AQA GCSE Chemistry Topic 6 - Rate and Extent of Chemical Change - Answers

Sep 5, 2026

GCSE Chemistry Topic 6 focuses on how reaction rate changes with time and conditions, including interpreting rate graphs, explaining the shape of curves, and linking steepness or tangents to reaction rate. It covers practical experiments such as sodium thiosulfate reacting with hydrochloric acid, marble chips producing carbon dioxide, and using apparatus to measure gas volume. It also addresses key ideas like collision theory, concentration and surface area effects, catalysts, and equilibrium, with worked examples and graph-reading methods.

LanguageEnglish

CategoryExam

FormatPDF

Pages4

Reading Time10 min

AccessFree to download

Rate and Extent of Chemical Change

Interpreting rate graphs and tangents

Practical methods for measuring reaction rate

Collision theory, concentration, and surface area

Catalysts and equilibrium

1 AQA GCSE Chemistry Topic 6: Rate and Extent of Chemical Change a Describe in detail what the rate of reaction graph shows. Why does it have this shape? b Describe how sodium thiosulfate can react with HCl ina practical. Write it step by step. 1. | 2. | | --- | | 3. | | 4. | | 5. | i Discuss, in terms of collision theory, what happens toparticles when they are heated. | | | --- | | | | | | When concentration increases explain why rate of reaction increases.
Use diagrams to help you explain.
| j
| | --- | --- | | | | AQA GCSE Chemistry Topic 6: Rate and Extent of Chemical Change a Describe how marble chips and hydrochloric acid can react to produce carbon dioxide. Write it step by step. 1. b How can a balance be used to measure the amount of gas being produced? Choose the correct answer. 1. The quicker the mass lost, the quicker the reaction. 2. The slower the mass lost the quicker the reaction. 3. The quicker the mass is gained the quicker the reaction. c I am feeling confident in the following topics… I need to work on the following topics… | | | --- | | | d Draw a graph of the following results. Add a curve of best fit. | Time | Volume of gas | | --- | --- | | 0 | 0 | | 10 | 11 | | 20 | 16 | | 30 | 19 | | 40 | 21 | Why would you add a tangent to the graph? What does the steepness of the tangent show? | How can a graph be used to calculate the mean reaction rate? Answer the question using the information:
• Work out when the reaction finished;
• Work out how much product formed;
• Divide by the time taken to finish.
The line goes flat at 70s and 80cm3 of gas was produced. Mean rate = | e
| | --- | --- | 2 | Sketch a graph to show a slow reaction.

Sketch a graph to show a quick reaction.
| f
| | --- | --- | Find the mean rate of reaction between these 2 points: g At 30s, 20cm3 of product had been produced and at 60s, 75cm3 had been produced. Mean rate = 1 AQA GCSE Chemistry Topic 6: Rate and Extent of Chemical Change Answers | a
Describe in detail what the rate of reaction graph shows.

The rate of reaction goes quickly to start with and then starts to level off.
Why does it have this shape?
There are more products and less reactants so less reactions occur so the graph starts to level off. | | Complete the formula triangle to show the formula for calculating rates of reaction.
mean rate of reaction = quantity of product formed
time taken

Calculate the rate of reaction when:
The amount of product made is 650g and it takes 50 seconds to produce. Show your working out.
Mean Rate = 650g/50s
Mean rate = 13g/s | c
| Describe how increasing the surface area of a solid reactant affects the rate of reaction.
The rate of reaction is quicker.
e

Why does this happen?
There is more surface area for the reactants to react with so the reaction occurs quicker.
f
Write down the definition of a catalyst.
A catalyst speeds up the rate of a reaction without being used up.
How do catalysts work?
They provide a surface area for the reactants to bind to.

g

What does this symbol show?
A reaction going forwards and backwards. (reversible reaction)
h
What is Le Chatelier’s Principle?
If the conditions are changed in a reversible reaction then the system will counteract that change.
e.g. temperature, pressure, concentration.
| i
Discuss, in terms of collision theory, what happens toparticles when they are heated.

When particles are heated they have more kinetic energy. Particles move around more and more collisions occur.
j

When concentration increases explain why rate of reaction increases.
Use diagrams to help you explain.

There are more particles in the same volume, so collisions are more frequent. | | --- | --- | --- | --- | --- | --- | | | | | | | | | | |

FAQs

How does a rate of reaction graph typically behave over time, and why?

The rate is high at the start and then levels off. As products increase and reactants decrease, fewer successful reactions occur, reducing the rate.

Why does increasing concentration increase reaction rate?

Higher concentration means more particles in the same volume, so collisions are more frequent. More effective collisions lead to a faster rate.

How do catalysts work and what is their effect on reaction rate?

Catalysts speed up the rate of a reaction without being used up. They provide a surface area that helps reactant particles bind and react more effectively.

Sep 5, 2026

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