Friday, January 1, 2021

SOLUTIONS OF WORKSHEET 2 of CHAPTER16 : WATER : A PRECIOUS RESOURCE

 Answer 1:

(d) According to the recommendation of United Nations (UN) minimum 50 litres of water per person per day should be provided.
Hence, three buckets (nearly 60 litres) of water is sufficient for a person for one day.

Answer 2:
(a) Most of the water present on earth is not fit for consumption by us. Sea and oceans contain salty water which cannot be drunk. Even most of the fresh water is frozen as ice in glaciers and polar regions.
Hence, we are left with limited amount of water from lake, river and under the ground.

Answer 3:
(a) Snow and ice are frozen while water vapour is in gaseous state. Water from lake and river are in liquid state.

Answer 4:
(b) The upper limit of the layer where water is present between particles of soil and gaps between rocks is called water table and water below this layer is called groundwater.

Answer5:
(c) Among the given options, drip irrigation is a way to use water economically because the installation of drip irrigation techniques require less amount of water.

Answer 6:
(a) 22 March is celebrated as the World Water Day.

Answer 7:
(d) The amount of water recommended by the United Nations for drinking, washing, cooking and maintaining proper hygiene is a minimum of 50 litres per person per day.

Answer 8:
(c) Every drop of water is precious for life to sustain on earth.

Answer 9:
(d) Water cycle does not involve rainwater harvesting. Rainwater harvesting involves recharging the groundwater.

Answer 10:
(a) A pukka or cemented floor is usually impervious to water, inhibiting the seepage of rainwater into grounds.

Answer11:
(a) True
(b) False, snow is also solid form of water.
(c) True
(d) True

Answer 12:
(a) Aquifer is groundwater stored between layers of hard rock below the water table.
(b) The process of seeping of water in the ground is called infiltration.
(c) The evaporation of water from oceans and its arrival back into oceans is called water cycle.

Answer 13:
(a) The source of water in wells is groundwater.
(b) The source of water on ground is rain.
(c) The source of water in atmosphere is evaporation.

Answer 14:
(a) False, the process of seeping of water into the ground is called infiltration.
(b) False, 71% of earth surface is covered with water.
(c) True
(d) True

Answer 15:
(c) water, soil, infiltration

Answer16:
The complete table is given below:
NCERT Exemplar Problems Class 7 Science – Water A Precious Resource-19s
Answer 17:
(a) Solid
(b) Gaseous
(c) Well
(d) Lake
(e) Ice


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