Sharon Endebak

Fire Extinguisher

Science Concept: Density

Mixing baking soda and vinegar produces carbon dioxide gas.

Materials:

600 mL beaker

1 candle about 3 inches in height (also could use a 2nd shorter candle)

baking soda

lighter or matches

vinegar

40 mL beaker

Directions:

1. Place the candle upright in the 400 mL beaker.

2. Measure four grams of baking soda.

3. Measure 30 mL of vinegar in the 40 mL beaker.

4. Pour the baking soda in the bottom of the 600 mL beaker.

5. Slowly pour the vinegar into the 600 mL beaker with the baking soda.

Introduction:

How many of you would like to be a Fireman when you grow up? Well, today I am a firefighter, and I can show you some tricks.

Explanation:

Fire needs oxygen so in thhis demo, you can see the candle burning normally in air in the presence of oxygen.

The combustion reacion is:
wax + oxygen in the air ---> carbon dioxide + water

C₂₂H₄₄ + 33 O₂ ---> 22 CO₂ + 22 H₂O + heat energy

When the baking soda and vinegar combine, they form carbon dioxide gas. Carbon dioxide is more dense than air, so therefore it fills the bottom of the beaker first. The carbon dioxide slowly rises to the top of the beaker, forcing the air with oxygen out of the beaker. Since there is a lack of oxygen, the flame is extinguished.

vinegar + baking soda ---> sodium acetate + carbon dioxide gas + water
acetic acid + sodium bicarbonate

HC₂H₃O₂ + NaHCO₃---> NaC₂H₃O₂ + CO₂ + H₂O

Safety:

Caution should always be taken when a flame is involved. However, there are no harmful chemicals involved, so glasses need not be worn.

Disposal:

The baking soda and vinegar can be disposed of in the sink.

Reference: Adapted from: Bilash II, B, Gross, G, Koob, J, A Demo A Day, Flinn Scientific, 1995, p. 12