NCERT 5th Class (CBSE) Science: Air and Water

Question: Describe the different ways by which water can be purified.

Answer: The different ways by which water can be purified are:

1. Boiling
2. Sedimentation and decantation
3. Distillation
4. Filtration
5. Chlorination

Chlorination: In this method chlorine is added to kill the germs in water. Chlorine tablets are also available in the market which can be used for this process.

Purification Of Water

1. Large impurities are removed by sedimentation and decantation. Alum is added to increase the rate of sedimentation (loading).
2. Finer impurities are removed by filtration.
3. Chlorine is added to kill germs (chlorination).
4. Water is stored in big storage tanks to supply to users.
5. Clean water is supplied to users.

Question: Describe the layers of atmosphere.

Answer: The different layers of atmosphere are:

Troposphere:

1. This is the first layer of atmosphere.
2. The weather phenomenon like rain, cloud formation and wind happens in this layer.
3. Living things can survive in this layer.

Stratosphere:

1. This is the second layer of atmosphere.
2. Ozone layer is present in stratosphere which protect us from harmful UV rays radiations that can cause health problems like skin cancer
3. Many jet airplains fly in this layer.

Mesosphere:

1. This is the third layer of atmosphere.
2. It protect us from meteroids by burning them before they can reach the surface of the earth.

Thermosphere:

1. It is the fourth layer of atmosphere.
2. Space shuttles can revolve in this layer.

Exosphere:

1. It is the last layer of atmosphere.