How does increasing concentration usually increase reaction rate?
Particles move faster, so they collide with more energy
Activation energy is lowered, so more collisions succeed
More particles in the same volume, so they collide more often
More surface area is exposed, so particles collide more often
127 exam-style questions on Edexcel GCSE Chemistry 8.1 Rates of reaction, covering 8.1.1 Measuring and interpreting rates of reaction, 8.1.2 Collision theory and the factors affecting rate, and 8.1.3 Catalysts and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.