Chapter 1: Matter in Our Surroundings Long Questions | science Class 9 CBSE

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Chapter 1: Matter in Our Surroundings Long Questions | science Class 9 CBSE | ByteNotes.in

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Question 1

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Q1. Explain the physical nature of matter with suitable activities.

• Matter is made up of particles.
• These particles are very small and beyond imagination.
• Activity with salt and water shows particles mix and spread evenly.
• Potassium permanganate experiment proves the minuteness of particles.
• Even after several dilutions, the color is visible, indicating many particles.
• The diffusion experiment shows particles of matter occupy space.
• Thus, matter is particulate, not continuous.

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Question 2

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Q2. What are the characteristics of particles of matter?

• Particles of matter have space between them.
• They are continuously moving.
• They attract each other.
• The interparticle space allows mixing of substances.
• Movement causes diffusion, observed in gas and liquids.
• The force of attraction varies between solids, liquids, and gases.
• This explains rigidity, compressibility, and other properties.

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Question 3

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Q3. Describe the three states of matter and their properties.

• The three states of matter are solid, liquid, and gas.
• Solids have definite shape, fixed volume, and are rigid.
• Liquids have fixed volume but no fixed shape, and they flow.
• Gases have neither fixed shape nor volume and are highly compressible.
• Particle arrangement differs in each state.
• Solids have the least kinetic energy; gases have the most.
• Intermolecular force is strongest in solids, weakest in gases.

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Q4. How do solids, liquids, and gases differ in compressibility and rigidity?

• Solids are rigid and not compressible due to tightly packed particles.
• Liquids are less rigid and slightly compressible.
• Gases are highly compressible because of the large space between particles.
• The interparticle force in solids is strongest, giving rigidity.
• Gases exert pressure due to their random fast movement.
• Liquids show intermediate behavior between solids and gases.
• These properties define their practical usage (e.g., LPG cylinders).

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Question 5

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Q5. Explain how matter changes state with the help of temperature.

• Heat increases the kinetic energy of particles.
• Solid turns to liquid at melting point by overcoming attraction.
• Melting point of ice is 273.15 K (0°C).
• Further heating turns liquid into gas at boiling point (373 K for water).
• The state change occurs without temperature change during phase transitions.
• Latent heat is the energy absorbed without rise in temperature.
• The energy helps particles break free from attraction.

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Question 6

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Q6. Define latent heat of fusion and vaporisation with examples.

• Latent heat is the heat energy absorbed or released during change of state.
• Latent heat of fusion is required to convert 1 kg of solid to liquid at melting point.
• For example, ice absorbs latent heat to turn into water at 0°C.
• Latent heat of vaporisation is needed to convert 1 kg of liquid to gas at boiling point.
• Water absorbs this heat to become steam at 100°C.
• Steam has more energy than boiling water at same temperature.
• These processes show energy absorption without temperature change.

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Question 7

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Q7. What is sublimation? Give examples and explain with an activity.

• Sublimation is the change of solid directly into gas without becoming liquid.
• Camphor and ammonium chloride show sublimation.
• Activity with camphor under funnel demonstrates the process.
• On heating, camphor changes into vapour and deposits on funnel walls.
• Reverse of sublimation is deposition (gas to solid).
• Sublimation is a physical change seen in specific substances.
• No liquid phase is observed in this transition.

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Question 8

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Q8. How does change in pressure affect the state of matter?

• Increasing pressure can compress gases into liquids.
• Gases like CO₂ turn into solid under high pressure (dry ice).
• Pressure brings particles closer, overcoming separation.
• Cooling along with pressure enhances liquefaction.
• LPG and CNG are stored under high pressure.
• Decrease in pressure allows gas to expand and change state.
• Thus, pressure influences interconversion of matter.

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Question 9

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Q9. Explain the interconversion of three states of matter with a diagram.

• Solid to liquid: Melting or fusion.
• Liquid to gas: Vaporisation or boiling.
• Gas to liquid: Condensation.
• Liquid to solid: Freezing.
• Solid to gas: Sublimation.
• Gas to solid: Deposition.
• These processes depend on temperature and pressure.

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Question 10

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Q10. Describe evaporation and the factors affecting its rate.

• Evaporation is the conversion of liquid into vapour below boiling point.
• It occurs at the surface of the liquid.
• Factors: surface area, temperature, wind speed, humidity.
• Higher surface area increases evaporation.
• Higher temperature provides more kinetic energy.
• Lower humidity increases rate of evaporation.
• Wind carries away vapour, enhancing evaporation.

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Chapter sections

Chapter 1: Matter in Our Surroundings | Long Questions

Q1. Explain the physical nature of matter with suitable activities.

Q2. What are the characteristics of particles of matter?

Q3. Describe the three states of matter and their properties.

Q4. How do solids, liquids, and gases differ in compressibility and rigidity?

Q5. Explain how matter changes state with the help of temperature.

Q6. Define latent heat of fusion and vaporisation with examples.

Q7. What is sublimation? Give examples and explain with an activity.

Q8. How does change in pressure affect the state of matter?

Q9. Explain the interconversion of three states of matter with a diagram.

Q10. Describe evaporation and the factors affecting its rate.

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