Question

Why is the melting of wax a physical change while the burning of a candle is a chemical change?

Answer 1

• Neither liquid wax nor solid wax burn. It is only the wax vapors that burn.
• When a candle wick is lit, the heat produced from the flame melts the wax [Melting-physical change].
• The wick soaks or absorbs the molten wax. The heat of the flame vaporizes the molten wax in the wick [Vaporization-physical change].
• The gaseous wax burns in the flame, which keeps the flame alive. This process goes on till the entire wax gets burnt [Burning- Chemical change].

Physical Changes: A change that alters some specific physical property of the matter, like its state, texture, magnetic or electrical conditions, or color, without causing any change in the composition of its molecules, is called physical change, provided it gets reversed, if the cause producing the change is removed.

Chemical Changes: A change that alters the specific properties of a material by bringing about a change in its molecular composition, followed by a change in state, is called a chemical change.

So, the melting of wax is a physical change while the burning of a candle is a chemical change.