Science Class 6 Important Questions Chapter 8 Curiosity

A Journey through States of Water

Fill in the Blanks:

1. Water can exist in three states: solid, liquid, and _______.
   • Answer: gas
2. The process of water changing into vapour is called _______.
   • Answer: evaporation
3. When water vapour cools and changes back into liquid, it is called _______.
   • Answer: condensation
4. Ice melts and changes into water when _______ is applied.
   • Answer: heat
5. Water droplets form on the outside of a cold glass due to _______ of water vapour in the air.
   • Answer: condensation
6. The continuous movement of water on, above, and below the Earth’s surface is known as the _______.
   • Answer: water cycle
7. Evaporation happens faster on a _______ day compared to a cold day.
   • Answer: hot
8. The process of changing liquid water into solid ice is called _______.
   • Answer: freezing
9. _______ is a process where water vapour in the air condenses to form clouds and falls back as rain.
   • Answer: Precipitation
10. The cooling effect of evaporation is caused by the absorption of _______ from the surroundings.
    • Answer: heat

True or False:

1. Water can exist in only two states: liquid and gas.
   • Answer: False (It can exist in three states: solid, liquid, and gas)
2. The process of evaporation happens only when water is boiled.
   • Answer: False (Evaporation occurs even at room temperature)
3. Water droplets on the outside of a cold glass are formed by evaporation.
   • Answer: False (They are formed by condensation)
4. The water cycle is the process of water moving through evaporation, condensation, and precipitation.
   • Answer: True
5. Water evaporates faster on a windy day than on a calm day.
   • Answer: True
6. Condensation is the process of turning liquid water into water vapour.
   • Answer: False (Condensation is the process of turning vapour into liquid)
7. Clouds are formed when water vapour in the air cools and condenses into tiny droplets.
   • Answer: True
8. Freezing is the process of turning water vapour into liquid water.
   • Answer: False (Freezing is the process of turning liquid into solid)
9. Evaporation causes a cooling effect because it releases heat into the surroundings.
   • Answer: False (It absorbs heat from the surroundings)
10. Rain is a result of condensation of water vapour in the air.
    • Answer: True

Question / Answer

1. What are the three states of water? Explain with examples.

Answer: The three states of water are:

• • Solid: Ice (e.g., frozen water in a freezer).
  • Liquid: Water (e.g., water in a river or glass).
  • Gas: Water vapour (e.g., steam from boiling water).

2. What is evaporation? Give two examples.

Answer: Evaporation is the process of water turning into water vapour. It occurs even at room temperature.

• Examples:
  • Clothes drying in the sun.
  • Water puddles disappearing after rain.

3. How is condensation different from evaporation?

Answer:

• • Evaporation is the process of liquid water turning into vapour.
  • Condensation is the process of water vapour turning back into liquid when it touches a cold surface.

4. Why do water droplets form on the outer surface of a glass filled with cold water?

Answer: Water droplets form on the outer surface of a cold glass due to  condensation. Water vapour in the air comes into contact with the cold surface of the glass, turning into liquid droplets.

5. What is the water cycle? Describe its key stages.

Answer: The water cycle is the continuous movement of water on Earth through different states.

• • Evaporation: Water from oceans and lakes turns into vapour.
  • Condensation: Vapour rises, cools, and forms clouds.
  • Precipitation: Water falls back to Earth as rain, snow, or hail.
  • Collection: Water collects in rivers, lakes, and oceans, continuing the cycle.

6. What factors affect the rate of evaporation?

Answer: Factors affecting evaporation include:

• • Surface area: More exposed surface area increases evaporation (e.g., water in a plate evaporates faster than in a cup).
  • Temperature: Water evaporates faster at higher temperatures.
  • Air movement: Wind increases evaporation by carrying away water vapour.

7. How does water change from solid to liquid and from liquid to gas?

Answer:

• • Melting: Ice (solid) turns into water (liquid) when heated.
  • Evaporation: Water (liquid) turns into vapour (gas) when heated further.

8. What is the role of condensation in the formation of clouds?

Answer: When water vapour rises and cools in the atmosphere, it condenses around dust particles to form tiny droplets. These droplets cluster together to form clouds.

9. Explain how evaporation causes a cooling effect.

Answer: Evaporation absorbs heat from the surroundings, which causes a cooling effect. For example, when water evaporates from the surface of the skin (sweat), it cools the body.

10. Why does water evaporate faster on a hot, windy day compared to a cool, calm day?

Answer:

• Heat increases the energy of water molecules, making them evaporate faster.
• Wind helps remove the water vapour from the surface, speeding up the process of evaporation.

11. What is freezing? Give an example.

Answer: Freezing is the process by which liquid water turns into solid ice when cooled.

• Example: Water turning into ice in a freezer.

12. What happens when water vapour comes in contact with a cold surface?

Answer: When water vapour touches a cold surface, it undergoes  condensation  and turns into liquid water droplets.

13. How do clouds form and what causes rain?

Answer: Clouds form when water vapour in the air condenses into tiny droplets. When these droplets combine and become heavy, they fall as  rain.

14. Why do we feel cooler when we sit under a fan after sweating?

Answer: The fan helps evaporate sweat faster, and the process of evaporation absorbs heat from the skin, creating a cooling effect.

15. How does the process of evaporation help in keeping water cool in an earthen pot (matka)?

Answer: In an earthen pot, water seeps through the porous surface and evaporates. The heat required for evaporation is drawn from the remaining water, cooling it.