Chemistry - PPE 3
What is rate of reaction?
The speed at which reactants are converted into products.
Equation for rate of reaction (gas volume method)?
Rate = volume of gas ÷ time
Equation for rate of reaction (mass method)?
Rate = change in mass ÷ time
How does temperature affect rate?
Increases particle kinetic energy → more frequent successful collisions.
Why does higher temperature increase successful collisions?
More particles have energy ≥ activation energy.
How does concentration affect rate?
Higher concentration = more particles per volume = more collisions.
How does pressure affect gas reactions?
Higher pressure = particles closer together = more collisions.
How does surface area affect rate?
Larger surface area = more exposed particles = more collisions.
What is a catalyst?
A substance that speeds up a reaction without being used up.
How do catalysts work?
Provide an alternative pathway with lower activation energy.
What is activation energy?
Minimum energy particles must have to react.
What is collision theory?
Particles must collide with enough energy and correct orientation to react.
How is rate measured experimentally?
Gas volume, mass loss, colour change, or precipitate formation.
Why does rate decrease during a reaction?
Reactants are used up → fewer successful collisions.
Required practical for rates?
Investigating effect of concentration on rate using sodium thiosulfate.