Pearson International GCSE Chemistry 1: Principles of Chemistry
Pearson International GCSE Chemistry notes on particles, atoms, bonding, formulae, equations and calculations.
The principles topic supplies the particle, atomic, bonding and quantitative language used throughout 4CH1. It is not a single isolated chapter: later questions on rates, equilibrium, acids, metals and organic chemistry assume that these foundations are secure.
The official specification separates statements that all candidates study from additional bold content assessed through Paper 2. Check your centre's entry route before deciding that a subtopic can be omitted.
Particle ideas and separation
In a solid, particles vibrate about fixed positions. In a liquid, particles remain close but move past one another. In a gas, particles are much farther apart and move rapidly in random directions. Heating increases their average kinetic energy; it does not make the particles themselves larger.
Changes of state are physical changes because no new substance forms. During melting or boiling, transferred energy overcomes attractions between particles. The temperature remains constant during a pure substance's change of state because the energy is changing particle arrangement rather than increasing average kinetic energy.
Choose a separation method from the property that differs:
| Mixture | Useful difference | Suitable method |
| Insoluble solid and liquid | Particle size and insolubility | Filtration |
| Dissolved solid and solvent | Volatility | Crystallisation or simple distillation |
| Two miscible liquids | Boiling temperature | Fractional distillation |
| Coloured soluble substances | Attraction to phases and solubility |
Check this topic from memory
Attempt the matching topic bank before reopening the notes. Use each missed idea to decide what to review next.
Start the topic quiz
