Cambridge Secondary (7-9). Stage 9. Science. Learner's Book - Unit 1: Photosynthesis and the carbon cycle - Question 53

Tubes A and B contain water plant; C and D contain small animals; E and F contain both. A, C and E are kept dark; B, D and F receive light. Each tube has hydrogencarbonate indicator and the same small platform.

Use the colours of the indicator to record how much carbon dioxide is present in each of the six tubes.