles because

1. It stores salt, sugar, amino acid, organic acid and some proteins.
2. The vacuole contains cell sap and helps maintain the turgidity of a cell.
3. They store some metabolic byproducts or end products of plant metabolism.
4. lysosomal enzymes occur in the vacuole of plant cells.

Question 40. State the reason for the following

1. Mitochondria is known as the powerhouse of the cell.
2. Plant cell shrinks when kept in a hypertonic solution.

Answer:

1. Oxidation of food takes place in mitochondria, which results in the release of energy in the form of ATP. This energy helps in various chemical activities needed for life. Hence, mitochondria are known as the powerhouse of the cell.
2. A hypertonic solution has a lower concentration of water than the cell. When a plant cell is kept in it, water present in the cell leaves the cell due to exosmosis. Therefore, the cell shrinks.

Question 41. Name the organelles, which show analogy written as under.

1. Transporting channels of the cell.
2. Powerhouse of the cell.
3. Packaging and dispatching unit of the cell.
4. Digestive bag of cells.
5. Storage sac of the cell.
6. Control room of the cell.

Answer:

1. Endoplasmic reticulum
2. Mitochondria
3. Golgi apparatus
4. Lysosome
5. Vacuole
6. Nucleus

Question 42. Carry out the following osmosis experiment:

Take four peeled potato halves and scoop each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing water. Now,

Keep cup A empty

1. Put one teaspoon of sugar in cup B.
2. Put one teaspoon salt in cup C.
3. Put one teaspoon of sugar in the boiled potato cup D.
4. Keep them for two hours. Then observe the four potato cups and answer the following:
5. Explain, why water gathers in the hollowed portion of B and C.
6. Why is potato A necessary for the experiment?
7. Explain, why water does not gather in the hollowed-out portion of A and D.

Answer:

1. The water gathers in the hollowed portion of B and C due to the process of osmosis. The concentration of solute (sugar in cup B and salt in cup C) is higher inside the cup than in water.
2. Hence, water flows from a region of higher concentration to a region of lower concentration.
3. Potato A acts as a reference of control for the experiment, which helps in comparing results.
4. Water does not gather in the hollow portion of A and D for the following reasons:
   1. The hollow portion of potato A is empty and there is no concentration difference so, no osmosis occurs.
   2. The hollowed portion of potato D contains sugar, but the potato cup is boiled. Osmosis cannot occur as the semipermeable membrane is destroyed by boiling.

Question 43. Make a comparison and write down ways, in which plant cells are different from animal cells.
Answer:

Comparison of Plant Cells and Animal Cells:

Question 44. What would happen if the plasma membrane ruptures or breaks down?
Answer:

In case the plasma membrane ruptures or breaks down,

1. All the useful substances will move out of the cell because the membrane is selectively permeable.
2. The transportation of materials will be disturbed.
3. The cell will lose its normal shape.
4. This may lead ultimately to the death of the cell.

Question 45. What would happen to the life of a cell if there was no Golgi apparatus?
Answer:

Effects of the absence of Golgi apparatus on the life of a cell are as follows:

1. The packaging and dispatching of different types of proteins to various targets inside and outside the cell will be influenced.
2. The products of cells cannot be stored and modified later.
3. This will affect the lysosome’s formation. This will cause an accumulation of worn-out and dead cell organelles within the cell, which may cause cell death.

Question 46. Which organelle is known as the powerhouse of the cell? Why?
Answer:

• Mitochondria are called the powerhouse of the cell. It contains oxidative enzymes, which oxidise the food and convert it into the energy currency of the cell in the form of ATP (Adenosine Triphosphate).
• This energy is used by body for making new chemical compounds and for doing other work. This is the reason, mitochondria are called the powerhouse of the cell.

Question 47. Why is the cell called the structural and functional unit of life?
Answer:

All living organisms are made up of cells, which perform various functions essential for the survival of the organisms, for example., respiration, digestion, excretion etc. Thus, a cell is the functional unit of life.

In unicellular organisms, a single cell carries out all the functions, while in multicellular organisms, a group of cells carry out different functions. Thus, a cell is the structural and functional unit of all living organisms.

Question 48. How do substances like CO₂ and water move in and out of the cell? Discuss.
Answer:

• CO₂ and other gases move in and out of the cell by the process of diffusion. When the concentration of carbon dioxide is higher inside the cell than outside, CO₂ diffuses out of the cell.
• If the CO₂ concentration inside the cell is less, CO₂ moves inside the cell from outside. The water moves in and out of the cell by the process of osmosis.
• Osmosis is the diffusion of water from a region of its high concentration to a low concentration through a semipermeable membrane.

Class 9 Science Chapter 5 The Fundamental Unit Of Life Very Short Answer Type Questions

Question 1. Who coined the term ‘protoplasm’ for the fluid substance of the cell?
Answer: Purkinje in 1839 coined the term protoplasm’ for the fluid substance of the cell.

Question 2. Name two unicellular organisms.
Answer: Paramecium and Chlamydomonas are the two unicellular organisms.

Question 3. Name the smallest known cell.
Answer: Mycoplasma is the smallest known cell.

Question 4. Plant cells have large vacuoles each surrounded by a membrane. What is the name of this membrane?
Answer: The membrane that surrounds the vacuole is called tonoplast.

Question 5. Write an example of diffusion in a plant.
Answer: Excess of CO₂ is present in the air as compared to leaf so, due to the process of diffusion, plants take CO₂ from the atmosphere to carry out photosynthesis.

Question 6. Name the process in which diffusion takes place through a semipermeable membrane.
Answer: Osmosis takes place through a semipermeable membrane.

