Combustion

Question 1 Define the term combustion?

Question 2 What are fuels. Name 2 fuels?

Question 3 What are combustible substances. Give example?

Question 4 What are non-combustible substances. Give example?

Question 5 Can the process of rusting of iron be called combustion. Give reason for answer?

Question 6 What happens when combustion of magnesium takes place?

Question 7 What happens when combustion of charcoal take place?

Question 8 Respiration is a slow combustion. Explain?

Combustion

A chemical process in which a substance reacts with the oxygen to give heat and light is called combustion.

The light which is given off during combustion can be in the form of flame or as a glow.

The substance which undergoes combustion is said to be combustible. It is called fuel.

1) Combustion of Magnesium

If a magnesium ribbon is heated, it starts burning. When a magnesium ribbon burns, it combines with the oxygen of air to form magnesium oxide and liberates heat and light.

Magnesium + Oxygen → Magnesium oxide + heat +Light

The burning of magnesium in air to produce heat and light is a combustion process. Magnesium is a combustible substance.

2) Combustion of Charcoal

When charcoal burns, then the carbon of charcoal combines with the oxygen of air to form carbon dioxide. A lot of heat is produced in the combustion reaction but only a little light is produced.

Carbon + oxygen → Carbon dioxide + heat +light
(Charcoal)

Oxygen is necessary for combustion to take place. It is a supporter of combustion.

Food is a fuel for our body. During respiration, the digested food is broken down by the reaction with oxygen in the body cells to produce carbon dioxide, water and heat energy. This heat energy is utilised by our body. Respiration is a kind of slow combustion of food which take place in the body to produce heat energy.

The rust is formed when iron slowly combines with the oxygen present in air to form iron oxide. The process of rusting of iron is an example of slow combustion.

The sun produce heat and light. In the sun, heat and light are produced due to nuclear reactions.

Combustible substances

Those substances which can burn are called combustible substances.

For Example : Cloth, straw, cooking gas, kerosene oil, wood, coal, charcoal etc.

A combustible substance is called as fuel.

Non-combustible substances

Those substances which do not burn are called non-combustible substances.

For Example : Stone, cement, glass, bricks, soil, sand, water, iron nails, copper objects.