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Watch the cross disappear
Sodium thiosulfate solution reacts with dilute hydrochloric acid and forms solid sulfur. The mixture becomes cloudy. Place a flask on a black cross; time until the cross can no longer be seen from above.
Chemistry · Paper 2 · Foundation + Higher
Required practical: disappearing cross
No timer. Read the explanation after each answer.
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Daily 5 · Exam practice · Revision sheet ↓
Foundation + Higher. C6 · Rate and extent of chemical change.
AQA Combined Science Trilogy 8464 · 5.6.1.2 · Required practical 11. Original teaching notes, questions and diagrams. Animations are simplified models; speeds and practical readings are illustrative.