Question 7. During cooking, on adding salt to the vegetables, water is released. Name the mechanism involved.
Answer: Osmosis.

Question 8. What will happen if the already swollen raisin is kept in a salt solution?
Answer: The water flows out from the raisin and goes into the solution medium. Consequently, the raisin shrinks in size.

Question 9. Name the process by which unicellular freshwater organisms and most plant cells tend to gain water.
Answer: Endosmosis, i.e. inward movement of water into the cell from the surrounding medium.

Question 10. What is the function of cellulose in plant cells?
Answer: The plant cell wall is mainly composed of cellulose. Cellulose is a complex substance, which provides structural strength to plants.

Question 11. What does the nucleus contain?
Answer: The nucleus contains nucleolus and chromatin material.

Question 12. Why is the nucleus called the controller or brain of the cell?
Answer:

The nucleus coordinates and directs all the metabolic functions of the cell, which is why it is called the controller or brain of the cell.

Question 13. State two important functions of the nucleus of the cell.
Answer:

1. The nucleus is the control centre of a cell.
2. It consists of cells’ DNA (genetic information) in the form of genes to carry hereditary characteristics from one generation to another.

Question 14. What are chromosomes made up of?
Answer: Chromosomes are made up of DNA and proteins.

Question 15. What is DNA? Where is it present?
Answer: DNA is Deoxyribonucleic Acid. It is the genetic map of an organism, present in the nucleus.

Question 16. How DNA is present in a cell which is

1. Dividing?
2. Not dividing?

Answer:

1. Chromosomes
2. Part of chromatin material.

Question 17. Which organelle is called the factory of ribosomes?
Answer: Nucleolus is called the factory of ribosomes.

Question 18. Name two structures, which are found in plant cell, but not in animal cell.
Answer: Chloroplast and cell walls are found in plant cell, but not in animal cells.

Question 19. Give the name of a structure and its function, which is found only in animal cells, but not in plant cells.
Answer: Centrioles are present only in animal cells and help in cell division.

Question 20. Which of the following are present in animal cells? Chloroplast, nucleus, vacuoles, cell wall and mitochondria Nucleus, vacuoles and mitochondria are present in animal cells. What are dictyosomes?
Answer: In plants, Golgi bodies are called dictyosomes.

Question 21. Is there any animal cell that lacks lysosomes?
Answer: Mammalian RBCs (Red Blood Corpuscles) lack lysosomes.

Question 22. In which cell organelle, the complete breakdown of glucose in the presence of oxygen takes place?
Answer:

The complete breakdown of glucose in the presence of oxygen in a cell is called aerobic respiration. It takes place in mitochondria.

Question 23. Name the energy currency of the cell.
Answer: Adenosine Triphosphate (ATP) is considered by biologists to be the energy currency of cells.

Question 24. Where- does the ATP synthesis occur in mitochondria?
Answer: ATP synthesis occurs in folds of the inner membrane of mitochondria called cristae.

Question 25. Which is the most widely occurring plastid and where is it present?
Answer: The most widely occurring plastid is chloroplast. It is present in all green plants.

Question 26. Name the type of plastid that helps in the process of photosynthesis.
Answer: Chloroplast helps in the process of photosynthesis.

Question 27. Where stroma is present in a cell?
Answer: Stroma is present in the chloroplast of the cell.

Question 28. Which organelles are present only in plant cells and possess their own genome and ribosomes?
Answer: Plastids are found in plant cells only and contain DNA, RNA and ribosomes.

Question 29. Why plastids are called the ‘kitchens of the cell’?
Answer:

Because they contain pigments which can trap sun energy and convert it into chemical energy, i.e. food called glucose.

Question 30. Who discovered cells and how?
Answer:

Cells were discovered by Robert Hooke in 1665. He observed cells in a cork slice with the help of a primitive microscope. The cork slice resembled the structure of a honeycomb consisting of many small compartments or box-like structures. Hooke called these boxes as cells.

Question 31. Why is the plasma membrane called a selectively permeable membrane?
Answer:

The plasma membrane is called a selectively permeable membrane because it allows the entry and exit of some selected molecules only through the cells. It also prevents the movement of some other materials.

Question 32. How is a prokaryotic cell different from a eukaryotic cell? Or Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cells.
Answer:

Question 33. Can you name two organelles we have studied that contain their genetic material?
Answer: Mitochondria and plastids are the two cell organelles that contain their genetic material.

Question 34. If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen?
Answer:

Living cells are capable of performing certain basic functions due to the presence of cell organelles present in it. If these are destroyed then cells will not be able to work properly and will die after some time.

Question 35. Why are lysosomes known as suicidal bags?
Answer:

Lysosomes contain powerful digestive enzymes. During the disturbance in cellular metabolism, lysosomes may burst and digest their cell. Therefore, they are called suicidal bags of the cell.

Question 36. Where are proteins synthesised inside the cell?
Answer: Ribosomes are the site of protein synthesis inside the cell.

Question 37. Where do the lipids and proteins constituting the cell membrane get synthesised?
Answer:

The synthesis of lipids occurs in the Smooth Endoplasmic Reticulum (SER). The proteins are synthesised in the ribosomes, which are attached to the Rough Endoplasmic Reticulum (RER).

Question 38. How does Amoeba obtain its food?
Answer:

Amoeba obtains its food through endocytosis. It is the process of ingestion of food through the plasma membrane. This occurs due to the flexibility of the plasma membrane, which enables the Amoeba to engulf food and other materials from its surroundings.

Question 39. What is osmosis?
Answer:

Osmosis is a process of diffusion of water from a region of its higher concentration to a region of lower concentration through a semipermeable membrane.

