Which event always involves a chemical change ?

In my own words, this summary equation tells me that:

When glucose reacts with oxygen, carbon (IV) oxide and water are given off and energy is produced.

Explanation:

Cellular respiration is known to be a metabolic reaction which actually occur in the cells of living organisms whereby chemical energy is converted into energy (ATP) and certain waste products, carbon (IV) oxide and water are released. We can simply put that cellular respiration is a process of converting sugars to energy. In the giving equation, we can see that glucose which is a sugar reacts with oxygen to give CO₂ and H₂O.