Available Answers

1. 1.

   Complete the statements given below pertaining to - water.

   1. The molecular formula of water is H₃O / H₂O / HO.
   2. Water exists above the earth's surface in the form of springs/fog and on the earth's surface as clouds / dew / vast oceans.
   3. Henry Cavendish concluded through experiments that water is not an element by a mixture/compound of nitrogen/hydrogen & oxygen combined in the ratio 2:1 / 1:1 / 3:1.
   4. About 1/4, 5/6, 3/4 of the earth's surface is covered by water in the form of vast oceans.
   5. The percentage water content in the human body is about 10%/  25% / 70%.
   6. Water obtained from wells, lakes, rivers, oceans etc. is called - mineral water / natural water.
   7. The purest form of natural water is - 
      river water/lake water/rain water/well water.
   8. The most impure form of water is -
      well water/sea water/river water.
2. 2.

   Potable water should be clear & colourless. Give reasons.

3. 3.

   Potable water should be free from bacteria & germs. Give reasons.

4. 4.

   Potable water should not contain salts - such as cyanides & urea. Give reasons.

5. 5.

   Potable water should contain dissolved gases & minerals. Give reasons.

6. 6.

   Saline water & sea water are unfit for human comsumption. Give reasons.