Final answer:
Magnesium reacts with oxygen to produce a bright white flame, heat, and magnesium oxide as a white powder, following the balanced equation 2Mg + O₂ → 2MgO, demonstrating both a combination reaction and the conservation of mass.
Step-by-step explanation:
The evidence of a chemical reaction between Mg (magnesium) and oxygen includes the production of a bright white flame, the evolution of heat, and the transformation of the shiny metallic magnesium into a crumbly white powder of magnesium oxide (MgO). The reaction can be represented by the balanced chemical equation: 2Mg (s) + O₂(g) → 2MgO (s). This process exemplifies a combination reaction where magnesium is oxidized, losing electrons, and oxygen is reduced, gaining electrons. Additionally, the law of conservation of mass applies as the mass of the products equals the mass of the reactants, with no change in total mass.
This change in mass is consistent with the law of conservation of mass, providing further proof of a chemical reaction occurring between magnesium and oxygen.