CBSE Class 7 Answered

In physical change, when the wick of a candle is lit, the heat of the flame melts the solid wax to liquid wax. It implies that a physical change occurs from solid state to liquid state.

In chemical change, the wax acts as a fuel when the candle is burnt, which is basically carbon. On burning the wick, it produces flame which shows different colours. In the yellow part, carbon combines with oxygen to form carbon dioxide and in the blue part, the hydrogen combines with oxygen to form water and the unburnt carbon is deposited as a black substance called soot. It implies that in a chemical change, carbon gets converted to carbon dioxide and hydrogen is converted to water.