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:

Which among the following is considered as the cleanest fuel?

Choose the incorrect statement from the following.

A good fuel is one which:

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.

Some words (underlined) in the following sentences are jumbled up. Write them in their correct form.

(a) Seldie is a combustible substance.

(b) Slags is a non-combustible material.

(c) Chittsmack does not burn by itself.

(d) Some substances on combustion produce thea and mafel.

(e) The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its ficalroic value.