Independent final check
Explain without the key
describe / state / explain
Final check
describe: give the features or what happens. state: give a concise answer. explain: give reasons and connect them to evidence.
A pupil blocks the outlet of a bicycle pump with her finger and pushes the handle in slowly. (a) Describe how the volume of the trapped air changes as she pushes harder. State the two conditions kept the same, so that only the pressure changed. (b) When she lets go, the handle moves back out to where it started. Explain, using kinetic particle theory, why the handle gets harder to push and why it moves back out.
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Scope and sources
Cambridge IGCSE Chemistry 0620 · 2026–2028 v2 · Original learning materials.
The effects of pressure and temperature on the volume of a gas (1.1.4) and their explanation with kinetic particle theory (Supplement 1.1.6), with a recap of gas particles from 1.1.2. The experiment uses one ideal sealed sample of air; gas-law equations and numerical gas calculations are not part of this module.
Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.
Official Cambridge syllabus