Chemistry required practicals

Temperature changes in reactions

AQA 4.5 · RP4

GCSE Chemistry (8462) · Required practical 4 — method, variables, the marks examiners report students losing.

Verified against AQA 8462 (2026 spec)

Investigate the temperature change of reacting solutions — for example how the volume of one reactant affects the temperature change in neutralisation.

Apparatus

  • Polystyrene cup with a lid, standing in a beaker for insulation
  • Thermometer (0.5 C resolution) or temperature probe
  • Measuring cylinders
  • Reactants (e.g. dilute hydrochloric acid and sodium hydroxide)

Method

  1. 1Measure a fixed volume of the first solution (e.g. 25 cm3 of acid) into the insulated polystyrene cup.
  2. 2Record its starting temperature.
  3. 3Add a measured volume of the second reactant and put the lid on.
  4. 4Stir, and record the highest (exothermic) or lowest (endothermic) temperature reached.
  5. 5Calculate the temperature change.
  6. 6Repeat with different volumes of the second reactant (the independent variable).

Variables

Independent

Volume of the second reactant added

Dependent

Maximum (or minimum) temperature change

Control

  • Volume and concentration of the first reactant
  • Starting temperature
  • Insulation and stirring

Results & processing

  • Plot temperature change against the volume of reactant added.
  • For neutralisation the temperature change peaks when the acid and alkali exactly react — that peak identifies the reacting proportions.

Where students lose marks

Heat lost to the surroundings.

Fix: Use a lid and insulate the cup (polystyrene in a beaker) so the temperature change isn't underestimated.

Recording the temperature at a fixed time instead of at the peak.

Fix: Record the maximum (exothermic) or minimum (endothermic) temperature reached, not the reading after a set time.

Not stirring before reading.

Fix: Stir to spread the heat evenly so the thermometer reads the true temperature.

Improve the method

  • A lid and insulation reduce heat loss; take readings continuously to catch the true maximum or minimum.
  • Repeat and mean to reduce the effect of random error.

Try it — exam-style

Easy
2 marks
ORIGINAL

Give two ways a student could reduce heat loss to the surroundings in this experiment.

Medium
2 marks
ORIGINAL

Explain why a polystyrene cup gives a more accurate temperature change than a glass beaker.

Questions are written in the style of past AQA papers — never copied from them.

Drill it properly

AQA GCSE Chemistry flashcards

Exothermic vs endothermic and the energy-change ideas, drilled.

Chemistry resources

Every AQA chemistry tool and revision hub in one place.

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