Heating sugar with candles will change physically and chemically. The burning time of the candle will be shorter and shorter, and the candle oil will flow out to cool on the surface of the candle, changing the shape of the candle. These are the physical changes of candles. Candles emit light and heat, which change from hydrocarbons to substances such as carbon dioxide and water, and undergo chemical changes. Sugar also undergoes physical changes. The temperature of sugar will rise, its viscosity will become stronger and its shape will change. These are all physiological changes. If the temperature is higher, the sugar will zoom and smoke, which is a chemical change.