Pearson Edexcel International GCSE in Chemistry · 4CH1
Topic 3 · Physical chemistry
Why reactions release or absorb energy, what controls how fast they go, and what happens when a reaction can run both ways and settles into equilibrium.
8 lessons, covering 22 specification statements: 3.1 · 3.2 · 3.8 · 3.3 · 3.4 · 3.5 · 3.6 · 3.7 · 3.9 · 3.10 · 3.15 · 3.11 · 3.14 · 3.12 · 3.13 · 3.16 · 3.17 · 3.18 · 3.19 · 3.20 · 3.21 · 3.22
The lessons
- Exothermic and Endothermic Reactions — Reactions that warm their surroundings and reactions that chill them — and why the thermometer tells you which. (3.1, 3.2, 3.8)
- Calorimetry Calculations — Turning a temperature rise into an energy in joules, and then into a value per mole. (3.3, 3.4)
- Energy Diagrams and Bond Energies — Why breaking bonds costs energy, why making them repays it, and why the balance decides everything. (3.5, 3.6, 3.7)
- Rates of Reaction — Four things that make a reaction faster, and two ways of measuring whether they did. (3.9, 3.10, 3.15)
- Collision Theory — One explanation that accounts for every factor on the previous page. (3.11, 3.14)
- Catalysts — A substance that speeds a reaction up, takes part in it, and is there unchanged at the end. (3.12, 3.13, 3.16)
- Reversible Reactions — Reactions that run both ways, and two you can drive backwards and forwards at will. (3.17, 3.18)
- Dynamic Equilibrium — Nothing appears to be happening, everything is still happening — and that is what lets conditions shift it. (3.19, 3.20, 3.21, 3.22)