NCERT 7th Class (CBSE) Science: Water: A Precious Resource

Question: Explain how groundwater is recharged?

Answer: The rainwater and water from other sources such as rivers and ponds seeps through the soil and fills the empty spaces and cracks deep below the ground. The process of seeping of water into the ground is called infiltration. The groundwater thus gets recharged by this process.

Question: Enlist some methods to conserve water.

Answer: Water conservation is process of preventing wastage of water, using water carefully and recharging ground water. Water conservation can be done by:

1. Repairing leaking pipes and taps.
2. Not wasting water during brushing teeth, shaving, bathing, washing clothes and during other activities.
3. Rainwater harvesting.
4. By drip irrigation of plants.

Question: Explain the term “underground water”.

Answer: Groundwater is the water found underground in the cracks and spaces in soil, sand and rock. Rainwater gets collected in the soil by seeping (leaking) into the gravel and rocks at the bottom. The seepage of rainwater from the surface of the soil is called infiltration. the level underground where all the space between the soil particles and rocks is filled with water is called water table. An aquifer is the groundwater stored between the the hard rock layer below the water table.

Question:What do you understand by anomalous expansion of water?

Answer: When water at room is cooled, it contract until reaches 40°C and then starts expanding. This strange behaviour of water is called anomalous expansion of water.

Question: What is the reason behind floating of ice in water?

Answer: Ice is lighter than water so it floats on water.

Question: Define specific heat capacity of substance?

Answer: The amount of heat required to raise the temperature of substance is known as specific heat capacity of substance.

Question: Water is a universal solvent. Explain.

Answer: A large number of substances dissolve in water so it is called universal solvent. A liquid that dissolve another substance (solute) to form solution is called solvent.