Hydrogencarbonate indicator changes colour when the concentration of carbon dioxide changes. It is purple when the carbon dioxide concentration is low, red when it is the same as in normal air and yellow when it is high.
A student sets up three sealed tubes of hydrogencarbonate indicator. All three tubes start red.
The Table shows the tubes and the colour of the indicator after 6 hours.
Table
| Tube | Contents | Conditions | Colour after 6 hours |
|---|---|---|---|
| A | leaf | bright light | purple |
| B | leaf | dark | yellow |
| C | no leaf | bright light | red |
Explain the result in tube A.
Explain the result in tube B.
Give the reason why the student set up tube C.
117 exam-style questions on OCR GCSE Biology 1.4 Photosynthesis, covering 1.4.1 Photosynthesisers as biomass producers, 1.4.2 Factors affecting the rate of photosynthesis, and 1.4.3 Limiting factors in photosynthesis. Each one has a worked solution and a mark scheme showing where the marks go.