A Burning Problem...

Joke: What do you call a well-known candle? FLAMOUS!

What happens when something is on fire? How does a fire extinguisher do it's job? Get an adult to help you set up this little demonstration...

Whenever we burn something, we are adding oxygen. Lets say we burn a piece of coal. Coal is almost pure Carbon, a non-metal. Burning is a chemical reaction that joins the carbon to oxygen in the surrounding air to form (among other things) Carbon Dioxide.

Understanding how burning occurs is important because all we need to do then to put out a fire is to get rid of the oxygen to stop it joining with the carbon!

One way is to use a fire extinguisher. Fire extinguishers work by removing one of the critical ingredients for a fire - oxygen. Lets demonstrate...

  • Fill a small dish with baking soda.
  • Place a short candle and a slightly longer candle upright in the baking soda
  • Place the dish into the bottom of a large bowl.
  • Have an adult light both candles (CARE: never use matches without an adults permission!)

Now lets have some fun!

Pour some vinegar into the dish of baking soda (not on the candles!).

  • PREDICT: Ask your students "What will happen to the candles?"
  • OBSERVE: Watch what happens as the candles burn and the baking soda fizzes. You may have to add a little more vinegar to keep the fizzing going.
  • EXPLAIN: What does this show us? (seniors might like to consider the chemical reaction at work and ways to identify the gas given off)


The vinegar acts as an acid and reacts with baking soda, producing carbon dioxide gas. The carbon dioxide gas is heavier than the surrounding air so it sinks into the bottom of the bowl.

As the reaction continues, more and more carbon dioxide gas is produced which begins to slowly fill up the bowl. When the level of carbon dioxide has risen to the level of the flame, the flame will go out from lack of oxygen.

If you find yourself on fire, you are told to STOP, DROP and ROLL. This helps put out the flames because by lying on the flaming clothes you are smothering the fire, preventing oxygen in the air getting to it.

Carbon dioxide is a colourless, odourless gas. It occurs in the atmospheres of many planets, including that of the Earth. On the Earth, all green plants must get carbon dioxide from the atmosphere to live and grow. Carbon dioxide is also created by the burning of any substance that contains carbon, eg, coal, gasoline, and wood. Carbon dioxide makes up less than 1 per cent of the earth's atmosphere. It is also the gas in fizzy drinks that makes the bubbles. It also makes the drinks slightly acid!


  1. What different types of fire extinguisher are there?
  2. What do you do in your home when a fire breaks out?
  3. Where is your smoke alarm located and how does it work?
  4. The interactive pages...identify these pieces of lab equipment
  5. The interactive pages...weird metals and gases hide in this Periodic Table

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