A burning candle

Watch a candle burn (Activity 5.7). Students guess: the wax melts and evaporates; the wax burns and new substances form; the wick draws up the liquid wax; the wax melts, runs down and sets in new shapes. Who is right?

In a way, all of them. Step by step:

• the heat melts the wax near the wick
• the wick draws up the liquid wax
• the heat turns it into wax vapour
• the vapour burns, and that is the flame
• wax that drips down sets again

Sort the steps:

So a burning candle shows both kinds of change in one process.

Michael Faraday, a great scientist of the 1800s, gave a famous set of lectures called The Chemical History of a Candle. He thought a candle was the perfect object to start studying science, because one small flame shows melting, vapourisation and combustion together.