Practical questions
You will complete eight required core practical activities if you are studying GCSE Chemistry, and 18 if you are studying GCSE Combined Science (five of these are in Chemistry).
You could be asked questions about the apparatus, methods, safety precautions, results, analysis and evaluation of these experiments.
There are two core practical activities in the Rates of reaction and energy changes section:
- investigating the effects of changing the conditions of a reaction on the rates of chemical reactions by measuring the production of a gas
- investigating the effects of changing the conditions of a reaction on the rates of chemical reactions by observing a colour change.
Edexcel questions courtesy of Pearson Education Ltd.
Learn about practicals with Dr Alex Lathbridge
Listen to the full series on BBC Sounds.
Dr Alex Lathbridge answers questions about practicals.
Sample question 1 - Foundation
Question
A student carries out an experiment to measure accurately the temperature changes when different metals are added to iron(II) sulfate solution.
The method for the experiment is:
- measure 25 cm3 of iron(II) sulfate solution and pour into a container
- record the initial temperature of the solution
- add excess magnesium ribbon
- record the highest temperature of the mixture
- repeat the experiment using excess copper turnings, then using excess zinc foil
a) State a suitable container for the iron(II) sulfate solution in this experiment. [1 mark]
b) State what the student should do to the mixtures during the experiment. [1 mark]
c) Explain how the student could improve the method to make a fairer comparison of the temperature change produced by the different metals. [2 marks]
a) Any one from:
- beaker
- polystyrene cup
- conical flask
[1]
b) Stir the mixtures with the thermometer [1]
c) Improvement with reason, eg:
- use magnesium, zinc and copper as powders [1]
- so they have the same/similar size particles/surface area/shape [1]
Sample question 2 - Foundation
Question
Sodium thiosulfate solution, Na2S2O3, reacts with dilute hydrochloric acid:
Na2S2O3(aq) + 2HCl(aq) → 2NaCl(s) + H2O(l) + S(s) + SO2(g)
The rate of this reaction can be investigated by mixing the reactants and finding the time taken for a precipitate of sulfur to become visible.
A student wants to investigate the effect of changing the temperature on the rate of this reaction.
Devise a method the student could use to find out how the time taken for the precipitate of sulfur to become visible changes with temperature. [3 marks]
- suitable method of warming the solutions, eg water bath, Bunsen burner with tripod and gauze, and measure the temperature of each solution using a thermometer [1]
- use the same volumes of the solutions in each experiment [1]
- measure the time for the precipitate to form (and hide a cross) [1]
Sample question 3 - Higher
Question
Two gases, X and Y, react to give a gaseous product Z.
The reaction is carried out under two different sets of conditions in experiments 1 and 2 as shown in the table.
| Condition | Experiment 1 | Experiment 2 |
| Temperature (°C) | 30 | 20 |
| Pressure (atm) | 1 | 2 |
| Condition | Temperature (°C) |
|---|---|
| Experiment 1 | 30 |
| Experiment 2 | 20 |
| Condition | Pressure (atm) |
|---|---|
| Experiment 1 | 1 |
| Experiment 2 | 2 |
Explain why it is not possible to predict what the rate of Experiment 2 will be compared with Experiment 1.
[3 marks]
- the decrease in temperature will cause a decrease in rate of reaction [1]
- the increase in pressure will cause an increase in rate of reaction [1]
- because the changes have opposite effects on the rate it is not possible which has the greater effect [1]
Sample question 4 - Higher
Question
When sodium hydroxide solution is neutralised with an acid there is a temperature change.
A student is given dilute hydrochloric acid and dilute ethanoic acid of the same concentration in mol dm-3.
Devise a plan to compare the temperature changes produced when sodium hydroxide solution is neutralised with each of these two acids. [4 marks]
- measure known volume of sodium hydroxide solution [1]
- add same volume of each of the acids [1]
- stir the mixture [1]
- record the initial and final temperatures/the temperature change [1]
