Fill in the blanks:
- The process of changing of water into its vapour is called _________________.
- The process of changing water vapour into water is called _________________.
- No rainfall for a year or more may lead to _________________ in that region.
- Excessive rains may cause _________________.
State for each of the following whether it is due to evaporation or condensation:
- Water drops appear on the outer surface of a glass containing cold water.
- Steam rising from wet clothes while they are ironed.
- Fog appearing on a cold winter morning.
- Blackboard dries up after wiping it.
- Steam rising from a hot girdle when water is sprinkled on it.
Answer the following questions:
Question 1: Suppose you want to dry your school uniform quickly. Would spreading it near an anghiti or heater help? If yes, how?
Answer: Spreading the school uniform near an angithi or heater would help in drying it quickly. The heat from the heater increases the temperature which increases the rate of evaporation. Moreover, spreading the cloth increases the surface area which also increases the rate of evaporation.
Question 2: Take out a cooled bottle of water from refrigerator and keep it on a table. After some time you notice a puddle of water around it. Why?
Answer: The water vapour present in the atmosphere condenses because of low temperature of water bottle. The vapour thus turns into water droplets around on the outer surface of the bottle. Water droplets cumulate and fall down to make a puddle.
Question 3: To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.
Answer: When a person breathes out on glasses, some amount of water vapour also comes out in exhaled air. This water vapour condenses on the glasses and thus the glasse become wet.
Question 4: How are clouds formed?
Answer: When water vapour reaches high in the atmosphere, it condenses and thus clouds are formed.
Question 5: When does a drought occur?
Answer: Prolonged spell of no rain at a place results in drought.
Which of the following statements are “true”?
- Water vapour is present in air only during the monsoon.
- Water evaporates into air from oceans, rivers and lakes but not from the soil.
- The process of water changing into its vapour, is called evaporation.
- The evaporation of water takes place only in sunlight.
- Water vapour condenses to form tiny droplets of water in the upper layers of air where it is cooler.
Answer: 1 False, 2 False, 3 True, 4 False, 5 true