Available Answers

1. 1.

   Tick (√) the appropriate answer:

   1. Water which is free from impurity and fit for human consumption is known as:
      1. Hard water
      2. Potable water
      3. Soft water
      4. Clean water
   2. Organic waste in water comes mainly from:
      1. Industries
      2. Chimneys
      3. Sewage
      4. Aeration
   3. Alum is used in the process of:
      1. Sedimentation
      2. Loading
      3. Filteration
      4. Aeration
   4. Chlorination is commonly done by using:
      1. Chlorine gas
      2. Hydrogen chloride
      3. Sulphuryl chloride
      4. Bleaching powder
   5. Heat treatment given to water kills germs. The process is:
      1. Aeration
      2. Filteration
      3. Chlorination
      4. Boiling
   6. Which plants use dissolved gases in water?
      1. Aerial plants
      2. Aquatic plants
      3. Submerged plants
      4. Desicated plants
2. 2.

   Fill in the blanks with suitable words:

   1. ______________ plants use dissolved gases in water.
   2. ______________ reactions take place in our body.
   3. Water is used as a _______________ in car radiators.
   4. Water helps in transportation of ________________.
   5. ________________ absorb the minerals dissolved in water.
3. 3.

   Write true or false:

   1. Distilled water is fit for drinking.
   2. Sea water is saline due to high salt content.
   3. The process in which light particles become heavy due to chemicals and settle down is known as sedimentation.
   4. Body fluids do not contain water.
   5. Impurities present in water make it fit for drinking.
4. 4.

   Complete the following chart related to purification of water:

   

5. 5.

   Tick (√) the most appropriate answer:

   1. An inflammable gas which is present in water:
      1. Hydrogen
      2. Oxygen
      3. Water vapours
      4. Steam
   2. An apparatus used for electrolysis of water:
      1. Electrolytic cell
      2. Hoffmans cell
      3. Voltametric cell
      4. Hoffmans voltameter
   3. Gas which is collected at cathode when water is electrolysed:
      1. Hydrogen
      2. Oxygen
      3. Chlorine
      4. None of these
   4. Water is formed when plants and animals:
      1. Respire
      2. Digest
      3. Move
      4. Sleep
   5. Pure water boils:
      1. Below 100°C
      2. Above 100°C
      3. At 100°C
      4. None of these
6. 6.

   Fill in the blanks:

   1. At low pressure, the boiling point is also ________________.
   2. Presence of _______________ lower the freezing point of a liquid.
   3. Water shows anomalous or unusual behaviour when heated or cooled between ______________ and ______________.
   4. Density of ice is minimum at _________________.
   5. If volume is decreased, the density ________________.
   6. Water is a _____________ solvent as it dissolves a large variety of substance.
   7. Water turns ____________ cobalt chloride ______________.