NCERT 6th Class (CBSE) Science: Water and Its Importance

Question: Define the following:

Answer:

1. 1. Ground water: When rainwater falls the water gets absorbed by the soil and is collected under the ground. This is called groundwater.
   2. Water table: The level of ground water is called the water table. It is the level below which the ground is saturated with water.
   3. Flood: Arise in the normal water level in water bodies like lakes, rivers and ponds in certain areas as a result of heavy rainfall over a long period it causes lot of damage to life and property such condition are called flood.
   4. Drought: A decrease in the normal water level in water bodies like lakes, rivers and ponds as a result of no rainfall over a long period of time. This causes a lot of damage to the life of human, animals and aquatic life.

Question: Suppose you want to dry your school uniform quickly. Would spreading it near an anghiti or heater help you? If yes, how?

Answer: Yes, to dry the school uniform quickly, the uniform is spread near an anghiti or heater because evaporation is rapid at higher temperature. Higher the temperature faster is the rate of evaporation. So the uniform is dried up quickly.

Question: 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 cooled water bottle has very cold exposed surface. Due to cool surface there is condensation of water-vapour from air on the surface of water bottle because water vapour is present in atmosphere. The condensed water molecules spread around the bottle. So a puddle of water is noticed after sometime.

Question: To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet?

Answer: The breathe out gases contain water-vapour. The water-vapour condenses at spectacles so glass becomes wet and with the help of small amount of water, it is easy to clean the spectacles.

Question: How are clouds formed?

Answer: The water present on the earth evaporates due to heating by the sun. The water vapour in the air condenses to form tiny droplets of water at high altitude, which appears as clouds. Thus clouds are formed by the condensation of water vapours present in air at high altitude.

Question: When does a drought occur?

Answer: If there is no rain for a long period or for many years then there is scarcity of water in that region. This leads to drought.

Question: Write the sources of water on the earth.

Answer: Sources of water on the earth are: 

1. Seas
2. Oceans
3. Rivers
4. Springs
5. Tubewells