Question

Air contains oxygen and nitrogen. How will you prove it?

Answer 1

Take a glass vessel and fix a candle at its centre. Now, fill half the glass vessel with water and place an inverted gas jar over the candle. Note the water level. Remove the gas jar and light the candle, and again cover it with the former. After some time, the candle will extinguish and the level of water in the gas jar will rise up. As all the oxygen in the jar was consumed, the candle stopped burning, and the place occupied by this gas became empty, thereby raising the level of water in the jar. Now, remove the gas jar by keeping its mouth tightly closed, and introduce a burning splinter into it. The splinter will get extinguished. This shows that the remaining air in the jar does not support burning. This gas is nitrogen.
This activity proves that air contains oxygen and nitrogen.