Some iodine crystals are heated in a sealed tube. The crystals turn directly into a purple gas.
When the tube cools, grey iodine crystals form again at the cool end of the tube. The crystals have the same properties as before.
Which statement describes these changes?
A chemical change, then a physical change back to iodine
Two physical changes, as the iodine recovers its properties
Two chemical changes, as a purple substance is made and lost
A physical change, then a chemical change that makes crystals
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.