COMBUSTION 8

  Practice Paper     

Subject Chemistry (2019) 

ClASS VIII                         Ch- COMBUSTION                                                

1. Define combustion.                      
2. What are the conditions required for combustion to take place? 
3. List conditions under which combustion can take place. 
4. Carbon dioxide is often used as a fire extinguisher. write two reason for this.
5. What is bio gas?
6. Define ignition temperature.
7. How is heat and light formed in the Sun?
8. When does a substance start burning?
9. Which substance have very low ignition temperature and catch fire easily?
10. What are inflammable substances? Give two example.
11. What is mean by rapid combustion?Give one example.
12. What is meant by spontaneous combustion?Give one example.
13. What is meant by explosive combustion?Give one example
14. what is meant by slow combustion?Give one example.
15. What is a flame?
16. What is meant by calorific value? What is the unit of calorific value?
17. What is meant by global warming?
18. What is acid rain ? how is it harmful?
19. Why is respiration referred to as slow combustion?
20. Why does yellow phosphorous catch fire on its own?
21. A person is sleeping in a closed room with burning coal,feels suffocated after some time.why?             
22. Why do different substances catch fire at different temperature?
23. Which substances burn with flame?
24. How will you put it off if:
    (i) kerosene oil catches fire
    (ii) a fire due to short circuit           
    (iii) fire at petrol pump
    (iv) wood catches fire? 
25. (i)Which zones of the candle flame have the maximum and minimum temperature?                    
    (ii)Which zone of a flame does a goldsmith use for melting gold and silver? 
26. Why does the middle zone of the candle flame glow with yellow color?
27. Camphor burns with flame but charcoal glows.Why?
28. Write any four characteristics of ideal fuel. 
29. Give two examples each of solid fuel,liquid fuel and gaseous fuel.
30. Writ one similarity and dissimilarity between respiration and rusting.
31. Draw a diagram showing different zones of candle flame.
    (i) unburnt vapour of wax  (ii) unburnt carbon particles ?
32. Calorific value of wood is 18000 kJ/kg.How much of wood is required to produce heat energy of 108,000 kJ?
33. 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 fuel?
34. List the health hazards caused by burning of fuel.
35. Why are gaseous fuels considered the best?
36. Why is water not used to control the fire by electric short circuit?
37. What are the constitutions of foam type fire extinguisher?
38. Define fuel efficiency.           NCERT Questions 👇
39. List conditions under which combustion can take place.
40.  Fill in the blanks: 
    (a) Burning of wood and coal causes of air. 
    (b) A liquid fuel, used in homes is . 
    (c) Fuel must be heated to its before it starts burning. 
    (d) Fire produced by oil cannot be controlled by .
41. Explain how the use of CNG in automobiles has reduced pollution in our cities.
42. Compare LPG and wood as fuels.
43.  Give reasons: 
    

    (a) Water is not used to control fires involving electrical equipment. 

    (b) LPG is a better domestic fuel than wood. 

    (c) Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not.
44. Make a labelled diagram of a candle flame.
45. Name the unit in which the calorific value of a fuel is expressed.
46. Explain how CO2 is able to control fires.
47.  It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Explain. 
48. Which zone of a flame does a goldsmith use for melting gold and silver and why? 
49. 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. 
50.  Can the process of rusting be called combustion? Discuss. 
51. Abida and Ramesh were doing an experiment in which water was to be heated in a beaker. Abida kept the beaker near the wick in the yellow part of the candle flame. Ramesh kept the beaker in the outermost part of the flame. Whose water will get heated in a shorter time.