Combustion and Flame– EWF- 4

Why some substances burn with a flame while as some burn without a flame?

What is the first statement of this audio clip?

• The substances which vapourise during burning, give flames.

• For example, kerosene oil and molten wax rise through the wick and are vapourised during burning and form flames.

• Charcoal, on the other hand, does not vapourise and so does not produce a flame.

Why some substances burn with a flame while as some burn without a flame?

What is the second statement of this audio clip?

• The substances which vapourise during burning, give flames.

• For example, kerosene oil and molten wax rise through the wick and are vapourised during burning and form flames.

• Charcoal, on the other hand, does not vapourise and so does not produce a flame.

Why some substances burn with a flame while as some burn without a flame?

What is the third statement of this audio clip?

• The substances which vapourise during burning, give flames.

• For example, kerosene oil and molten wax rise through the wick and are vapourised during burning and form flames.

• Charcoal, on the other hand, does not vapourise and so does not produce a flame.

What are the conditions necessary for combustion to take place? What is the first statement of this audio clip?

                              

• Presence of a combustible substance (fuel)

• Presence of air or oxygen

• Heating the combustible substance to its ignition temperature

What are the conditions necessary for combustion to take place? What is the second statement of this audio clip?

                              

• Presence of a combustible substance (fuel)

• Presence of air or oxygen

• Heating the combustible substance to its ignition temperature

What are the conditions necessary for combustion to take place? What is the three statement of this audio clip?

                              

• Presence of a combustible substance (fuel)

• Presence of air or oxygen

• Heating the combustible substance to its ignition temperature

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.

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What should be done if the clothes of a person catch fire accidentally? Why? What is the first statement of this audio clip?

• When the clothes of a person catch fire the person is covered with a blanket to extinguish fire

• Because when the burning clothes of a person are covered with a blanket, the supply of air to the burning clothes is cut off and hence the burning stops.

What should be done if the clothes of a person catch fire accidentally? Why? What is the second statement of this audio clip?

• When the clothes of a person catch fire the person is covered with a blanket to extinguish fire

• Because when the burning clothes of a person are covered with a blanket, the supply of air to the burning clothes is cut off and hence the burning stops.

When a fire brigade arrives at a place where a building is on fire, what does it do? What is the first statement of this audio clip?

• It pours water on the fire. Water cools the combustible material so that its temperature is brought below its ignition temperature.

• This prevents the fire from spreading.

• Water vapours also surround the combustible material, helping in cutting off the supply of air.

• So, the fire is extinguished.