In a sodium thiosulfate experiment, the time for a cross to disappear decreases from 80 s to 40 s. Using 1/t 1/t\,1/t as a rate measure, how does the rate change?
It halves
It stays the same
It doubles
It becomes four times smaller
127 exam-style questions on Edexcel GCSE Chemistry 8.1 Rates of reaction, covering 8.1.1 Measuring and interpreting rates of reaction, 8.1.2 Collision theory and the factors affecting rate, and 8.1.3 Catalysts and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.