Fire extinguisher

Description:

Use vinegar and sodium bicarbonate to put out some candles. At the end the solution will be much cooler than it started.

Requires:

  • Candles
  • Container or trough
  • Distilled or spirit (not coloured) vinegar
  • Sodium bicarbonate
  • Large jug
Sodium bicarbonate fire extinguisher

Sodium bicarbonate fire extinguisher

Method:

Put lighted candles into the container or trough. If the container is deep use candles at a variety of different heights, if a trough use the smallest candle possible. Put some sodium bicarbonate in the jug and add vinegar. The mixture will fizz and the gas produced can be poured onto the candles. As the gas covers the candles they will go out.

Principle:

This experiment relies on the fact that carbon dioxide extinguishes fire. The carbon dioxide is the gas produced in the reaction between sodium bicarbonate and vinegar (or any other acid).
The cooling of the solution in the jug is because this is an example of an endothermic reaction.

Tips:

The demonstration can be made more impressive if the jug is used to fill an intermediate (transparent) container with carbon dioxide. That is unlikely to work outdoors or where there is a lot of air movement from ventilation or air-conditioning systems though.

Practise is called for in order to get the desired effect of the lower candle being extinguished first. Often the stream of carbon dioxide puts out the taller candle which diminishes the effect.

Safety:

Do not leave candle flames unattended. Ensure that the candle is mounted on a stable base.

Tags: decomposition, endothermic, carbon dioxide, carbonate, density.