Available Answers

1. 1.

   Tick (√) the correct option:

   1. Burning of a substance in the presence of air is known as
      1. rusting
      2. combustion
      3. reduction
      4. corrosion
   2. Which one of the following is not a combustible substance?
      1. Paper
      2. Glass
      3. Petrol
      4. Diesel
   3. When coal is burnt, it produces
      1. oxygen
      2. carbon dioxide
      3. methane
      4. ethane
   4. How many zones are there in the flame of a candle?
      1. Two
      2. Three
      3. Four
      4. Five
   5. The colour of the outermost zone of the flame is
      1. blue
      2. yellow
      3. red
      4. green
   6. In which zone of the of the flame, complete combustion of vapour takes place?
      1. Non-luminous zone
      2. Luminous zone
      3. Zone of no combustion
      4. Blue zone
   7. In which zone of the flame incomplete combustion takes place?
      1. Non-luminous zone
      2. Blue zone
      3. Luminous zone
      4. Zone of no combustion
   8. The zone of the flame where almost no combustion takes place is
      1. blue zone
      2. zone of no combustion
      3. luminous zone
      4. non-luminous zone
   9. In which zone of the flame, carbon particles burn incompletely to produce carbon monoxide?
      1. Zone of no combustion
      2. Luminous zone
      3. Blue zone
      4. Non-luminous zone
   10. The zone of the candle flame which is hottest is called
       1. blue zone
       2. non-luminous zone
       3. luminous zone
       4. zone of the no combustion
   11. A fuel X which neither leaves any residue on burning nor does it emit any smoke on combustion. The fuel X is
       1. Coal
       2. Wood
       3. LPG
       4. Charcoal
   12. An example of slow combustion is
       1. To burning a piece of paper
       2. To burn wick dipped in kerosene
       3. Rusting of iron
       4. To burn domestic gas
2. 2.

   Fill in the blanks:

   1. On burning, solid fuels leave ____________ and ____________.
   2. Fuels are compounds of ____________ and ____________.
   3. P₄ + 5O₂ → ____________ + ____________.
   4. Materials such as glass, metals, ceramics, etc. are known as ____________ materials.
   5. The innermost zone of flame is known as ____________.
   6. Sodium is kept immersed in ____________ and phosphourus in ____________.
3. 3.

   Tick (√) the correct and cross (x) the wrong statement:

   1. Substances burn in air and form carbon dioxide.
   2. Burnt fuel should always leave some residue.
   3. Water gas is a mixture of carbon monoxide and nitrogen.
   4. Calorfic value of coke is more than that of coal.
   5. Natural gas mainly contains methane and traces of ethane and propane.
   6. Wood burns with a flame.
   7. There is a blue colour zone at the base of the wick.
   8. Presence of a combustible substance is not essential for a substance to burn.
   9. Red phosphorus can be stored in a bottle.
   10. Coal gas is obtained from destructive distillation of coal.
4. 4.

   Match the following:

   Column A	Column B
   1. Candle	(a) Kerosene
   2. Sodium	(b) Destructive distillation
   3. Blown out candle	(c) Fractional distillation of petroleum
   4. Coal	(d) Methane
   5. Diesel	(e) Rusting
   6. Paper	(f) Coal
   7. Natural gas	(g) Foul smell
   8. Slow combustion	(h) Smelly stream of gas
   9. Thermal power	(i) Combustible
   10. Ethyl mercaptan	(j) Flame

    

5. 5.

   Find the odd one out:

   1. Diesel, kerosene, stone and petrol.
   2. Natural gas, gobar gas, hydrogen, biogas
   3. Wood, coal, coke and diesel
   4. Burning of paper, candle wick, kerosene and oxidation of food.
6. 6.

   What happens to natural gas when it is burnt?