Explain why the mass of a metal oxide may be greater than the mass of the metal when oxygen reacts with the metal.

In the subtopic Mass changes when a reactant or product is a gas, this learning objective focuses on explain why the mass of a metal oxide may be greater than the mass of the metal when oxygen reacts with the metal. It sits within Chemical measurements, conservation of mass and the quantitative interpretation of chemical equations for AQA GCSE Chemistry 8462 Unit 4.3, so the explanation must stay anchored to quantitative chemistry rather than drifting into a general chemistry idea. Approved keywords to use include metal oxide. Metal oxide. means a compound formed when a metal reacts with oxygen, resulting in a product that may have a greater mass than the original metal Avoid the mistake of students often think that the mass of a metal oxide is greater than the mass of the metal because the metal gains weight during the reaction; instead, explain that the increase in mass is due to the oxygen from the air combining with the metal, which adds to the total mass of the product For exam answers, when studying reactions involving metals and oxygen, remember that the mass of the metal oxide can be greater than the mass of the metal due to the addition of oxygen