A student weighs a crucible, adds magnesium, and heats the crucible with its lid raised slightly. The mass of the contents increases. Why is the lid raised slightly during the heating?
To let the magnesium oxide escape from the crucible.
To let the water vapour escape from the hot crucible.
To let the oxygen in the air get into the crucible.
To let the crucible heat up faster over the Bunsen flame.
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.