Particle model of matter
Particle model of matter

Every substance is made of particles that are always moving. In a solid, particles are very close together in a regular arrangement and vibrate about fixed positions.
Step-by-step lessons on Edexcel GCSE Chemistry 3.1 States of matter, covering 3.1.1 The three states of matter and changes of state. Each one builds up to exam-style questions. Nail the core quantitative topics — moles, balancing equations and calculations — early on, since they underpin higher-tier questions across every paper and topic.