There are two changes in wax combustion, the first is physical change: solid wax is liquefied by heating, and then vaporized into waxy gas molecules dispersed in the air; Then there is chemical change: gaseous wax molecules mix with oxygen to produce redox reaction, and CO2 and water are generated.
The main component of candles is carbon and oxygen compounds, which react with oxygen in the air when burning to produce water and carbon dioxide.
When observing the whole process of candle burning, scientists found that the mass of water and carbon dioxide produced by candle burning is exactly equal to the sum of the mass of candle and the mass of oxygen consumed by candle burning.