* New substances are formed: When magnesium burns, it reacts with oxygen in the air to form magnesium oxide (MgO). This is a completely different substance from the original magnesium metal.
* Energy is released: Burning is an exothermic reaction, meaning it releases heat and light.
* The change is irreversible: You can't easily turn magnesium oxide back into magnesium metal and oxygen.
These are all characteristics of a chemical change, indicating that the chemical composition of the magnesium has been altered.