The Fundamental Unit Of Life Multiple Choice Questions

Question 1. The word ‘cell’ is derived from

1. The Greek word that means ‘small box-like structure’
2. The Latin word that means a little room’
3. The Greek word that means a little room’
4. The Latin word that means ‘small box-like structure’

Answer: 2. The Latin word that means a little room’

Robert Hooke in 1665, while examining a thin slice of cork, discovered dead cells. He used the word’ cell, which is derived from Latin, and means a little room’ to describe these units of cork slice.

Question 2. Choose the incorrect statement from the following options.

1. All cells arise from pre-existing cells only
2. Rudolf Virchow proposed the cell theory
3. The nucleus was discovered by Robert Brown in 1831
4. The nucleus and cytoplasm of a living cell, all together form the protoplasm

Answer: 3. Nucleus was discovered by Robert Brown in 1831

• The nucleus was discovered by Robert Brown in 1831. The cell theory was proposed by
  Schleiden and Schwann in 1839, postulated that all living beings are composed of cells and their products.
• In 1855, Rudolf Virchow modified the cell theory with his postulate, ‘Omnis cellula-e-cellula, which means, a new cell is derived from a pre-existing cell only.

Question 3. Every living animal cell is enclosed by an outermost thin and delicate covering that separates the contents of the cell from the external environment, is primarily composed of

1. Glycolipids
2. Glycoproteins
3. Lipids
4. Phospholipids

Answer: 4. Phospholipids

• The outermost thin and delicate covering of animal cells that separates the contents of a cell from the external environment is called the plasma membrane or cell membrane.
• The chemical analysis of the plasma membrane revealed that it is primarily composed of phospholipids. While the remaining minor fraction is constituted by proteins embedded in the phospholipid layer, polysaccharides glycolipids, etc.

Question 4. While preparing a temporary mount of onion peel, the peel taken from the onion bulb is placed immediately into the Petri dish containing water, because

1. It is an experimental procedure
2. It brings out plasmolysis due to osmosis of water into the cell
3. It prevents the peel from getting folded and dehydrated
4. It removes the impurities from the peel

Answer: 3. It prevents the peel from getting folded and dehydrated

While preparing a temporary mount of plant cells or animal cells, the specimen collected is immediately placed into the Petri dish/watch glass containing water, to prevent the cells from dehydrating and the peel from getting folded.

Question 5. Which one of the following terms describes a nucleus without a nuclear membrane?

1. Nucleolus
2. Primitive nucleus
3. Nucleoid
4. All of these

Answer: 3. Nucleoid

The primitive type of undeveloped nucleus which lacks a nuclear membrane is called nucleoid. A nucleoid is found in prokaryotic cells, for example., bacteria.

Question 6. Which one of the following cellular functions is performed by the endoplasmic reticulum?

1. Production of hydrolytic enzymes
2. Supply of energy to the cell
3. Formation of lysosomes
4. Production of vacuoles

Answer: 1. Production of hydrolytic enzymes

The digestive or hydrolytic enzymes (proteins) are produced by the rough endoplasmic reticulum for the synthesis of lysosomes.

Question 7. The function of biosynthesis of the plasma membrane and metabolism of toxic or poisonous substances is carried out by

1. Rough endoplasmic reticulum
2. Golgi apparatus
3. Smooth endoplasmic reticulum
4. Both (1) and (3)

Answer: 3. Smooth endoplasmic reticulum

Smooth endoplasmic reticulum is involved in the detoxification of drugs, insecticides, etc., inside a cell. It also carries out the biogenesis of plasma membranes and various steroid hormones.

Question 8. Which one of the following is not a functional role of the plasma membrane?

1. It forms the microvilli in the intestines of human beings
2. It maintains the cellular homeostasis
3. It protects the cell from plasmolysis
4. It projects small finger-like projects called pseudopodia for endocytosis

Answer: 3. It protects the cell from plasmolysis

Plasmolysis is the phenomenon of contraction or shrinkage of protoplasm in a plant cell, away from the cell wall, due to exosmosis of water, when the cell is placed in a hypertonic solution.

The plasma membrane cannot restrict the osmosis of water, thus it cannot protect cells from plasmolysis.

Question 9. Choose the incorrect statement in context with the cell.

1. A cell can replicate independently to produce daughter cells
2. They can perform all the metabolic activities of an individual
3. Every organism starts its life as a single-cell
4. Mycoplasma is the smallest cell but is larger than bacterial cell

Answer: 4. Mycoplasma is the smallest cell, but is larger than bacterial cell

Mycoplasma (PPLO) is the smallest cell, which is smaller than bacteria, but larger than viruses.

Question 10. Select the correct functional role of the vacuole in a cell.

1. Vacuoles do not help in maintaining the rigidity of the cell
2. Vacuoles form thread-like tails in sperms of many mammals
3. Vacuoles expel excess water and waste products from the cell
4. Vacuoles store only excretory products of a cell

Answer: 3. Vacuoles expel excess water and waste products from the cell

In unicellular organisms, vacuoles carry out the role of expelling excess water and wastes from the cell. They also store food and water in cells and help maintain the rigidity of cells by controlling osmosis. Thus, they are also known as dustbins or storehouses of cells.

Question 11. Choose the incorrect statement

1. Lysosomes from the garbage disposal system of animal cells
2. Ribosome carries out the synthesis of proteins
3. Liquid content of the vacuole in a plant cell is called cell sap
4. The colorless plastid that stores proteins, lipids, and starch is named xanthophyll

Answer: 4. The colorless plastid that stores proteins, lipids, and starch is named xanthophyll

Leucoplast is a colorless plastid that stores proteins, lipids, and starch, while xanthophylls are yellow, red, or orange pigments of green plants.

