A student adds a small piece of each of three metals to separate troughs of cold water. The figure shows what the student saw after two minutes.
Figure: Three troughs of cold water, each containing a small piece of a different metal, two minutes after the metal was added

Name the gas given off in the trough containing lithium.
Name the other product formed when lithium reacts with water.
Use the figure to place the three metals in order of reactivity, starting with the most reactive.
The student concludes that copper is the least reactive of all metals. Give one reason why the student cannot be sure of this conclusion.
39 exam-style questions on AQA GCSE Chemistry 4.1 Reactivity of metals, covering 4.1.1 Metal oxides, 4.1.2 The reactivity series, 4.1.3 Extraction of metals and reduction, and 4.1.4 Oxidation and reduction in terms of electrons. Each one has a worked solution and a mark scheme showing where the marks go.