A student heats magnesium ribbon in an open crucible. The magnesium burns to form magnesium oxide.
The mass of the solid in the crucible increases.
Which statement explains why the mass increases?
Magnesium atoms get heavier when they are heated.
Heat energy transferred to the magnesium has mass.
New magnesium atoms are made during the reaction.
Oxygen from the air combines with the magnesium.
55 exam-style questions on OCR GCSE Chemistry 3.1 Introducing chemical reactions, covering 3.1.1 Writing formulae and balanced chemical equations, 3.1.2 Formulae of compounds from ions, and state symbols, 3.1.3 Conservation of mass and observed changes in mass, 3.1.4 Half equations and balanced ionic equations, 3.1.5 The mole and the Avogadro constant, and 3.1.6 Stoichiometry, limiting reactants and reacting masses. Each one has a worked solution and a mark scheme showing where the marks go.