AQA GCSE Chemistry – Rates of Reaction – Sodium Thiosulfate (Disappearing Cross)

Help GCSE Chemistry students develop confidence in answering extended-response questions on the AQA Rates of Reaction required practical.

This scaffolded exam-practice resource focuses on investigating how concentration affects the rate of reaction between sodium thiosulfate and hydrochloric acid, using the disappearing cross method.

What's included:

• A 6-mark exam-style question based on the sodium thiosulfate disappearing cross investigation
• Success criteria, command word guidance and key scientific vocabulary
• A scaffolded fill-in-the-gaps activity with a word bank
• A model answer to support independent learning and self-assessment
• A printable PDF and an editable PowerPoint version

Skills covered:

• Describing a valid practical method using sodium thiosulfate and hydrochloric acid
• Investigating how concentration affects reaction rate
• Identifying independent, dependent and control variables
• Measuring the time taken for a cross to disappear as the solution becomes cloudy
• Improving reliability through repeated measurements
• Recording and evaluating experimental results

Suitable for: AQA GCSE Chemistry and Combined Science students, classroom activities, revision lessons, homework and exam preparation.