A student does two experiments:
Experiment 1: The student heats 5.00 g of blue copper sulfate crystals in an open crucible. Steam is given off and the crystals turn into a white powder. The mass of the white powder is 3.20 g.
When the student adds a few drops of water to the cooled white powder, it turns blue again and gets hot.
Experiment 2: The student puts 5.00 g of ice in a sealed container and lets it melt. The mass of the liquid water is 5.00 g.
Calculate the percentage of the mass of the blue crystals that is lost in Experiment 1.
Explain why the mass decreases in Experiment 1 but stays the same in Experiment 2.
Ice melting is a physical change. Explain why, in terms of particles.
The student says:
"Heating blue copper sulfate crystals is a physical change, because the change can be reversed by adding water."
Evaluate the student's statement.
48 exam-style questions on OCR GCSE Chemistry 1.1 The particle model, covering 1.1.1 The particle model and changes of state and 1.1.2 Limitations of the particle model. Each one has a worked solution and a mark scheme showing where the marks go.