Cambridge Secondary (7-9). Stage 9. Science. Learner's Book - Unit 8: Rates of reaction - Question 61

Investigate sodium thiosulfate solution with dilute hydrochloric acid at different temperatures, using 10 cm³ thiosulfate solution and 1 cm³ acid each trial, timing when sulfur precipitate hides a black cross. What did you find out that will help your final investigation?