Learning objective

Outline methods for conducting experiments to measure the rate of a reaction, including observing changes in mass or gas production.

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Exam focus

Cambridge IGCSE Combined ScienceChemical reactionsCore contentPractical objective

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Understand this objective

Quick explanation

This point belongs to Rate of reaction, especially Rate of reaction outcomes.
You need to be able to outline methods for conducting experiments to measure the rate of a reaction, including observing changes in mass or gas production.
The key ideas to know are Describe, Demonstrate, and Outline.
Use the linked flashcards and practice questions to check recall, then practise applying the idea in an exam-style answer.

Key concepts

DescribeDemonstrateOutline

Why it matters

This objective helps connect Rate of reaction outcomes to exam-style questions, flashcards, and revision notes for Rate of reaction.

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Paper 6Alternative to PracticalPractical1 marks

Method

In this experiment, you will mix hydrochloric acid with sodium thiosulfate and observe the time taken for a cross to disappear.

Step	Description
1	Measure 50 ml of sodium thiosulfate solution.
2	Add 10 ml of hydrochloric acid to the sodium thiosulfate.
3	Start a timer as soon as the acid is added.
4	Observe the cross under the solution and stop the timer when it is no longer visible.

a
State the independent variable in this experiment.
Your answer
Aim for approximately 1 distinct marking point.
[1]

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