Textbook Solution: Water - A Precious Resource | Class 7 Oxford Science: Chapter Notes, Worksheets & Tests PDF Download

A. Choose the correct option.
1.
Ans: (d)

2.
Ans: (d)

3.
Ans: (a)

4.
Ans: (c)

5.
Ans: (a)

6.
Ans: (d)

B. Fill in the blanks with the correct words.

C. Name the following.

D. Answer the following questions.

1.
Ans: The forms of water on Earth include its solid state, liquid state, and gaseous state. In its solid state, water is present in the form of glaciers, icebergs, snow, hail, and frost. In its liquid state, water is present in water bodies like rivers, lakes, oceans, and seas, and it also exists as water droplets in clouds. In its gaseous state, water is present as water vapor, fog, and steam.

2.
Ans: The term 'water cycle' refers to the continuous circulation of water in nature, also known as the hydrological cycle. It involves four main physical processes: evaporation, transpiration, condensation, and precipitation. Water is evaporated from the earth's surface into the atmosphere, where it condenses to form clouds. Precipitation then returns the water to the earth's surface, completing the cycle.

3.
Ans: Water is used for agriculture, domestic use, and industrial use. In India, the maximum usage of water is in agriculture. This is because 90% of fresh water is used for irrigation, especially in areas where rainfall is unpredictable. In such areas, the only source of water for crops is rain, so less or no rainfall can lead to decreased or no yield.

4.
Ans:  In India, people get water for domestic purposes from water bodies like rivers and lakes through the municipal water distribution system or it is drawn from underground through motor-driven tube-wells. Before it reaches homes, water from these sources is treated in water treatment plants.

5.
Ans: Surface water is water present on the surface of the Earth, in bodies like rivers, lakes, streams, and ponds. It is replenished by precipitation and the melting of glaciers. Groundwater, on the other hand, is water present under the ground, also known as aquifer. This water is replenished by rain, which percolates through the porous layers of the soil and collects underground.

6.
Ans: The water table is the top level of the underground water. A spring is formed when water flows out of the ground to the surface.

7.
Ans: Monsoons are important for our country because they replenish fresh water sources like rivers, lakes, and groundwater. Almost 70% of agriculture in India depends on timely and appropriate onset of monsoons.

8.
Ans: Scarcity of water is defined as the lack of sufficient water to satisfy normal requirements. Factors responsible for it include increasing population, urbanization, increasing industries, deforestation, agricultural activities, and human interference.

9.
Ans: The causes for scarcity of water in India include irregular rains, over-reliance on groundwater for watering crops, pollution of existing water sources, and the discharge of untreated wastes directly into water bodies.

10.
Ans: We need to conserve water to ensure its availability for the future. Practices that can be adopted to conserve water include preventing pollution of water bodies, regulating the usage of water in factories and commercial establishments, improving methods of irrigation, and preventing wastage of water in homes.

11.
Ans: Rainwater harvesting refers to the practice of collecting rainwater during the monsoon season on the roofs of houses and storing it in underground tanks for later use.

12.
Ans: Drip irrigation is a method where water is supplied drop-by-drop at the base of the plant. It is advantageous because it saves a large amount of water and is more efficient for watering crops.