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4.6 The rate and extent of chemical change

3 dot points across 3 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

What factors change the rate of a reaction, and why?

Collision theory; the effects of concentration, pressure, surface area, temperature and catalysts on rate; and how catalysts work.
A focused answer to AQA GCSE Chemistry 4.6.1, covering collision theory and how concentration, pressure, surface area, temperature and catalysts change the rate of a reaction, and how catalysts provide a lower-activation-energy pathway.
9 min answer →

What is the rate of a reaction, and how do we measure it?

The rate of reaction; how to measure rate by following mass loss or gas volume; calculating mean rate; and finding the rate at a point from a tangent on a graph.
A focused answer to AQA GCSE Chemistry 4.6.1, covering what the rate of a reaction means, methods for measuring it by mass loss or gas volume, calculating the mean rate, and finding the rate at a particular time from the gradient of a graph.
9 min answer →

What are reversible reactions, and how does equilibrium respond to change?

Reversible reactions; dynamic equilibrium in a closed system; the energy changes of reversible reactions; and Le Chatelier's principle for changes in concentration, temperature and pressure.
A focused answer to AQA GCSE Chemistry 4.6.2, covering reversible reactions, dynamic equilibrium in a closed system, the opposite energy changes of the forward and backward reactions, and Le Chatelier's principle for changes in concentration, temperature and pressure.
9 min answer →