Question 12. Who coined the term ‘protoplasm’?

1. Purkinje
2. Robert Brown
3. Virchow
4. Palate

Answer: 1. Purkinje

Question 13. The longest cell of the human body is

1. RBC
2. Nerve cell
3. Muscle cell
4. Sperm

Answer: 2. Nerve cell

Question 14. The outermost thin, living membrane that separates the contents of the cell from its external environment is called as

1. Slime layer
2. Cell wall
3. Cell membrane
4. Capsule

Answer: 3. Cell membrane

Question 15. Select the incorrect pair.

1. Powerhouse of cell—Mitochondria
2. Kitchen of cell—Chloroplast
3. Brain of cell—Ribosomes
4. Suicidal bag—Lysosomes

Answer: 3. Brain of cell—Ribosomes

Question 16. The example(s) of prokaryotic cells is/are

1. Blue-green algae
2. Fungi
3. Bacteria
4. Both (1) and (3)

Answer: 4. Both (1) and (3)

Question 17. Name the scientist who discovered the Golgi apparatus.

1. Camillo Golgi
2. Robert Brown
3. Leeuwenhoek
4. None of these

Answer: 1. Camillo Golgi

Question 18. Which of the following is/are semi-autonomous organelle(s)?

1. Nucleus
2. Mitochondria
3. Chloroplast
4. Both (2) and (3)

Answer: 4. Both (2) and (3)

Question 19. Which one of the following is known as the energy currency of the cell?

1. ATP
2. GTP
3. FTP
4. None of these

Answer: 1. ATP

Question 20. Oil or fat-storing plastids are called as

1. Elaioplast
2. Amyloplast
3. Aleuroplast
4. Tonoplast

Answer: 1. Elaioplast

Question 21. The function(s) of vacuoles is/are

1. To provide turgidity or rigidity to plant cell
2. Storage of food material
3. To expel excess of water
4. All of the above

Answer: 4. All of the above

Class 9 Science Chapter 6 Tissues Long Answer Type Questions

Question 1. Write a note on the protective tissue in plants. (Give appropriate diagram also)
Answer:

The protective tissue or the outermost covering of cells in plants is known as the epidermis, which performs a protective function (protecting plants from adverse conditions). It is usually made up of a single layer of cells. In dry habitats, the epidermis gets thicker to protect the plant from undue loss of water.

• On aerial parts of plants, epidermal cells often secrete a waxy, water-resistant layer on their outer surface. This waxy covering aids in protecting the plant against loss of water, mechanical injury, and invasion by parasitic fungi. The cells of epidermal tissue are present in a continuous layer without intercellular spaces.
• Small pores are present on the epidermis of the leaf. These pores are called stomata. They are enclosed by two kidney-shaped cells called guard cells. They help in gaseous exchange and transpiration.

Read and Learn More Class 9 Science Solutions

As the plant grows older, a strip of secondary meristem replaces the epidermis of the stem. This forms a several-layer thick cork or bark of the tree in which cells are dead and compactly arranged without intercellular spaces.

Question 2. List the characteristics of cork. How is it formed? Mention its role. NCERT Exemplar
Answer:

The common characteristics of a cork are as follows

1. It is the outer protective tissue of older stems and roots.
2. It is formed by a secondary lateral meristem called cork cambium.
3. The mature cork becomes dead and filled with tannin, resin, and air.
4. The cells are arranged compactly without intercellular spaces and several layers become thick, which are impermeable due to the deposition of suberin in their wall.

Formation of cork

As the plant grows older, the outer protective tissue undergoes certain changes. A strip of secondary meristem replaces the epidermis of the stem. Cells on the outside are cut off from this epidermal layer. This forms several layers of thick cork or bark with no intercellular spaces.

Role of cork

1. It prevents the loss of water by evaporation.
2. It protects plants from the invasion of parasites and other harmful microorganisms.

Question 3. The transportation system of plants is composed of complex permanent tissue. They have their transportation system within themselves. Justify in detail with appropriate diagrams.
Answer:

• The transportation system of plants is composed of complex permanent tissue. These tissues are made up of more than one type of cells, and all these cells coordinate to perform a common specific function.
• These cells may appear structurally different, but they perform the same function. The permanent tissues are of two types

Xylem It helps in the transportation of water and minerals from roots to other parts of the plant.

Elements Of Xylem

1. Tracheids and Vessels Tubular structure, transport water and minerals vertically.
2. Parenchyma Stores food and helps in the sideways conduction of water.
3. Fibers are Supportive in function.

The phloem transports food from leaves to other parts of the plant. Food is prepared in leaves by the process of photosynthesis.

Elements of phloem

1. Sieve tubes Tubular cells with perforated walls. These consist of living cells.
2. Companion cells Small elongated cells with dense cytoplasm.
3. Phloem parenchyma Thin-walled cells. Mainly function in storage and transportation of food.
4. Phloem fibers Thick-walled cells. These are dead cells. Provide mechanical strength to tissue.

Both the xylem and phloem maintain a transportation system within the plants. There is continuous transportation of food, water, and minerals within the plant.

This transportation is necessary for the proper growth and maintenance of the plant.

Question 4. How is adipose tissue different from blood tissue?
Answer:

Differences between adipose and blood tissue are as follows:

Question 5. Differentiate between bone and cartilage concerning structure, function, and location.
Answer:

Differences Between Bone And Cartilage Are As Follows

Question 6. Explain the significance of the following

1. Hair-like structures on epidermal cells.
2. The epidermis has a thick waxy coating of cutin in desert plants.
3. Small pores in the epidermis of the leaf.
4. Numerous layers of epidermis in cactus.
5. Presence of a chemical suberin in cork cells.

