The Rate and Extent of Chemical Change | AQA GCSE Chemistry, Foundation tier (8462)
The Rate and Extent of Chemical Change
- 96 questions
- 6 subtopics
- Paper 2
- Paper 2
The Rate and Extent of Chemical Change is examined in Chemistry Paper 2.
It covers measuring the mean rate of a reaction, rate from graphs and drawing tangents, factors which affect the rates of chemical reactions, collision theory and activation energy, catalysts and reversible reactions and dynamic equilibrium.
Sample questions from The Rate and Extent of Chemical Change
Answer each one closed book first, then open the answer.
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Measuring the mean rate of a reaction
A reaction uses up 2.4 g of magnesium in 60 s. Calculate the mean rate of reaction.
Show the answer
2.4 g ÷ 60 s = 0.04 g/s. -
Measuring the mean rate of a reaction
A gas is produced at a mean rate of 1.5 cm³/s for 40 s. Calculate the volume of gas collected.
Show the answer
1.5 cm³/s × 40 s = 60 cm³. -
Rate from graphs, and the gradient of a tangent
Two reactions are followed on the same axes of gas volume against time. State how you can tell from the curves which reaction is faster at the start.
Show the answer
The reaction whose curve is steeper at the start is the faster one. -
Rate from graphs, and the gradient of a tangent
What does a straight-line graph that passes through the origin show about the two variables?
Show the answer
The intercept c is zero, so y is directly proportional to x. -
Factors which affect the rates of chemical reactions
State the effect on the rate of reaction of using a powdered solid in place of a single lump of the same mass.
Show the answer
The rate of reaction increases. -
Factors which affect the rates of chemical reactions
Explain how the time taken for a cross to disappear is related to the rate of the reaction.
Show the answer
The rate is proportional to 1 ÷ time, so a shorter time to obscure the cross means a faster reaction. -
Collision theory and activation energy
Explain the two reasons why raising the temperature increases the rate of a reaction.
Show the answer
The particles move faster so they collide more frequently, and a greater proportion of the collisions have at least the activation energy. -
Collision theory and activation energy
What does the symbol ∝ mean?
Show the answer
Is directly proportional to.
The 6 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Measuring the mean rate of a reaction | Following the quantity of reactant used or product formed over time, using a balance for a gas-producing reaction, the mean rate equations, worked calculations, and the units g/s and cm³/s. | 13 |
| Rate from graphs, and the gradient of a tangent | Mean rate calculations, the shape of a volume against time graph and what a horizontal section means, drawing a tangent to find the rate at one moment, comparing rates by steepness and why a curve is steepest at the start, plotting graphs with a line of best fit, y = mx + c, gradients and intercepts of straight lines, and direct proportionality. | 17 |
| Factors which affect the rates of chemical reactions | The five factors that affect rate, the effects of concentration, temperature, surface area, gas pressure and catalysts, investigating concentration by gas volume and by the disappearing cross, why rate is proportional to one over the time taken, identifying variables, and writing a hypothesis. | 15 |
| Collision theory and activation energy | The two conditions for colliding particles to react and activation energy, what collision theory explains, why higher concentration, gas pressure, surface area and temperature make collisions more frequent or more energetic, surface area to volume ratio, predicting rate changes when conditions are altered, and the symbols for proportionality, much less than, much greater than and approximately. | 22 |
| Catalysts | What a catalyst is and why little is needed, why different reactions need different catalysts, enzymes as biological catalysts, how a catalyst provides a pathway with lower activation energy without changing the amount of product or the energy change, its effect on a reaction profile, identifying one, and industrial uses. | 14 |
| Reversible reactions and dynamic equilibrium | Reversible reactions and the ⇌ symbol, forward and reverse reactions and changing direction by altering conditions, heating and rehydrating copper sulfate, equal energy transferred in each direction, the closed system needed for equilibrium, and equilibrium as forward and reverse reactions continuing at the same rate. | 15 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
AQA GCSE Chemistry, Foundation tier Active Recall Guide
Every topic, not just this one. 1,386 questions with their answers.