# NCERT Solutions for Class 8 Science Science - NCERT Solution Chapter 6

## Combustion and Flame Class 8

### Exercise : Solutions of Questions on Page Number : 75

Q1 :

List conditions under which combustion can take place.

Combustion is a process of reaction of a substance with oxygen. There are certain conditions required for combustion to take place. They are:

(i) Presence of a fuel

(ii) Air (or oxygen)

(iii) Ignition temperature (minimum temperature at which a substance catches fire)

Q2 :

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 ________ _.

(a) Burning of wood and coal causes __pollution__of air.

(b) A liquid fuel used in homes is __liquefied petroleum gas (LPG)_.

(c) Fuel must be heated to its __ignition temperature__ before it starts burning.

(d) Fire produced by oil cannot be controlled by __water__.

Q3 :

Explain how the use of CNG in automobiles has reduced pollution in our cities.

Q4 :

Compare LPG and wood as fuels.

Q5 :

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.

Q6 :

Make a labelled diagram of a candle flame.

Q7 :

Name the unit in which the calorific value of a fuel is expressed.

Q8 :

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

Q9 :

Which zone of a flame does a goldsmith use for melting gold and silver and why?

Q10 :

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.

Q11 :

Can the process of rusting be called combustion? Discuss.