Answer:

1. They increase the total absorptive surface area and help in absorption.
2. Cutin has a waterproof quality and helps in preventing water loss due to transpiration. It also protects plants from entry of pathogens, etc.
3. They help in the gaseous exchange and transpiration process.
4. To prevent water loss.
5. Suberin makes cork cells impervious to gases and water.

Question 7. ‘We can control some of the actions of our body, but some are not in our control’. Comment on this statement,
Answer:

Some of the actions like moving our limbs, fingers, neck, etc., can be controlled by our will. We can move these parts of our body whenever we want to, but some actions of our body like contraction and relaxation of the heart, blinking of an eye, etc., are not under our will, i.e. we cannot stop the functioning of the heart if we want to do so. The actions, which can be manipulated by our wishes are known as voluntary actions.

The muscles, which can perform voluntary actions are voluntary.

• These muscles are also called skeletal muscles or striated muscles. Spindle-shaped muscle cells (al Striated muscle Cb) Smooth muscle These muscles are mostly attached to bones and help in body movement.
• Their cells are long, cylindrical, unbranched, and multinucleate (having many nuclei).
• The actions, which are not under our control are known as involuntary actions. These actions are performed by smooth muscles or involuntary muscles. Their cells are long with pointed ends (spindle-shaped) and uninucleate (single nucleus).

Question 8.

1. What will happen if cells are not properly organized in tissue?
2. Under certain circumstances, the squamous epithelium is known as stratified squamous epithelium. Justify.

Answer:

1. Different organisms whether unicellular or multicellular need to perform many functions in the body such as respiration, digestion, and locomotion.
   1. In multicellular organisms, cells present in a group and specialized in one particular function form a tissue.
   2. Some tissues help in growth, while others in locomotion and some in body movement.
   3. So, if cells are not organized in these tissues, then highly organized and specialized processes will become disorganized.
   4. There will be no coordination in the functioning of the cells and body.
2. When the simple squamous epithelium is arranged in a pattern of multilayers to prevent wear and tear, the epithelium is called the stratified squamous epithelium, for example., skin.

Class 9 Science Chapter 6 Tissues Short Answer Type Questions

Question 1. Explain the basic criteria for the classification of permanent tissue in plants.
Answer:

The following points form the basis of criteria for classification of permanent tissue in plants

1. Whether the tissue is made up of one type of cell (simple) or more than one type of cell (complex).
2. Function Supportive (parenchyma), protective (epidermis) or conducting (xylem and phloem).
3. Whether the cell wall is thick or thin.
4. Whether the cells are living or dead.

Question 2. List any six characteristics of parenchyma.
Answer:

The major characteristics of parenchyma are as follows

1. The cells of the parenchyma are living and possess the power of division.
2. Each parenchyma cell is isodiametric in shape with a thin cell wall and encloses dense cytoplasm and a small nucleus.
3. The cells are loosely packed with large intercellular spaces between them.
4. It is found in soft parts of plants such as the cortex of roots, ground tissue in the stem, and mesophyll cells of leaves.
5. It serves as a packing tissue to fill the spaces between other tissues and maintains the shape of a plant.
6. It stores waste products of plants such as tannin, gum, crystals, etc.

Question 3. Name the tissue responsible for the flexibility in plants. How would you differentiate it from other permanent tissues?
Answer:

Collenchyma tissue is responsible for providing flexibility in plants. Differences between collenchyma tissue and other permanent tissues (parenchyma and sclerenchyma) are as follows

Question 4.

1. Identify the given figures.
2. Give any two major differences between the structures identified.
3. Describe the role performed by these two in the plant body.

Answer:

1. The given figures are of tracheids
   1. And Vessels
   2. Of xylem tissue.
2. The differences between tracheids
   1. And Vessels
   2. Are as follows

Tracheids and vessels are lignified tissues that provide mechanical strength to the plant body. They also function in carrying water and mineral salts from roots to different parts of the plant body vertically.

Question 5. Describe three functions of protective tissue in plants.
Answer:

Two types of protective tissues present in plants are epidermis and cork. The three common functions of these protective tissues are as follows

1. Cork protects plants from invasion of parasitic microorganisms and excessive heat and cold.
2. The cuticle of the epidermis checks the excessive evaporation of water.
3. The epidermis allows transpiration and gaseous exchange through stomata.

Question 6. Give the name of the following

1. Tissue is concerned with the conduction of food materials.
2. Tissue capable of cell division.
3. Multiple pores are present in the epidermis of the leaf.

Answer:

1. Complex tissue (phloem)
2. Meristematic tissue
3. Stomata

Question 7. List the constituents of phloem. What will happen if the phloem at the base of a branch is removed?
Answer:

• Major constituents of phloem include sieve tubes, companion cells, phloem fibers, and phloem parenchyma.
• If the phloem at the base of the branch is removed, then a lower area of the branch will not receive food from the leaves. But the plant will not die, as it will continue to receive food from other branches as food can move through phloem in both directions.

Question 8. Which is the simplest protective tissue present in the animal body? State its two functions.
Answer:

The most simple protective tissue present in the animal body is epithelial tissue. Its major functions are as follows

1. It protects underlying cells from drying, injury, and infections.
2. It helps in the elimination of waste products from the body.

Question 9. Name the type of epithelium present in the respiratory tract. What is its specialization?
Answer:

The ciliated columnar epithelium is present in the respiratory tract of humans. It has specialized hair-like projections called cilia which help in the movement of substances and mucus forward. Thus, the name ciliated columnar epithelium.

