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Hydrocarbons are substances made from carbon and hydrogen only - they make up most of our fuels and so are incredibly important to humans. For example, see this diagram:

An image showing the molecule methane with one central carbon atom and 4 hydrogen atoms branching off it.

Depending on their content of carbon and hydrogen, hydrocarbons burn at different rates. Candles are made from wax, which is a hydrocarbon. Any burning needs oxygen to be present.

Image of a burning candle.

 

A group of pupils researched how long a candle burns for in different volumes of jars when the jar covers the candle. Different volumes provide different amounts of air, i.e. oxygen, and so they burn for different times.

This is the table of their results:

 

 

 Jar volume

Repeat 1 

Time (s)

Repeat 2 

Time (s)

Repeat 3 

Time (s)

 100 ml  6.5  7  13
 200 ml  13  14  13.5
 500 ml  30  34  32
 1000 ml  61  63  63.5

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