Particle model and mass conservation
Particle model and mass conservation
A change of state happens when a substance moves between solid, liquid and gas without becoming a new substance. In the particle model, solids have particles close together in a regular arrangement, liquids have close but random particles, and gases have particles far apart and moving freely.
Step-by-step lessons covering OCR GCSE Physics Changes of state for Foundation and Higher tier. Each lesson works through exam-style questions in Paper 1 and Paper 2 (Foundation Tier) or Paper 3 and Paper 4 (Higher Tier) format. Paper 2 and Paper 4 include synoptic questions that draw on Topics P1–P4, so revisit earlier topics before final exams rather than treating each paper as self-contained.
