Monday, December 28, 2009

[Science Form 1] Oxygen Is Needed For A Fire To Burn

There are many experiments that you can do to show that oxygen is needed for a fire to burn. Let's take a look at one of these experiments.

  1. A candle is lighted, and when it is burning well, a glass jar (like a jelly jar) is inverted over the candle.
  2. The water level is immediately marked.
  3. After the candle stops burning, the water level is marked again.
  4. The amount of air required for the candle to burn is calculated using the following formula:

When the burning candle is completely extinguished, water rises up and fills one-fifth (1/5) of the original volume of air in the glass jar.

The glass that supports the burning of the candle makes up about one-fifth of the composition of air in the glass jar.

Since the oxygen makes up one-fifth of the volume of air, it can be concluded that oxygen is used in the combustion of the candle.

  • The cork base keeps the candle afloat.
  • The glass jar contains nitrogen, carbon dioxide and water vapour.
  • When the candle completely burns out, water in the jar rises.
  • The height of air in the column is used to calculate the amount of air used.
  • The candle stops burning because all the oxygen in the jar has been used.
  • Oxygen supports the combustion of the candle.

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