Chapter 7 | Combustion | Class- 8 DAV Science Solutions

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Are you looking for DAV Books Solutions then you are in right place, we have discussed the solution of Science class 8 book Chapter 7 Combustion which is followed in all DAV School. Solutions are given below with proper Explanation please bookmark our website for further updates!! All the Best !!

DAV Class- 8 Science  Combustion Question and Answer

Something To Know

A. Fill in the blanks.

1. A good fuel should have its ignition temperature above the room temperature.

2. Burning of cowdung cakes is an example of slow combustion.

3. The innermost zone of a candle flame, is the coldest.

4. The non-luminous zone of a candle flame is the outemost part of the flame.

5. During incomplete combustion of a fuel, carbon monoxide gas is formed.

B. State True or False for the following statements.

1. Coal is an inflammable fuel. False
2. The outermost part of a candle flame contains unburnt carbon particles. False
3. The heat produced, by burning completely one kilogram of a given fuel, is known as the efficiency of that fuel. True
4. All solid fuels have a higher calorific value than liquid and gaseous fuels. False
5. Sulphur dioxide gas, produced during combustion of fossil fuels, causes acid rain. True


C. Tick (✓) the correct option.

1. An example of a non-combustible substance is-

Answer: iron

2. A fuel starts burning only when it is heated to-

Answer: its ignition temperature

3. The highest temperature zone of a candle flame, is its-

Answer: blue zone

4. The amount of heat produced, on complete burning of 10 kg of a given fuel, in pure oxygen, equals H kilojoule. The calorific fuel, of that fuel, would equal-

Answer: (0.1 H) kJ/kg

5. The gas produced, due to incomplete combustion of carbon fuels, is-

Answer: carbon monoxide

D. Answer the following questions in brief.

1. Define the term ‘combustible material’? Give two examples of combustible materials.

Answer: 

2. State the three conditions that are needed for combustion to take place.

Answer: 

3. State the condition under which ‘slow combustion of a material takes place.

Answer: 

4. Define ‘calorific value of a fuel.

Answer: 

5. State any two characteristics of an ideal fuel.

Answer: 

6. Why is water not used in controlling electrical fires?

Answer: 

E. Answer the following questions.

1. Draw a diagram showing the different zones of candle flame. Label the zone which contains:

(a) unburnt vapours of wax.

Answer: Innermost zone

(b) unburnt carbon particles.

Answer: Middle zone

2. Calorific value of wood is 18,000 kJ/kg. How much of wood is required to produce 360,000 kJ of heat energy?

Answer:

3. Why are gaseous fuels considered better than liquid or solid fuels.

Answer: 

4. Why do we say that ‘burning of fuels’ can cause ‘health hazards’?

Value Based Question

Do it yourself

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