Physical Changes
* Melting: The heat from the flame melts the solid wax, transforming it into a liquid. This is a change in state, but not a change in chemical composition.
* Vaporization: The liquid wax is further heated and vaporized, turning into a gaseous state. Again, this is a change in state, not a chemical change.
* Soot Formation: Incomplete combustion can lead to the formation of soot, a black, carbonaceous solid.
* Change in Shape: The candle itself shrinks in size as the wax is consumed.
Chemical Changes
* Combustion: This is the primary chemical change. The wax reacts with oxygen from the air. The chemical reaction is:
* Wax (Hydrocarbon) + Oxygen → Carbon Dioxide + Water + Heat + Light
* Oxidation: The wax molecules (hydrocarbons) are oxidized, breaking down into simpler molecules. This process releases energy, which we perceive as heat and light.
* Formation of Carbon Dioxide (CO2) and Water (H2O): These are the main products of the complete combustion of wax.
* Formation of Soot (Carbon): As mentioned earlier, incomplete combustion can result in the formation of soot, which is basically pure carbon.
Summary
Burning a candle involves a combination of physical and chemical changes. The wax undergoes physical changes of melting and vaporization, while the chemical reaction of combustion produces carbon dioxide, water, heat, and light. Incomplete combustion can also lead to the formation of soot.
