Science calculations
Maths questions often start with the command words 'calculate' or 'determine'. They will then have a blank space for you to show your working. It is important that you show your working; don't just write the answer down. You might earn marks for your working even if you get the answer incorrect.
In some maths questions you will be required to give the units. This may earn you an additional mark. Don't forget to check whether you need to do this.
Maths questions might include graphs and tables as well as calculations. Don't forget to take a ruler and calculator.
If drawing graphs, make sure you:
- put the independent variable on the x-axis and the dependant variable on the y-axis
- construct regular scales for the axes
- label the axes appropriately
- plot each point accurately
- decide whether the origin should be used as a data point
- draw a straight or curved line of best fit
If you are asked to calculate an answer and it has lots of decimal places, don't forget to use the same number of significant figures as the data in the question. For example, if two significant figures are used in the question, then usually your answer would also be to two significant figures. Don't forget to check your rounding.
Edexcel questions courtesy of Pearson Education Ltd.
Sample question 1 - Foundation
Question
The table shows the results of an investigation into the effect of distance on bubbles of gas given off during photosynthesis:
| Distance (in cm) | Bubbles counted in test 1 | Bubbles counted in test 2 | Bubbles counted in test 3 | Mean |
| 10 | 42 | 37 | 44 | 41 |
| 20 | 23 | 24 | 22 | |
| 30 | 10 | 11 | 12 | 11 |
| Distance (in cm) | 10 |
|---|---|
| Bubbles counted in test 1 | 42 |
| Bubbles counted in test 2 | 37 |
| Bubbles counted in test 3 | 44 |
| Mean | 41 |
| Distance (in cm) | 20 |
|---|---|
| Bubbles counted in test 1 | 23 |
| Bubbles counted in test 2 | 24 |
| Bubbles counted in test 3 | 22 |
| Mean |
| Distance (in cm) | 30 |
|---|---|
| Bubbles counted in test 1 | 10 |
| Bubbles counted in test 2 | 11 |
| Bubbles counted in test 3 | 12 |
| Mean | 11 |
Calculate the mean result for a distance of 20 cm. [2 mark]
- 23 + 24 + 22 Ă· 3 (1 mark)
- 69 Ă· 3 = 23 (1 mark)
Sample question 2 - Foundation
Question
A scientist measured the rate of water loss from a plant shoot using a potometer. The diagram shows the equipment used in the experiment.
The volume of water lost from the plant can be calculated by measuring the distance a bubble moves along the capillary tubing.
Calculate the rate of water loss from the plant in mm3/s if the volume of water lost was 12 mm3 in 10 minutes. [3 marks]
- 10 mins = 600 s (1 mark)
- 12 Ă· 600 (1 mark)
- 0.02 (mm3/s) (1 mark)
Sample question 3 - Higher
Question
A scientist investigated the effect of light intensity on the rate of photosynthesis of the aquatic Cabomba plant.
A lamp was used as a source of light. The lamp was placed at different distances (d) from the Cabomba plant, and the number of bubbles produced in 60 seconds was counted.
The number of bubbles produced in 60 seconds was used to calculate the rate of photosynthesis.
The light intensity was then calculated using the inverse square law \( \frac{1}{d^2}\).
The table shows the scientist's results.
| Distance (\(d\)) of lamp from Cabomba (cm) | Light intensity (arbitrary units) | Bubbles produced in 60 seconds |
| 5 | 0.0400 | 79 |
| 10 | 0.0100 | 21 |
| 15 | 0.0044 | 12 |
| 20 | 0.0025 | 7 |
| 25 | 5 | |
| 30 | 0.0011 | 4 |
| Distance (\(d\)) of lamp from Cabomba (cm) | 5 |
|---|---|
| Light intensity (arbitrary units) | 0.0400 |
| Bubbles produced in 60 seconds | 79 |
| Distance (\(d\)) of lamp from Cabomba (cm) | 10 |
|---|---|
| Light intensity (arbitrary units) | 0.0100 |
| Bubbles produced in 60 seconds | 21 |
| Distance (\(d\)) of lamp from Cabomba (cm) | 15 |
|---|---|
| Light intensity (arbitrary units) | 0.0044 |
| Bubbles produced in 60 seconds | 12 |
| Distance (\(d\)) of lamp from Cabomba (cm) | 20 |
|---|---|
| Light intensity (arbitrary units) | 0.0025 |
| Bubbles produced in 60 seconds | 7 |
| Distance (\(d\)) of lamp from Cabomba (cm) | 25 |
|---|---|
| Light intensity (arbitrary units) | |
| Bubbles produced in 60 seconds | 5 |
| Distance (\(d\)) of lamp from Cabomba (cm) | 30 |
|---|---|
| Light intensity (arbitrary units) | 0.0011 |
| Bubbles produced in 60 seconds | 4 |
Calculate the light intensity when the lamp is 25 cm from the Cabomba plant.
Light intensity = ............................... arbitrary units. [2 marks]
- 25 Ă— 25 = 625 (1 mark)
- 1 Ă· 625 = 0.0016 (1 mark)