Question 10. Give three differences between epithelial tissue and connective tissue.
Answer:

Differences Between Epithelial And Connective Tissues Are As Follows:

Question 11. Mention three different types of blood cells with their functions. Draw diagrams also.
Answer:

Three different types of blood cells are as follows

1. Red Blood Cells (RBCs) Contains hemoglobin, help in the transportation of gases, digested food, hormones, etc.
2. White Blood Cells (WBCs) Integral part of the immune system, that help in fighting diseases by producing antibodies and engulfing germs and pathogens.
3. Platelets Help in the clotting of blood.

Question 12. Differentiate between bone and cartilage.
Answer:

Differences Between Bone And Cartilage Are As Follows:

Question 13. Name the tissue that smoothens bone’s surfaces at joints. Describe its structure with the help of a diagram.
Answer:

Cartilage is the tissue that smoothens bone surfaces at joints. Structure It is a specialized connective tissue, which is compact and less vascular.

Its extensive matrix is composed of proteins and slightly hardened by calcium salts and also has a delicate network of collagen fibers, living cells, and chondrocytes. The chondrocytes are present in lacunae. Cartilage provides support and flexibility to body parts. It is present in the nose, trachea, ear, and larynx.

Question 14. Give the differences between tendon and ligament.
Answer:

The Differences Between Tendon And Ligament Are As Follows:

Question 15. State the functions of skeletal connective tissue.
Answer:

1. The functions of skeletal connective tissue are as follows
2. It gives a definite shape to the body.
3. It protects the vital organs of the body, for example., the brain.
4. It provides a surface for the attachment of muscles to increase their efficiency.

Question 16. Write a note about the structure and significance of striated muscles with a diagram.
Answer:

Striated muscles are voluntary muscles, i.e. we can move these muscles according to our will.

• These are mostly attached to bones and help in body movement. They show alternate light and dark bands or striations (when stained appropriately).
• Cells of striated muscles are long, cylindrical, unbranched, and multinucleate, for example., muscles of limbs.

Question 17. Name the kinds of muscles found in your limbs and lungs. How do they differ from each other structurally and functionally?
Answer:

1. Limbs Striated muscle.
   1. Structure Cells are long and cylindrical in shape, presence of dark and light bands, multinucleate and unbranched.
   2. Function Voluntary movement.
2. Lungs Smooth/non-striated muscle.
   1. Structure Cells are spindle-shaped, absent of striation, uninucleate, and unbranched. Function Involuntary movement.

Question 18. Which type of muscle, smooth or striated is found in the iris of eye? Why are smooth muscles called involuntary muscles? In what way are they different from striated muscles concerning several nuclei?
Answer:

Smooth muscles are found in the iris of the eye. Smooth muscles are the muscles that cannot be moved or stopped according to our will. So, they are known as involuntary muscles. Smooth muscles are uninucleate, whereas striated muscles are multinucleate.

Question 19. Draw a labeled diagram of unstriated muscle tissue and mention its occurrence, features, and functions.
Answer:

The diagram of unstriated muscle tissue is given

Occurrence These tissues are found in the walls of the alimentary canal, urinary bladder, esophagus, iris, bronchi, etc.

Features

1. They are unbranched and non-striated.
2. Cells are long, thin, and spindle-shaped.
3. Each cell has a single central nucleus.

Functions

1. These muscles do not work as per our will.
2. These carry out the movement in the urinary bladder and gall bladder.

Question 20. What are neurons? Where are they found in the body? What function do they perform in the body of an organism?
Answer:

Neurons are the structural and functional units of the nervous system. These are found in the brain, spinal cord, and nerves.

Functions

1. These coordinate various body parts during any body function.
2. These control all the activities of the body.
3. These transmit messages in the form of nerve impulses to the brain and spinal cord.

Question 21. Differentiate between axon and dendrite.
Answer:

Differences Between axons and dendrites are As Follows:

Question 22. Give one function of each of the following.

1. Stomata
2. Cardiac muscle fibres

Answer:

1. Stomata They help in the gaseous exchange between the plant and the atmosphere. Transpiration takes place through the stomata.
2. Cardiac muscle fibers They help in rhythmic contraction and relaxation of heart throughout the life.

Question 23. Write functions of the following

1. Areolar connective tissues
2. Neurons
3. Adipose connective tissues
4. Cardiac muscles

Answer:

1. Areolar connective tissues These fill the space inside the organs and support internal organs of the body. These also help in the repair of tissues.
2. Neurons These are the fundamental cells of nervous tissue. These are highly specialized for being stimulated and then transmitting the stimulus very rapidly from one place to another within the body.
3. Adipose connective tissues These are fat-storing tissue found below the skin between internal organs. The cells of this tissue are filled with fat globules. Due to the storage of fats, these act as an insulator.

Question 24. What happens, when

1. Formation of cork in older stems does not occur.
2. Blood platelets are removed from the blood.

Answer:

• If the formation of cork does not occur in older stems then the outer tissue will rupture due to the increase in girth and the plant will get infected by the parasites.
• Blood clotting will not occur at the site of injury. Bleeding will continue which may lead to death.

Question 25. How are simple tissues different from complex tissues in plants?
Answer:

The main points of difference between simple tissues and complex tissues are:

Question 26. Differentiate between parenchyma, collenchyma, and sclerenchyma based on their cell wall.
Answer:

Differences Between Parenchyma, Collenchyma, And Sclerenchyma Are As Follows:

Question 27. Give reasons for the following

1. Meristematic cells have prominent nuclei and dense cytoplasm, but they lack vacuole.
2. Intercellular spaces are absent in sclerenchymatous tissue.
3. We get a crunchy and granular feeling when we chew pear fruit.
4. Branches of trees move and bend freely in high wind velocity.
5. It is difficult to pull out a husk of coconut.

