Important Question Matter in Our Surroundings Chapter 1 Science Class 9 CBSE Board

Important Questions For All Chapters – Science Class 9

Short Questions

1. What is matter?
Ans:- Anything that occupies space and has mass is called matter.

2. Name the three states of matter.
Ans:- Solid, liquid, and gas.

3. What is diffusion?
Ans:- The intermixing of particles of two different types of matter on their own is called diffusion.

4. What is the melting point of ice?
Ans:- The melting point of ice is 273 K (0°C).

5. Define latent heat of fusion.
Ans:- It is the amount of heat required to change 1 kg of a solid into liquid at its melting point.

6. What is sublimation?
Ans:- The change of a solid directly into a gas without changing into liquid is called sublimation.

7. What is evaporation?
Ans:- The process by which a liquid changes into vapour at any temperature below its boiling point.

8. Which factor increases the rate of evaporation?
Ans:- Increase in surface area, temperature, and wind speed increases evaporation.

9. Why does a sponge get compressed easily?
Ans:- A sponge has air trapped in its pores, which can be expelled on pressing.

10. What is the SI unit of temperature?
Ans:- The SI unit of temperature is Kelvin (K).

Long Questions

1. Describe the characteristics of particles of matter.

Ans:-

• Particles of matter have space between them.
• They are continuously moving.
• They attract each other with a certain force that varies from one kind of matter to another.

2. Explain the three states of matter with examples.
Ans:-

• Solid: Definite shape, volume, and high rigidity. Example: Wood, ice.
• Liquid: Definite volume but no fixed shape. Example: Water, milk.
• Gas: Neither fixed shape nor fixed volume and are highly compressible. Example: Air, oxygen.

3. What happens when a solid is heated? Explain using ice as an example.
Ans:- When a solid like ice is heated, particles gain kinetic energy and start vibrating faster. The forces of attraction weaken, and at 273 K, ice melts into water. The temperature remains constant during this change as the heat is used as latent heat of fusion.

4. Define latent heat of vaporisation. How is it different from latent heat of fusion?
Ans:- Latent heat of vaporisation is the heat required to change 1 kg of a liquid into vapour at its boiling point.
Difference: Fusion changes solid to liquid, while vaporisation changes liquid to gas.

5. Explain the effect of temperature and pressure on the state of matter.
Ans:-

• Temperature: Increasing temperature increases particle motion and changes solid → liquid → gas.
• Pressure: Increasing pressure brings particles closer, converting gas → liquid or liquid → solid.

6. What factors affect the rate of evaporation?
Ans:-

• Surface area: Larger area → faster evaporation.
• Temperature: Higher temperature → faster evaporation.
• Humidity: More humidity → slower evaporation.
• Wind speed: Higher wind speed → faster evaporation.

7. Why does evaporation cause cooling? Give examples.
Ans:- During evaporation, particles absorb energy from surroundings to change into vapour, causing cooling.

Example:

• Sweat cools our body.
• Acetone on the palm feels cold.
• Water sprinkled on the roof cools it.

8. Explain how the smell of hot food reaches you faster than that of cold food.
Ans:- Particles of matter are always moving. At higher temperature, they move faster. So, hot food’s vapour particles diffuse more rapidly than cold food, allowing smell to reach faster.

9. Differentiate between solids, liquids, and gases based on shape, compressibility, and diffusion.

Ans:-

10. What is condensation and deposition? Explain with examples.
Ans:- 

• Condensation: The process of gas changing into liquid, e.g., water vapour forming droplets on a cold glass.
• Deposition: The direct change from gas to solid, e.g., frost forming from water vapour on cold surfaces.