Factors which affect the rates of chemical reactions: Students should be able to recall how changing these factors affects the rate of chemical reactions.

Q: How do I revise Factors which affect the rates of chemical reactions: Students should be able to recall how changing these factors affects the rate of chemical reactions. for GCSE?

Read the notes on Factors which affect the rates of chemical reactions: Students should be able to recall how changing these factors affects the rate of chemical reactions., then test yourself without looking. Answering questions and checking what you missed builds recall faster than re-reading.

Q: Is this Factors which affect the rates of chemical reactions: Students should be able to recall how changing these factors affects the rate of chemical reactions. guide aligned to the AQA specification?

Yes. This guide is linked to the Factors which affect the rates of chemical reactions: Students should be able to recall how changing these factors affects the rate of chemical reactions. topic in the AQA GCSE specification.

The rate of a chemical reaction is the speed at which reactants are used up or products are formed.

Study notes

From the checked teaching notes for this specification point.

The idea

What earns the marks

State that increasing temperature increases rate because particles gain kinetic energy, move faster and collide more frequently and with greater energy.
State that increasing concentration or pressure increases rate because particles are closer together, so collision frequency increases.
State that increasing surface area of a solid increases rate because more reactant particles are exposed and available to collide.
State that a catalyst increases rate by providing an alternative reaction pathway of lower activation energy, and is not used up.
Link each factor to collision frequency or collision energy, not merely to 'more reactions happening'.
Use correct units where relevant, such as mol/dm³ for concentration and °C or K for temperature.

Common mistakes and how to put them right

Saying a catalyst increases the rate by increasing collision frequency.
Put it right: A catalyst lowers activation energy by providing an alternative pathway, so more collisions are successful.
Confusing surface area with concentration.
Put it right: Surface area applies to solids, while concentration applies to solutions and pressure to gases.
Stating that increasing temperature makes particles bigger or increases their volume.
Put it right: It increases their kinetic energy and speed, so collisions are more frequent and energetic.

Exam tips

For each factor, write a cause-and-effect chain: change → particle behaviour → collision frequency or energy → rate.
Use comparative language such as 'faster', 'more frequent' and 'greater energy' rather than vague words like 'better'.
When asked to explain, refer to particles and collisions; when asked to state, a short accurate sentence is enough.

Try the lesson

The start of the Factors which affect the rates of chemical reactions: Students should be able to recall how changing these factors affects the rate of chemical reactions. lesson, made from checked teaching notes for this specification point.

Have a go first

A student adds marble chips to dilute hydrochloric acid. The reaction produces carbon dioxide gas. Which change would increase the rate of this reaction?

Tip: press 1 to 4 to choose

Listen

The rate of a chemical reaction is the speed at which reactants are used up or products are formed. It increases when particles collide more frequently or with greater energy. Raising temperature makes particles move faster, so collisions are more frequent and more energetic; this increases rate. Increasing concentration of a solution, or pressure of a gas, packs particles closer, increasing collision frequency. Increasing surface area of a solid exposes more particles to collision. A catalyst provides an alternative pathway with lower activation energy, increasing rate without being used up. For example, magnesium ribbon reacts faster with 2 mol/dm³ hydrochloric acid than with 1 mol/dm³ acid, and faster still if the acid is warmed. Powdered calcium carbonate fizzes faster than the same mass of lumps in acid. A strong answer earns marks for these points. State that increasing temperature increases rate because particles gain kinetic energy, move faster and collide more frequently and with greater energy. State that increasing concentration or pressure increases rate because particles are closer together, so collision frequency increases. State that increasing surface area of a solid increases rate because more reactant particles are exposed and available to collide. State that a catalyst increases rate by providing an alternative reaction pathway of lower activation energy, and is not used up. A common slip: Saying a catalyst increases the rate by increasing collision frequency. Instead, a catalyst lowers activation energy by providing an alternative pathway, so more collisions are successful. Exam tip: For each factor, write a cause-and-effect chain: change → particle behaviour → collision frequency or energy → rate.

See it

A top-down flowchart. A single starting node, 'Change a factor', branches into four factors: 'Temperature increased', 'Concentration or pressure increased', 'Surface area of a solid increased' and 'Catalyst added'. Each factor leads to its own explanation node. Temperature leads to 'Particles move faster: collisions more frequent and more energetic'. Concentration or pressure leads to 'Particles packed closer: collision frequency increases'. Surface area leads to 'More particles exposed: available to collide'. Catalyst leads to 'Alternative pathway with lower activation energy'. All four explanation nodes then lead to a single final node, 'Rate increases'. — It shows how each factor changes particle behaviour and collisions, leading to an increased rate of reaction.

Label the diagram

Some boxes have lost their names. Pick the right name for each number.

The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. A single starting node, 'Change a factor', branches into four factors: 'Temperature increased', 'Concentration or pressure increased', 'Surface area of a solid increased' and 'Catalyst added'. Each factor leads to its own explanation node. Temperature leads to 'Particles move faster: collisions more frequent and more energetic'. Concentration or pressure leads to 'Particles packed closer: collision frequency increases'. Surface area leads to 'More particles exposed: available to collide'. Catalyst leads to 'Alternative pathway with lower activation energy'. All four explanation nodes then lead to a single final node, 'Rate increases'.

1Box 1
2Box 2
3Box 3

0 of 3 labelled

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