Available Answers

1. 1.

   Classify the following as physical or chemical change. Think of the reason in your mind:

   1. Heating wax
   2. Switching an electric bulb
   3. Baking of potatoes
   4. Ripening of a fruit
   5. Making butter from cream
   6. Burning of coal
   7. Cooking of vegetables
   8. Cutting of fruits
   9. Burning of phosphorus
   10. Gemination of seed
   11. Setting of cement
   12. Breathing by humans
   13. Respiration by cows
   14. Heating of ammonium chloride convert sulphur dioxide to sulphur dioxide
2. 2.

   Classify the shown pictures into physical and chemical changes:

   

3. 3.

   Classify the following reactions on the basis of the terms given below:

   Thermal reaction, Electrolytic reaction, Catalytic reaction, Photochemical reaction.

   1. 2KCIO₃ →^MnO₂ 2KCI + 3O_{2 __________________________}
   2. Fe + S →^Δ FeS _{__________________________}
   3. H₂ + Cl₂^Diffused→_Sunlight 2HCI _{__________________________}
   4. 2H₂O(I)  ^electric→_current 2H₂(g)+ O₂(g) _{__________________________}
4. 4.

   Fill in the blanks with suitable words:

   1. Chemical reactions occur when the substances are brought in _____________ contact.
   2. Iron and Sulphur combine to form _____________
   3. _____________ is the catalyst to convert sulphur dioxide to sulphur trioxide.
   4. _____________ acts as a promoter during manufacture of ammonia.
   5. If _____________ are more, the rate of reaction is more.
5. 5.

   TICK (√) THE CORRECT CHOICE AMONGST THE FOLLOWING:

   1. Which of the following is a chemical property?

   1. Density
   2. Solubility
   3. Reaction with acid
   4. Colour

   2. The catalyst used to convert SO₂ to SO₃ is:

   1. Iron
   2. Platinum
   3. Asbestos
   4. Vanadium pentaoxide

   3. Gas evolved when potassium chlorate is heated

   1. Chlorine
   2. Bromine 
   3. Hydrogen chloride
   4. Oxygen

   4. Frequency of collisions is maximum in:

   1. Solids
   2. Liquids 
   3. Gases
   4. None of above

   5. Sodium reacts with water to liberate _______________ gas.

   1. Oxygen
   2. Hydrogen
   3. Nitrogen 
   4. Chlorine
6. 6.

   FILL IN THE BLANKS WITH SUITABLE WORDS:

   1. Heat increases the temperature and in turns increases its _____________.
   2. Reactions that take place when exposed to light _____________.
   3. A substance formed when iron and sulphur are heated _____________.
   4. Magnetization of a soft iron bar is an example of _____________ change.
   5. The composition of a substance _____________ during a chemical change.