Changes when a candle burns

This week the Year 5 and 6 classes found out that there are many changes that occur when a candle burns.

So what is produced when a candle burns?

• You sometimes get smoke and soot (which is particles of partly burnt wax)
  
• The wax changes into melted wax.
• Carbon Dioxide and Water are produced from the chemical reaction between the oxygen and the fuel in the flame.

These photos show how we collected soot from the burning candle. We held the tinfoil above the flame, in the top of the flame and near the bottom of the flame.

Miss Harrison challenged us to think about whether these changes were reversible or irreversible (permanent).

This is what we came up with.

Reversible Changes
The only reversible change is the melted wax. When you let the melted wax cool down it turns back into solid wax. You could reshape this wax into a new candle.

Irreversible Changes
The main irreversible change is the water and carbon dioxide. This was formed from the chemical reaction between the fuel and the oxygen and you can't change them back.