Available Answers

1. 1.

   Choose the correct answer.

   1. The blanket of air that covers the earth is called
      1. lithosphere
      2. hydrosphere
      3. atmosphere
      4. biosphere
   2. The ozone layer is found in
      1. troposphere
      2. stratosphere
      3. ionosphere
      4. exosphere
   3. The component of air that cannot be used directly by the living beings, is
      1. oxygen
      2. nitrogen
      3. carbon dioxide
      4. water vapour
   4. The component of air that helps in burning, is
      1. oxygen
      2. carbon dioxide
      3. dust
      4. smoke
   5. Diseases like asthma, bronchitis etc. are caused due to 
      1. polluted water
      2. polluted air
      3. deficiency of minerals
      4. lack of food
   6. The process in which impure muddy water is allowed to stand undisturbed in a container, is called
      1. filtration
      2. sedimentation
      3. decantation
      4. evaporation
   7. The easiest and most common method to purify water before consumption is
      1. distillation
      2. boiling
      3. chlorination
      4. all of these
   8. Purification of water first by evaporation and then by condensation is called
      1. distillation
      2. sedimentation
      3. filtration
      4. bleaching
   9. Things like syringe, dropper, drinking straw work on the principle of
      1. water pressure
      2. air pressure
      3. pressure of container
      4. all of these
   10. Aquatic plants and animals get air dissolved in
       1. water
       2. atmosphere
       3. plants
       4. none of these
2. 2.

   What is the contamination of air with undesirable substances called?
3. 3.

   Name one method of separating insoluble impurities from water.
4. 4.

   What is the main source of water?
5. 5.

   Name the various layers of atmosphere.
6. 6.

   What is the composition of air?