NCERT Exemplar Solutions: Water | Science Class 6 PDF Download

Ans: (d) 
Drying wet clothes, water gets converted into vapour form. Whereas washing, bathing and cleaning utensils are the activities which require the use of water.

Ans: (b)
Bathing, washing clothes and mopping a room will require a large amount of water. Brushing teeth requires a minimum amount of water.

Ans: (c) 
To make one sheet of paper requires two glasses of water.

Ans: (d)
Water in our tap comes from rivers, lakes or wells. Water is routed through water treatment plants before it gets supplied through taps. The water drawn from these sources is fit for consumption.

Ans: (c) 

Evaporation Evaporation is directly proportional to temperature when temperature increases, evaporation also increases. The temperature in the room will be lower than compared to the temperatures of sunlight, burner and rooftop. So, a glass of water kept in a room has the slowest water evaporation.

Ans: (d) 
Transpiration is a process when the water is lost in the form of vapour which when parts of a plant (mainly leaves) are exposed is termed as transpiration. The loss of water due to transpiration is quite high.

Ans: (a)
Water vapour present in the air condenses to form tiny droplets of water floating in the air which appear to us like clouds. Later these tiny water droplets are formed into larger sized water drops and then get converted to rainfall.

Ans: (d)
Lakes, ponds, rivers and other water bodies are filled up by rainwater. Some rainwater is evaporated back to air. The rest, the soil absorbs the water into the ground and becomes available as groundwater. Hence, wells are fed by this groundwater.

Ans: (d)
Due to heavy rains, the water level rises in rivers, lakes and ponds. This water then spreads over a large area causing floods. In turn crop fields, forests, villages and cities get submerged underwater. Hence, flood causes extensive damage to crops, domestic animals, property and human life.

Ans: (c)
Rainwater harvesting is a method used to collect rainwater. By storing the water, we can increase the availability of water which is collected and stored for later use.

The activities shown in the given figure in which water is being used are:

• Water is used for bathing.
• Water is used for washing clothes.
• Water is lifted from the well to store water and for drinking purposes.

The two activities which require more than a bucket of water are:

• For irrigation purposes, we require more water.
• For washing a large number of clothes.

The two activities which require less than one bucket of water are:

• For brushing teeth.
• For washing hands.

Wet clothes placed on a clothesline get dry after some time because on exposing to sunlight, firstly water present in wet clothes gets converted into water vapour due to evaporation and as a result clothes get dry after some time.

Water gets evaporated when kept under the shade of a tree during daytime due to the air around the tree also gets heated up from the presence of sunlight so water gets evaporated from the heated air.

Areas covered with concrete affect the availability of groundwater because it reduces the entry of rainwater into the ground, which in turn reduces the availability of groundwater.

There is a need for conserving water because:

• With the rise in population, the availability of water is decreasing. The demand for water is increasing day by day. Hence, we need to conserve water for the future.
• The level of groundwater is decreasing drastically due to the change in climate which results in limited usage of water. This would lead to extreme water scarcity and hence we should conserve water for the next generations.

Water, as vapour goes into the atmosphere by the processes of evaporation and transpiration and forms clouds, which on condensation fall in the form of snow and rain.

Most of the water that falls on the land as rain and snow sooner or later goes back to a sea or an ocean because the water that falls on the land as snow melts during summers and flows into the rivers and streams, from there it goes into the sea or oceans. Some water enters into the ground and becomes available to us as groundwater. The groundwater is pumped out for domestic, irrigation and industrial use, which eventually goes into rivers and finally into the seas or oceans.

Here is the diagram which shows the seawater reaching a lake or a pond:

To get the salt back from the water we have two methods to do:

• Water can be removed from the salt solution by heating it on a stove.
• Or by keeping it in the sun on a plate for a few hours for evaporation.

Evaporation is a slow conversion of water into its vapour state. Once the water gets evaporated, we get the salt back.

Rooftop rainwater harvesting – is a method where rainwater is collected from the rooftop to a storage tank, through pipes. This water needs to be filtered before using because it may contain some soil from the roof. Instead of collecting rainwater directly in the tank, the pipes can go directly into a pit in the ground. This then enters into the soil to recharge or refill the groundwater.
Here is the diagram which shows the process of rooftop rainwater harvesting: