Answers to the Questions from “A Journey Through States of Water”
1. Which of the following best describes condensation?
(iv) The conversion of water vapour into its liquid state.
2. Identify in which of the given processes evaporation is very important.
- (i) Colouring with:
- (b) Water colours
Evaporation helps water colours dry on the paper.
- (b) Water colours
- (ii) Writing on paper with:
- (b) Ink pen
Evaporation dries the ink, making the writing permanent.
- (b) Ink pen
3. Why does space around natural grass feel cooler than space around plastic grass?
Natural grass contains water that evaporates when heated, absorbing heat from the surroundings. This process cools the area. Plastic grass does not have water, so it does not provide this cooling effect.
4. Give examples of liquids other than water which evaporate.
- Alcohol
- Nail polish remover (acetone)
- Petrol
- Perfume
- Ether
5. Why does a fan help to dry wet clothes when evaporation needs heat, not cold air?
A fan speeds up air circulation, which removes the moist air near the clothes, allowing more water molecules to evaporate. The heat required for evaporation is taken from the environment or the clothes themselves, not from the fan’s air.
6. How does leaving sludge to dry before transporting reduce costs and enhance safety?
- Cost Efficiency: By drying, the weight of the sludge reduces significantly, decreasing transportation costs.
- Safety: Drying minimizes the risk of leaks and spills during transport, reducing environmental contamination and health hazards for handlers.
7. Observe the activities in your house for a day. Identify the activities that involve evaporation. How does understanding evaporation help in daily activities?
Activities involving evaporation:
- Drying wet clothes.
- Boiling water for cooking.
- Sweating to cool the body.
- Mopping floors.
- Using hand sanitizer.
Understanding evaporation helps us:
- Use fans to dry clothes faster.
- Realize the importance of hydration to combat sweat loss.
- Conserve energy by choosing the right conditions (like sunlight) for drying.
8. How is water present in the solid state in nature?
- Icebergs in oceans.
- Glaciers in mountains.
- Snowfall in colder regions.
- Frost on surfaces during winter.
9. Reflect on the statement: “Water is our responsibility before it is our right.” Share your thoughts.
Water is a finite and essential resource. While every individual has a right to access clean water, it is also our responsibility to conserve it for future generations. Avoiding wastage, protecting water bodies from pollution, and ensuring equitable distribution are key to fulfilling this duty.
10. How can you cool the seat of a two-wheeler parked on a sunny day?
- Pour a small amount of water on the seat. As the water evaporates, it will absorb heat, cooling the seat.
- Cover the seat with a wet cloth for a few minutes before sitting.
Learning Activities:
- Why does blowing air on a wet hand feel cooler than on a dry hand?
The water on the wet hand evaporates, taking heat from the skin. This cooling effect is absent on the dry hand. - Game Idea:
Create a board game where players answer questions on evaporation, condensation, and the water cycle to move forward. Challenge cards can simulate real-life scenarios like drying clothes or conserving water. - Role-Playing Activity:
Enact the water cycle stages in a school assembly. Assign roles for evaporation (sun), condensation (clouds), and precipitation (rain).
Would you like help designing these activities or expanding on the concepts further? 😊
Answers to the Questions from “A Journey through States of Water”
1. What is the process of converting water into its vapour state called?
The process is called evaporation.
2. What is the process of converting water vapour into its liquid state called?
The process is called condensation.
3. What are the different states of water?
Water exists in three states:
- Solid (ice)
- Liquid (water)
- Gas (water vapour)
4. What causes water to change its state?
Water changes its state due to heating or cooling.
- Heating converts ice into water (melting) and water into vapour (evaporation).
- Cooling converts water vapour into water (condensation) and water into ice (freezing).
5. What are the conditions that affect the rate of evaporation?
The rate of evaporation is affected by:
- Exposed surface area: Larger area increases evaporation.
- Humidity: Lower humidity increases evaporation.
- Air movement: More wind speeds up evaporation.
- Temperature: Higher temperatures lead to faster evaporation.
6. Why does evaporation cause a cooling effect?
Evaporation absorbs heat from the surroundings, which leads to a drop in temperature, causing a cooling effect.
7. Why do water droplets form on the outer surface of a glass containing ice water?
Water droplets form due to condensation. Water vapour in the air cools when it comes into contact with the cold surface of the glass, turning into liquid droplets.
8. How can you convert water into ice?
Water can be converted into ice by placing it in a freezer or exposing it to cold temperatures.
9. How do clouds form?
Clouds form when water vapour in the air rises, cools, and condenses into tiny water droplets around dust particles. These droplets cluster together to form clouds.
10. What is the water cycle?
The water cycle is the continuous movement of water on, above, and below the Earth’s surface. It involves processes like evaporation, condensation, precipitation, and collection in water bodies.
11. What is the role of dust particles in cloud formation?
Dust particles act as condensation nuclei. Water vapour condenses around them to form tiny water droplets, which eventually cluster together to create clouds.
12. What is the importance of conserving water?
Conserving water is crucial because:
- Only a small portion of Earth’s water is usable.
- Rising population increases water demand.
- Pollution and misuse reduce the availability of clean water.
Using water wisely and reducing waste is essential.
13. Why does water in an earthen pot feel cooler than in a steel pot?
The porous surface of an earthen pot allows water to seep through. This water evaporates, absorbing heat from the pot and cooling the stored water.
14. How can you speed up the drying of clothes on a rainy day?
To speed up drying clothes on a rainy day:
- Use a fan to increase air movement.
- Spread the clothes in a well-ventilated area.
- Use a dehumidifier if available to reduce air humidity.
15. How do you explain the cooling effect of hand sanitizer?
Hand sanitizer evaporates quickly, absorbing heat from the skin during the process, which causes a cooling sensation.
16. What is the relationship between evaporation and humidity?
Higher humidity slows down evaporation because the air is already saturated with water vapour. Lower humidity speeds it up.
17. How do temperature and air movement affect evaporation?
- Higher temperatures increase the energy of water molecules, speeding up evaporation.
- Faster air movement removes water vapour from the surface, allowing more water to evaporate.
18. Can water vapour exist at room temperature?
Yes, water vapour exists in the air even at room temperature as part of the humidity.
19. What happens when you sprinkle water on a hot surface?
The water evaporates quickly, producing steam. This is because the heat increases the rate of evaporation.
20. How does the smell of food spread even if you’re not in the kitchen?
The smell of food spreads because aromatic molecules evaporate and disperse in the air, carried to your nostrils.
21. Why do clothes dry faster in sunlight?
Sunlight provides heat, which increases the rate of evaporation, causing water in the clothes to evaporate more quickly.
22. Why do we feel cool under a fan?
The fan increases air movement, helping sweat to evaporate faster. This process absorbs heat from the skin, creating a cooling effect.
23. What happens to the level of water in a glass containing ice as the ice melts?
The water level remains constant because the melted ice displaces the same amount of water as its solid form.
24. What is the connection between the water cycle and rainfall?
Rainfall is part of the water cycle, where water evaporates, condenses into clouds, and falls as rain, replenishing Earth’s water sources.
25. Why is water conservation important for the future?
Water conservation is vital to:
- Ensure enough water for future generations.
- Maintain ecological balance.
- Prevent scarcity due to overuse and pollution.
Would you like me to expand on any particular topic or activity? 😊
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