Answer:

1. Meristematic cells undergo division and do not store food, thus lacking vacuole.
2. Because their walls are lignified and form bundles for mechanical functions.
3. Due to the presence of sclerenchymatous tissue (stone cell) or sclereids, we get a crunchy feeling when we chew pear fruit.
4. The presence of collenchyma tissue provides flexibility to the branches of a tree.
5. The husk of coconut is made up of sclerenchymatous fibers, which are closely packed.

Question 28. What are the functions of the stomata?
Answer:

The main functions of stomata are:

1. They help in the exchange of gases with the atmosphere.
2. They help in the transpiration of water.

Question 29. Diagrammatically show the difference between the three types of muscle fibers.
Answer:

Question 30. Differentiate between striated, unstriated, and cardiac muscles based on their structure and site/location in the body.
Answer:

Question 31. Draw a labeled diagram of a neuron

Question 32. Name the following.

1. Tissue that forms the inner lining of the mouth.
2. Tissue that connects muscle to bone in humans.
3. Tissue that transports food in plants.
4. Tissue that stores fat in our body.
5. Connective tissue with a fluid matrix.
6. Tissue present in the brain.

Answer:

1. Squamous epithelium
2. Tendons
3. Phloem
4. Adipose tissue
5. Blood
6. Nervous tissue.

Question 33. Identify the type of tissue in the following: Skin, the bark of a tree, bone, the lining of the kidney tubule, and vascular bundle.
Answer:

• Skin Squamous epithelium
• The bark of tree Epidermal tissue
• Bone Connective tissue
• The lining of kidney tubule Cuboidal epithelium
• Vascular bundle Conductive tissue (xylem and phloem).

Question 34. What is the role of the epidermis in plants?
Answer:

Role of epidermis in plants:

1. It helps in the protection of the internal organs of plants.
2. It becomes thick and prevents water loss in plants living in very dry habitats.
3. Its cell secretes a waxy, water-resistant layer on the outer surface, which protects against loss of water, mechanical injury, and infections.
4. Leaf epidermis have stomata to help in gas exchange and transpiration.
5. In old plants, the epidermal layer becomes thick and forms cork. Cork cells contain a chemical called suberin in their walls, which makes them impervious to gases and water.

Question 35. How does the cork act as a protective tissue?
Answer:

Cork is made up of several layers of epidermal cells. These cells of cork are dead and compactly arranged without intercellular spaces. They also have a chemical called suberin in their walls, which makes cork impervious to gases and water.

Class 9 Science Chapter 6 Tissues Very Short Answer Type Questions

Question 1. Name the regions in which parenchyma tissue is present.
Answer:

Parenchyma tissue is mainly found in soft parts of the plant such as roots, stems, and leaves and is also present in ground tissue of petioles.

Question 2.

1. Which type of tissue is found at the shoot apex? Name another part of the plant body, where this type of tissue is found,
2. If a plant is to show longitudinal growth, which kind of meristematic tissue will be promoted in the plants?

Answer:

1. Apical meristem is found at the shoot apex. It is also present in the growing tips of roots.
2. Intercalary meristem helps in the longitudinal growth of plants.

Question 3. What is the specific function of cardiac muscle?
Answer: Cardiac muscles contract and relax rhythmically throughout life.

Question 4.

1. Identify the region of the stem marked A in the given diagram and the type of simple permanent tissue found in this region.
2. Mention any two characteristic features of this tissue.

Answer:

1. The region marked as A is the pith and the tissue is parenchyma.
   1. The cells of parenchyma are living, thin-walled and loosely packed.
   2. This tissue provides support to plants and also stores food.

Question 5.

1. Plant tissue is observed under a microscope, as shown in the given figure. Identify the tissue.
2. State the characteristic features of these cells.
3. Name any two parts of the plant, where such cells are present.

Answer:

1. It is parenchyma.
2. It consists of thin-walled unspecialized cells, which are loosely packed, i.e. having intercellular spaces. Each cell has a prominent nucleus.
   1. Pith
   2. Cortex

Question 6.

1. Identify the tissue given in the following figure.
2. Mention the characteristic features of the cells.
3. Specify the function of this tissue.
4. Name any one part of the plant, where these cells are present.

Answer:

1. The tissue given in the figure is collenchyma.
2. The cells of collenchyma are living, elongated, thickened at the corners, and have very little intercellular space.
3. It provides mechanical support and flexibility to the plant.
4. It is present in leafstalks, below the epidermis.

Question 7. What are the functions of collenchyma in plants?
Answer:

The functions of collenchyma are as follows

1. It allows easy bending in various parts of a plant (leaf and stem) without breaking them.
2. It also provides mechanical support to plants.

Question 8. Write the difference between aerenchyma and chlorenchyma.
Answer:

Differences between aerenchyma and chlorenchyma are as follows

Question 9.

1. Identify the tissue shown in the figure.
2. Specify any part of the plant, where such cells are present.

Answer:

1. Sclerenchyma
2. Sclerenchymatous cells are found
   1. Around vascular bundles
   2. In veins of leaves

Question 10. Write the functions of the following chemical substances found in plant tissues.

1. Lignin
2. Cutin

Answer:

1. The functions of lignin are as follows
   1. It is a chemical substance, which acts as cement and provides strength to the plant.
   2. The presence of lignin in plants makes the walls of sclerenchyma thick.
2. The functions of cutin are as follows
   1. It is a chemical substance having a waterproof quality, present in the epidermis of desert plants.
   2. It prevents excessive loss of water through transpiration.

Question 11. What is the difference between sclerenchyma and collenchyma?
Answer:

Differences Between Sclerenchyma And Collenchyma Are As Follows:

Question 12. Answer the following

1. How is the epidermis of the plants living in very dry habitats adapted?
2. Write functions of guard cells of stomata in the leaf.

