Available Answers

1. 1.

   Check point:

   1. Which is not a physical change?
      1. Drying of hair
      2. Ironing of clothes
      3. Melting of ice-cream
      4. Burning of paper
   2. This cannot prevent rusting of iron.
      1. Alloying
      2. Greasing
      3. Dipping in water
      4. Galvanization
   3. The gas produced when baking soda is added to vinegar is _______________.
      1. Carbon dioxide
      2. Ozone
      3. Oxygen
      4. Hydrogen
   4. The chemical representation of rust is _______________.
      1. CaCO₃
      2. Fe₂O₃
      3. MgO
      4. Ca(OH)₂
   5. Magnesium oxide + water.
      1. Sodium hydroxide
      2. Calcium hydroxide
      3. Magnesium hydroxide
      4. None of these
2. 2.

   True-False:

   1. Tearing of paper into pieces is a chemical change.
   2. Stainless steel does not rust.
   3. Rusting of iron is a physical change.
   4. The process of depositing a layer of iron on zinc is called galvanization.
   5. Photosynthesis is a chemical change.
3. 3.

   Fill in the blanks:

   1. Melting of ice is a __________________ change.
   2. Changes in which new substances are formed are called __________________.
   3. __________________ and __________________ are used to prevent rusting.
   4. Carbon dioxide gas turns __________________ milky.
   5. Copper sulphate solution is __________________ in colour. When an iron nail is dipped in it, its colour changes to __________________.
4. 4.

   Match the following:

   Physical Change	1. Photosynthesis	Chemical Change
   	2. Melting of wax
   	3. Burning of coal
   	4. Digestion of food
   	5. Dissolving salt in water
   	6. Heating aluminium to make foil

    

5. 5.

   Give the chemical formula of lime water.

6. 6.

   What is the chemical name and formula of rust?