A student puts 2.0 g of iodine crystals into a glass tube and seals the tube.
The total mass of the sealed tube and the iodine is 45.6 g.
She warms the tube gently. The solid iodine turns straight into a purple gas, and no liquid forms.
Name this change of state.
State the total mass of the sealed tube when all of the iodine is a gas. Explain your answer.
The tube is cooled. Shiny iodine crystals form again on the inside of the glass.
Explain how this shows that the change in (a) is a physical change.
Another student boils 150 g of water in an open beaker for 10 minutes. At the end, the mass of the water in the beaker is 128 g.
The student says:
'This shows that mass is not conserved when water boils.'
Explain why the student is wrong.
44 exam-style questions on OCR GCSE Physics 1.2 Changes of state, covering 1.2.1 Conservation of mass during changes of state, 1.2.2 Physical and chemical changes, 1.2.3 Heating, temperature and changes of state, 1.2.4 Specific heat capacity and specific latent heat, 1.2.5 Internal energy and temperature change, and 1.2.6 Energy transfer during a change of state. Each one has a worked solution and a mark scheme showing where the marks go.