(a) Yes, water exists in three phases:
(i) Water which is liquid phase.
(ii) Ice represents solid phase.
(iii) Steam is the gas phase.
(b) When ice is kept at room temperature, it melts, loosing its solid phase and entering liquid phase by turning into water.
(c) Vineet is an observant and curious person. He asks questions to satisfy his curiosity and readily accepts concepts.

Water is getting polluted:
(i) By industrial waste
(ii) By human activities
Measures to stop water pollution:
(i) We should not throw waste materials and garbage into water.
(ii) We should sensitize people about harmful effects of water pollution.
Associated Value : We should discourage any activity in our life that may cause water pollution

The climate close to the earth's surface is warm. It gets cooled as one go up in atmosphere. Water vapour being lighter, rises up in the atmosphere. At the upper layer of atmosphere, where the temperature is lower the vapour get condensed into tiny water droplets and forms cloud.

The process by which land water returns back to a sea or an ocean is as follows:
(i) Snow/Rain falling on the mountains melts into water that flows down in the form of streams and rivers.
(ii) A part of the rainwater gets absorbed into the ground and rest also flow in the form of stream or rivers.
(iii) The river water after passing through various regions ultimately reaches into a sea or an ocean

Sea water reaches a lake or pond is represented by a diagram:

The common salt dissolved in half a cup of water can be recovered by removing the water from the salt solution. This can be done by heating the solution on a gas stove or keeping it under the sun in a plate for few hours. Due to evaporation of water in both the processes, we will get the salt back.

Water is used:
(i) for drinking and cooking
(ii) for bathing and cleaning.
(iii) in agriculture, to produce food.
(iv) in Industries, to perform different activities

In this process, the rain water is collected from the rooftop to a storage tank, through pipes. This water may contain soil from the roof and need filtering before it is used. Instead of collecting rain water in the tank, the pipes can go directly into a pit in the ground. This then seeps into the soil to recharge the ground water.