Science

Combustion and Flame

Question:

Compare LPG and wood as fuels.

Answer:

Wood has been a traditional fuel for both domestic and industrial use. However, it produces a lot of smoke that can cause respiratory problems. Also, wood is obtained from trees. Thus, using wood as a fuel causes deforestation. Therefore, slowly wood is replaced by LPG, which is a liquefied form of petroleum gas. It does not give out smoke and other pollutants and is a cleaner fuel. Again, fuel efficiency of LPG is more than that of wood. The calorific value of LPG is 55000 kj / kg, while that of wood is between 17000 to 22000 kj / kg. Hence, LPG is favoured over wood.
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Questions and Answers

Combustion and Flame

Q 1.

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?
Answer

Q 2.

List conditions under which combustion can take place.

Answer

Q 3.

Compare LPG and wood as fuels.
Answer

Q 4.

Explain how C02 is able to control fires.
Answer

Q 5.

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

Q 6.

Make a labelled diagram of a candle flame.

Answer

Q 7.

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

Q 8.

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.
Answer

Q 9.

Can the process of rusting be called combustion? Discuss.
Answer

Q 10.

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.

Answer

Q 11.

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

Q 12.

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