AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Students should be able to recall how changing these factors affects the…
Full specification wording
Factors which affect the rates of chemical reactions: Students should be able to recall how changing these factors affects the rate of chemical reactions.
Increasing the concentration of a solution, increasing the pressure of a gas, increasing the surface area of a solid, increasing the temperature, and adding a catalyst all increase the rate of a…
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 2 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Increasing the concentration of a solution, increasing the pressure of a gas, increasing the surface area of a solid, increasing the temperature, and adding a catalyst all increase the rate of a chemical reaction. Conversely, decreasing these factors decreases the rate. You must be able to state these effects clearly. For example, if asked how using a powder instead of a lump affects the rate, you should recall that the powder has a larger surface area and therefore increases the rate. Note that while these factors change the rate, changing concentration, pressure, or temperature can also shift the position of equilibrium in reversible reactions, which affects the yield. The focus here is strictly on recalling the effect on the rate of reaction.
What earns the marks
- Recall that increasing the concentration of reactants in solution increases the rate of reaction.
- Recall that increasing the pressure of reacting gases increases the rate of reaction.
- Recall that increasing the surface area of a solid reactant (e.g., by using a powder) increases the rate of reaction.
- Recall that increasing the temperature increases the rate of reaction.
- Recall that adding a catalyst increases the rate of reaction.
- Recognise that while these factors affect reaction rate, changing temperature, pressure, or concentration can also shift equilibrium and alter yield in reversible reactions.
Common mistakes and how to put them right
Confusing rate with yield.
Put it right by remembering that rate is about how fast the reaction happens, while yield is about how much product is formed.
Stating that a larger lump reacts faster because it has more mass.
Put it right by recalling that a larger lump has less exposed surface area per unit mass, so it reacts more slowly.
Thinking that a catalyst is used up.
Put it right by recalling that a catalyst increases the rate but is not consumed.
Exam tips
- For recall questions, clearly state the direction of change (e.g., 'increases the rate') rather than just saying 'changes the rate'.
- Use comparative language such as 'faster' or 'slower' when comparing two sets of conditions.
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
What happens to the rate of a reaction when the concentration of a reactant in solution is increased?
Listen
Increasing the concentration of a solution, increasing the pressure of a gas, increasing the surface area of a solid, increasing the temperature, and adding a catalyst all increase the rate of a chemical reaction. Conversely, decreasing these factors decreases the rate. You must be able to state these effects clearly. For example, if asked how using a powder instead of a lump affects the rate, you should recall that the powder has a larger surface area and therefore increases the rate. Note that while these factors change the rate, changing concentration, pressure, or temperature can also shift the position of equilibrium in reversible reactions, which affects the yield. The focus here is strictly on recalling the effect on the rate of reaction. A strong answer earns marks for these points. Recall that increasing the concentration of reactants in solution increases the rate of reaction. Recall that increasing the pressure of reacting gases increases the rate of reaction. Recall that increasing the surface area of a solid reactant (e.g., by using a powder) increases the rate of reaction. Recall that increasing the temperature increases the rate of reaction. A common slip: Confusing rate with yield. Instead, remembering that rate is about how fast the reaction happens, while yield is about how much product is formed. Exam tip: For recall questions, clearly state the direction of change (e.g., 'increases the rate') rather than just saying 'changes the rate'.
See it
Key words
Say what each word means before you turn the card.
Rate of reaction
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Catalyst
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Surface area
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Equilibrium
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See every definition
- Rate of reaction
- How fast the reaction happens, rather than how much product is formed.
- Catalyst
- Something that increases the rate of a chemical reaction but is not consumed.
- Surface area
- Increasing this for a solid reactant, for example by using a powder, increases the rate of reaction.
- Equilibrium
- In reversible reactions, changing temperature, pressure, or concentration can shift its position and alter yield.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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