Fill in the blanks in the following sentences.
(a) A ____________ process in which a substance reacts with
__________ to give off heat is called combustion.
(b) When the clothes of a person catch __________, the person is
covered with a __________ to extinguish fire.
(c) The __________ temperature at which a substance catches
fire is called its __________ temperature.
(d) The substances which have very ________________ ignition
temperature and can easily catch fire with a flame are called
__________ substances.
(e) The substances which vapourise during __________, give flame.
Shyam was cooking potato curry on a chulha. To his surprise he
observed that the copper vessel was getting blackened from
outside. It may be due to:
(a) proper combustion of fuel.
(b) improper cooking of potato curry.
(c) improper combustion of the fuel.
(d) burning of copper vessel.
Choose the incorrect statement from the following.
A good fuel is one which:
(a) is readily available.
(b) produces a large amount of heat.
(c) leaves behind many undesirable substances.
(d) burns easily in air at a moderate rate.
Which among the following is considered as the cleanest fuel?
(a) cow dung cake (c) kerosene
(b) petrol (d) hydrogen gas
In villages, people use wood as fuel because:
(a) it is considered to be an ideal fuel.
(b) of its easy availability and low cost.
(c) it is environment friendly.
(d) it catches fire easily.
The calorific value of a fuel is expressed in a unit called
(a) kilojoule per litre (c) kilojoule per gram
(b) kilogram per mililitre (d) kilojoule per kilogram
Choose the incorrect statement from the following.
Forest fires are usually due to:
(a) carelessness of humans (c) cutting of trees
(b) heat of sun (d) lightning strike
Choose the correct statement about inflammable substances from
the following.
They have:
(a) low ignition temperature and cannot catch fire easily.
(b) high ignition temperature and can catch fire easily.
(c) low ignition temperature and can catch fire easily.
(d) high ignition temperature and cannot catch fire easily
The substance expected to have the highest ignition temperature
out of the following is
(a) kerosene (c) coal
(b) petrol (d) alcohol
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