Two colourless liquids are mixed and bubbles appear. Analysis shows that the bubbles contain substance Z, which was not present in either liquid. Why is this evidence of a chemical change?
Every change that produces bubbles is chemical
Gas particles always have a different identity from liquid particles
A new substance, Z, has formed
The particles in the liquids have stopped moving
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.