Final answer:
Oxygen and wax react with each other when a candle burns, undergoing a combustion reaction that produces carbon dioxide and water vapor alongside light and heat.
Step-by-step explanation:
When a candle burns, the two substances that react with each other are oxygen and wax. This reaction is an example of a combustion reaction, a type of chemical reaction where a substance combines with oxygen, releasing energy in the form of light and heat. The wax in a candle, which is a high-molecular-mass hydrocarbon, reacts with oxygen to produce gaseous carbon dioxide and water vapor. The overall chemical equation representing this reaction is:
Candle wax (hydrocarbon) + O₂ (g) → CO₂ (g) + H₂O(g)
This process is exothermic, meaning it releases energy. Evidence of a chemical change includes the production of light and heat, and the formation of new substances with different properties, specifically water vapor and carbon dioxide in this case.