A piece of copper is heated inside a sealed glass tube containing air. The mass of the copper increases by 0.20 g. What happens to the total mass of the sealed tube and its contents?
It increases by 0.20 g0.20\ \text{g}0.20 g, the same as the copper.
It does not change from its starting value.
It decreases by 0.20 g0.20\ \text{g}0.20 g, because oxygen is used up.
It increases by 0.40 g0.40\ \text{g}0.40 g, twice the gain of the copper.
40 exam-style questions on AQA GCSE Chemistry 3.1 Chemical measurements, conservation of mass and the quantitative interpretation of chemical equations, covering 3.1.1 Conservation of mass and balanced chemical equations, 3.1.2 Relative formula mass, 3.1.3 Mass changes when a reactant or product is a gas, and 3.1.4 Chemical measurements. Each one has a worked solution and a mark scheme showing where the marks go.