Class 8 Science Chapter 4 MCQ

The substances which give very low ignition, temperature and can easily catch fire with a flame, are called inflammable substances.

Matchstick does not burn by itself. A matchstick is lighted by rubbing it on the rough surface provided on the side of the matchbox. The heat produced by friction arises the temperature of the chemicals present on the matchstick head to their ignition temperature. Due to this, the chemicals present on the head of the matchstick catch fire and the matchstick starts burning.

A good fuel does not produce any harmful gases or leaves and any residue after burning. So, incorrect statement is option [C].

Here, all the statements are correct. Hence, your answer will be option [D].

Wood, paper, CNG are combustible substances. Substances which easily catch fire are combustible substances. Such as paper, coal, wood etc. Substances which do not catch fire readily are non-combustible substances. Such as sand, water, etc.

In villages, people use wood as fuel because of its easy availability and low cost.

The fire can be extinguished in three ways by; removing of fuel or combustible substances, by removing the heat or by cutting of the supply of oxygen which is present in air.

Here, all the statements are correct. Hence, your answer will be option [D].

Forest fires are not due to cutting of trees.

Respiration is a kind of “slow” combustion of food which takes place in the body to produce heat energy.

The heat and light produced in the sun are not due to ordinary combustion which takes place in the presence of oxygen of air. In the sun, heat and light are produced due to nuclear reactions in which “hydrogen is converted into helium” with the release of heat and light.

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

It is very easy to burn a heap of dry leaves. We know that it is difficult to burn a heap of green leaves. The green leaves contain a lot of water. This water does not allow the green leaves to get heated to their ignition temperature easily and makes the burning of green leaves difficult. On the other hand, dry leaves do not contain water, they get heated to their ignition temperature easily and hence can catch fire easily.

Cover the person with a woollen blanket so that the supply of air to the burning clothes is cutoff and hence, the burning of fire stops.

Here, all the statements are correct. Hence, your answer will be option [D].

The flame extinguishes because of non-availability of oxygen. Air or oxygen is necessary for combustion.

Here, all the statements are correct. Hence, your answer will be option [D].

The spontaneous combustion which take place in nature are very dangerous.

Charcoal is a solid fuel which does not vaporize on heating. So, charcoal does not burn by producing a flame. It only glows on combustion.

It has a high calorific value. Hence, it produces a large amount of heat.

Those substances which do not burn are called non-combustible substance. Some of the non-combustible substances are stone, glass, cement, soil and iron nails etc.

LPG has the highest calorific value i.e. 55,000 kJ/kg. It means that if 1 kg of LPG is burnt completely, then it will produce 55,000 kilojoules of heat energy. Note: Fuel Calorific value Kerosene 45000 kJ/kg Biogas 35000 – 40000 kJ/kg Petrol 45000 kJ/kg.

Wood is a combustible substance. It is a solid fuel and produces smoke during combustion.

Here, all the statements are correct. Hence, your answer will be option [D].