Fire extinguisher

Light a candle stump in an empty glass, and mix in another glass as in the previous experiment a teaspoonful of bicarbonate of soda with some vinegar and let it froth. If you tilt the glass over the candle, the flame goes out.
The carbon dioxide formed in the chemical reaction in the top glass displaces the air needed for the flame, because It is heavier, and because it is non combustible the flame is smothered. Many fire extinguishers work in the same way the sprayed foam consists of bubbles filled with carbon dioxide. It surrounds the flame and blocks the supply of oxygen.