A student heats iron wool. The iron reacts with oxygen to form solid iron oxide. In trial A, the iron wool is heated in an open dish on a balance. In trial B, the iron wool is heated inside a sealed flask containing enough air for all the iron to react, with the whole flask on a balance. In both trials, the reading is taken before heating and again after cooling. What happens to the reading in each trial?
The reading for trial A does not change, and the reading for trial B increases.
The reading for trial A increases, and the reading for trial B decreases.
The reading for trial A increases, and the reading for trial B also increases.
The reading for trial A increases, and the reading for trial B does not change.
95 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.