Question

It is difficult to burn a heap of green leaves but dry leaves catch fire easily.
10. Which zone of a flame does a goldsmith use for melting gold and silver
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.
Can the process of rusting be called combustion? Discuss.
13. Abida and Ramesh were doing an experiment in which water was to be
8. Explain how CO, is able to control fires.
9.
Explain.
and why?
11.
12.
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 1

1) Green leaves contain less water. Presence of water tends to increase the ignition temperature. So, the heap of green leaves do not catch fire easily.

2)Outermost zone:

The goldsmith uses the outermost zone of the flame to use for melting gold and silver because it is the hottest part of the flame and undergoes complete combustion.

3)Total mass of fuel = 4.5 kg Total heat produced = 180,000 kJ Heat produced by burning 1 kg of fuel = 180,000 kJ/4.5 kg = 40,000 kJ/kg. So, calorific value of fuel = 40,000 kJ/kg.

4)The process of rusting cannot be called combustion due to the following reasons :

• No energy is obtained in a rusting process. Combustion is a chemical process in which a combustible substance reacts with oxygen to produce heat and light whereas in rusting, a metal reacts with oxygen to produce metallic oxide.

Answer 2

Answer:

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