CLASS-VIII
COMBUSTION
ASSIGNMENT-4
Q1. Fill in the blanks:
a) Fuel must be heated to its______________________ before it starts burning.
b) Fire produced by oil cannot be controlled by ________________.
c) ______________ is essential for combustion.
d) Fuel efficiency is expressed in units ___________.
e) ________________ fuels have highest calorific value.
f) Incomplete combustion of carbon produces __________________________ gas.
g) Complete combustion of carbon produces ___________________________ gas.
h) ___________________________ is the coldest part of the flame.
i) Luminous zone is _______________ in colour.
j) _________ phosphorous is present in matchstick.
Q2. What are inflammable substances? Give example.
Q3. Name 4 types of combustion. Give one example of each.
Q4. Differentiate between rapid and spontaneous combustion.
Q5. Name the unit in which the calorific value of a fuel is expressed.
Q6. Explain how CO2 is able to control fires.
Q7. Which substances on burning give a flame?
Q8. Camphor burns with a flame, but charcoal glows. Why?
Q9. Which zone of a flame does a goldsmith use for melting gold and silver and why?
Q10. What is the basic principle in controlling fire?
Q11. Give reasons:
i) Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not.
ii) It is difficult to burn a heap of green leaves but dry leaves catch fire easily.
Q12. 1kg of LPG produces 55000 kJ of energy. What is the calorific value of LPG?
Q13. In an experiment 4.5kg of a fuel was completely burnt. The heat produced was measured to be 1,80,000 kJ. Calculate the calorific value of the fuel.
Q14. 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?
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