Combustion

REVISION ASSIGNMENT

CLASS - VIII

SUBJECT – SCIENCE

TOPIC – COMBUSTION

Q1. Complete the statement-

1.       The gas required for combustion is_______________.

2.       The gas produced in the working of soda-acid type fire extinguisher is __________________.

3.       Burning of LPG at home is an example of ___________________.

4.       The hottest zone of the flame is ______________________. 

5.       ______________ shows the spontaneous combustion.

6.       ________________ can be used to extinguish fire at the petrol pump.

7.       __________________ is the ideal fuel to be used at home.

 Q2. When does a substance start burning?

 Q3. What is acid rain? How is it harmful?

 Q4. Kerosene oil catches fire faster than wood. Why?

 Q5. Why is water poured to extinguish burning wood?

 Q6. In an experiment, 4.5 kg of a fuel was completely burnt. The heat produced was measured to be 180,000 KJ. Calculate                    the calorific value of the fuel.

 Q7. Why petrol cannot be used as a domestic fuel?

 Q8. Why carbon dioxide is often used as fire extinguisher?

 Q9. How is heat and light produced in the sun?

 Q10. Why LPG is a better fuel than kerosene oil?

 Q11. A person sleeping in a closed room with burning coal, feels suffocated after sometime. Why?

 Q12. Hydrogen has the highest calorific value, but it is not used as a fuel. Why?

 Q13. It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Why?

 Q14. Why is a wood used as a fuel in villages? What are the disadvantages of using wood as a fuel?

 Q15. Explain the following on the basis of ignition temperature.

1.       Water can be easily boiled in a paper cup

2.       White phosphorus cannot be kept in air in summer.

3.       How is a matchstick lighted?

4.       Why does the flame of a burning candle goes off on strong blowing?

Q16   A person tried to extinguish the fire at petrol pump by throwing water on it. He was not successful. Why?