Q62. Place a piece of burning wood or charcoal on an iron plate or Tawa. Cover it with a glass jar or a tumbler, or a transparent plastic jar. Observe what happens. Does charcoal stop burning after sometime? Can you think of the reason why it stops burning?
Q63. Explain how the use of CNG in automobiles has reduced pollution in our cities.
Q64. Arrange the following fuels in the increasing order of their calorific value.
cow dung cake, petrol, wood, LPG, hydrogen
Q65. Make a labelled diagram of a candle flame.
Q66. What is matchstick made of?
How do matchsticks work?
Does a matchstick burn by itself? How does it burn?
Q67. Compare LPG and wood as fuels.
Why is LPG a better domestic fuel than wood?
Q68. What are the harmful effects of burning fuels?