combines with oxygen to form carbon dioxide water and energy.

Form similar pair of words.

Nitrogen and _____ / oxygen and $21\%$.

Explain the practical uses of ${\mathrm{CO}}_2$.

Explain the composition of air with the help of a diagram.

Give reasons for the following.

In (a) the candle continues to burn.

In (b) the candle is put out.

If we cut off the supply of air for combustion of a substance, what will happen?

Explain, use of ${\mathrm{CO}}_2$ in fire extinguisher.

What does air contain?

If the supply of oxygen is not sufficient, will the fuels burn completely?

Air has various gases in different proportion. What is the ratio of ${\mathrm{CO}}_2$ in atmosphere?

With the help of an experiment, show that air is necessary for burning of a candle.