A student investigates different laboratory processes. Which of the following processes describes a chemical change?
Melting solid paraffin wax by heating it gently in a beaker.
Heating a piece of clean copper foil in a Bunsen burner flame until a black layer forms on its surface.
Separating a mixture of ethanol and water using fractional distillation.
The condensation of water vapour on a cold window pane to form liquid water droplets.
55 exam-style questions on OCR GCSE Chemistry Introducing chemical reactions. Each one has a worked solution and a mark scheme showing where the marks go.