NCERT Class VIII Science Solutions: Chapter 6-Combustion and Flame Part 7

Question 37:

Forest fire produces a lot of air pollution. Write in brief about the reasons of forest fires.

Answer:

At high temperature, sometimes dry grass catches fire which spreads throughout the forest.
Camp fire may also be a reason.
Human negligence.
Lightening.

Question 38:

Complete the crossword Fig with the help of the clues:

Across:

1. Non-metal which catches fire if exposed to air (10)

3. The lowest temperature at which a substance catches fire is called its __________ temperature. (8)

5. The most common fire extinguisher. (5)

Down:

2. A chemical process in which a substance reacts with oxygen to give off heat. (10)

4. Petrol is used as a __________ in automobiles. (4)

6. It is as hard as stone and black in colour. (4)

Answer:

1. Non-metal which catches fire if exposed to air - Phosphorus

3. The lowest temperature at which a substance catches fire is called its __________ temperature - Ignition

5. The most common fire extinguisher - water

Down:

2. A chemical process in which a substance reacts with oxygen to give off heat - Combustion

4. Petrol is used as a __________ in automobiles - Fuel

6. It is as hard as stone and black in colour - Coal