NCERT Summary: Water | Science Class 6 PDF Download

Water and Forms of water

• Water is a natural resource which is vital for both plants and animals. It is made up of tiny molecules oxygen and hydrogen.
• Earth surface is covered with water is about three-fourth in ratio. That is why earth is known as water planet.

Forms of water

1. Solid: ice which is found at the poles of the earth. The glaciers and snow covered mountains is solid form of water.
2. Liquid: rivers, lakes, seas and oceans are liquid form of water.
3. Gas: water vapour is present all around us.

Uses of water

• Farmers need lot of water to irrigate the crop, factories need lot of water to produce the items required, water use in our daily life activity like bathing, drinking, washing and cooking etc.

Sources of water

Rain water

• It is a prime source of water.
• Physically rain water is clear, sparkling and bright.
• Bacteriologically rain water is free from pathogenic agents.
• Chemically it is very soft containing traces of dissolved solids.

Surface water

• It is originate from rain water. It is main source of water supply in many areas.
• It is prone to contamination from animal and human sources.
• It needs to purify before use.
• Example: lakes, river, tanks etc.

Ground water

• It is the cheapest and most practical means of providing water to small communities.
• It is superior to surface water because the ground itself provides an effective filtering medium.

Water cycle

• It is a continuous circulation of water in nature is called water cycle.
• It consists in three processes:
  (i) Evaporation: it is a conversation of liquid into vapour is called evaporation.
  (ii) Precipitation: it is falling down of water from clouds is called precipitation.
  (iii) Runoff: it is a process in which the water of the land usually reaching the sea.

Rain water harvesting

• It is a way to increase the availability of water to collect rainwater and store it for later use.
• Collection of rain water in this way is called rain water harvesting.
• Rooftop rain water harvesting: the rain water is collect from the rooftop to a storage tank, through pipes.
• Other option is to allow water to go directly to the ground from the roadside drains that collect rainwater.

Scarcity of water

• It is a situation where there is insufficient water to satisfy normal requirements.
• The factors of scarcity of water are:
  (i) Increasing industries
  (ii) Agricultural activities
  (iii) Increasing population
  (iv) Deforestation