Answer:

1. The epidermis of the plants living in very dry habitats has a thick waxy coating of waterproof cutin over it. This prevents the loss of water.
2. Guard cells help in exchange of gases with the atmosphere, due to the opening and closing of the stomatal pore.

Question 13.

1. Epidermal cells help in the absorption of water and nutrients from soil. How?
2. Write a note on a vascular bundle.

Answer:

1. Epidermal cells in roots bear long hair-like outgrowth, i.e. root hairs that greatly increase the total absorptive surface area and help in increased absorption of water and nutrients from soil.
2. The vascular bundle is formed of two main components known as xylem and phloem. Both of them are the conducting tissues that help in the conduction of water, minerals (xylem), and food (phloem) throughout the plant body.

Question 14. The diagram shows the part of a xylem vessel.

What is the function of the spiral structure X? What is it made up of?

Answer:

The spiral structure X is made up of lignified cellulose, which provides mechanical support to the xylem vessel.

Question 15. Give differences between sclerenchyma fibers and sclereids.
Answer:

The Differences Between Fibres And Sclereids Are As Follows:

Question 16. What is epithelial tissue? State the type of epithelial tissue present in the lining of blood vessels.
Answer:

The outermost covering or protective tissue in the animal body is called epithelial tissue. Simple squamous epithelium covers the lining of blood vessels.

Question 17. What is the function of areolar tissues?
Answer:

1. They act as supporting and packing tissue as they are found between visceral organs.
2. They help in the repair of tissue.

Question 18. Name the tissue present between internal organs. What are its functions?
Answer:

The tissue present between internal organs is areolar tissue.

Its functions are as follows

1. To provide support to internal organs.
2. To repair body tissue.

Question 19.

1. What will happen if the ligament gets overstretched?
2. Why are skeletal muscles known as striated muscles?

Answer:

1. Overstretching of ligament leads to sprain.
2. Skeletal muscles are known as striated muscles because they show dark and light bands or stripes or striation.

Question 20. Determine the location of the following tissues:

1. Unstriated muscle fibers
2. Cuboidal epithelium
3. Adipose tissue
4. Striated muscle fibers

Answer:

1. Alimentary canal, iris of the eye, ureter, bronchi, etc.
2. Kidney tubules and ducts of salivary glands.
3. Below the skin and between internal organs.
4. Limbs, tongue, etc.

Question 21. Cutting of rose plants is done timely in gardens, but still, it regains its length. Give reason.
Answer:

The rose plant regains its length because of the presence of intercalary meristem at the base of leaves or internodes on twigs. The cells of these tissues divide and increase the length of the plant.

Question 22. Do the roots of a plant continue growing after their tips are removed? Explain giving reasons.
Answer:

• No, roots do not grow after the removal of their tips. Normally, the apical meristem is present at the tip of the root, which divides repeatedly to increase its length.
• When tips are removed, the apical meristem is also removed and no further growth in the length of roots occurs.

Question 23. Water hyacinth floats on the water’s surface. Explain.
Answer:

Aerenchyma (a type of parenchyma) is present in water hyacinth, which encloses a lot of air and makes the plant lighter than water so that it can float on the surface of the water.

Question 24. A mango tree has several branches. Which tissue helps in the sideways conduction of water in the branches?
Answer:

Xylem vessels are very long tube-like structures formed by a row of cells placed end to end. The transverse walls between these cells are partially or completely dissolved to form continuous water channels. Thus, xylem vessels help in the sideways conduction of water.

Question 25. It is known that the function of the heart is to pump blood throughout the body. Can you explain the cause of this peculiar ability of the heart?
Answer:

The heart is made up of cardiac muscles. These cardiac muscles are involuntary muscles (not under the control of our will). These muscles show continuous rhythmic contraction and relaxation throughout life thereby, helping the heart to pump blood in our body.

Question 26. What is a tissue?
Answer: The group of cells combined together to perform a common function is called a tissue, for example., blood, and muscle.

Question 27. What is the utility of tissue in multicellular organisms?
Answer: The human body works with the principle of division of labor. The cells specializing in one function are grouped to perform a common function.

Question 28. Name the types of simple tissue.
Answer: The three main types of simple tissues are:

1. Parenchyma
2. Collenchyma
3. Sclerenchyma.

Question 29. Where is apical meristem found?
Answer: Apical meristem is present in the growing tips of stems and roots of plants.

Question 30. Which tissue makes up the husk of coconut?
Answer: Sclerenchymatous tissue.

Question 31. What are the constituents of phloem?
Answer: The main constituents of phloem are:

1. Sieve tubes
2. Companion cells
3. Phloem parenchyma
4. Phloem fibers.

Question 32. Name the tissue responsible for movement in our body.
Answer: Muscular tissue.

Question 33. What does a neuron look like?
Answer:

A neuron possesses a cell body and various processes emerging from it. These processes include a long axon and short dendrites.

Question 34. Give three features of cardiac muscles.
Answer: Features of cardiac muscles are listed below:

1. These are involuntary muscles.
2. Cardiac muscle cells are cylindrical, branched, and uninucleated.
3. These muscles show rhythmic contraction and relaxation throughout life.

Question 35. What are the functions of areolar tissue?
Answer: Functions of areolar tissue are as follows:

1. Areolar tissue fills the space inside the organs and supports them.
2. It helps in the repair of the tissue.

Question 36. How many types of elements together make up the xylem tissue? Name them.
Answer:

Four elements make up xylem tissue which include:

1. Tracheids
2. Vessels
3. Xylem parenchyma
4. Xylem fibers.