Question 5
FAlgal balls are small beads of jelly that contain living algae.
Hydrogencarbonate indicator changes colour when the carbon dioxide concentration changes.
The Table shows the colour of the indicator at different carbon dioxide concentrations.
Table
| Carbon dioxide concentration | Colour of hydrogencarbonate indicator |
|---|---|
| higher than in air | yellow |
| the same as in air | red |
| lower than in air | purple |
A student set up five tubes, A to E, containing the same volume of red hydrogencarbonate indicator. Tubes A to D each contained 10 algal balls. Tube E contained no algal balls.
The Figure shows how the tubes were arranged from above.
Figure
After 1 hour, the student recorded the colour of the indicator in each tube.
The Table shows the results.
Table
| Tube | Colour of indicator after 1 hour |
|---|---|
| A | purple |
| B | red |
| C | yellow |
| D | yellow |
| E | red |
a.[2]
Explain the colour of the indicator in tube A.
b.[2]
Explain the colour of the indicator in tube D.
c.[2]
Explain why tube E was included in the investigation.
d.[2]
The indicator in tube C turned yellow even though tube C was in the light.
Suggest why.
e.[1]
The student judged the colour of the indicator by eye.
Suggest one way to make the results more accurate.
6.1 Photosynthesis Questions
44 exam-style questions on Edexcel GCSE Biology 6.1 Photosynthesis, covering 6.1.1 Photosynthetic organisms as producers, 6.1.2a Limiting factors on the rate of photosynthesis, 6.1.2b Interactions of limiting factors on photosynthesis, and 6.1.3 Inverse square law and light intensity. Each one has a worked solution and a mark scheme showing where the marks go.