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:

  1. put the independent variable on the x-axis and the dependant variable on the y-axis
  2. construct regular scales for the axes
  3. label the axes appropriately
  4. plot each point accurately
  5. decide whether the origin should be used as a data point
  6. 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.

Sample question 1 - Foundation

Question

A student observed a cell with a microscope. The magnification of the eyepiece was x10. The magnification of the objective was x20.

a) What magnification was the student using? [1 mark]

The student measured a cell they were looking at as 0.5 mm.

b) Convert the cell measurement into micrometres. [1 mark]

This question has been written by a Bitesize consultant as a suggestion to the type of questions that may appear in an exam paper.

a) x200 [1]

The x10 magnification of the eyepiece lens should be multiplied by the x20 of the objective lens. 10 × 20 = x200.

b) 500 μm [1]

1 millimetre = 1000 μm, so 0.5mm × 1000 = 500 μm.

Sample question 2 - Foundation

Question

Students investigated the activity of the enzyme lipase in milk at different temperatures.

The results of the investigation are shown below:

Temperature (°C)Enzyme activity (a.u.)
1015
2032
3048
4054
5036

a) Plot the results on a grid where the x axis is 'Temperature in °C' and the y axis is 'Enzyme activity (a.u.)'. You must also:

  • choose a scale for the temperature axis [1 mark]
  • plot the results for enzyme activity shown in the table [2 marks]
  • join your plots with a ruler [1 mark]

b) From your graph:

i) Describe how the activity of the enzyme changes between the temperatures of 25°C and 45°C [1 mark]

ii) Calculate the change in enzyme activity between 15°C and 35°C. Show your working [2 marks]

Question courtesy of Eduqas.

a)

Graph showing enzyme activity between 10 degrees and 50 degrees celsius
  • suitable scale properly labelled [1]
  • correct plots [2] - it is possible to get one mark if there is one error but two errors will get no marks
  • clear line through the centre of the points with ruler [1]

b) i) Rises then falls/goes up and then goes down/goes to maximum and then drops. [1]

ii) Correct readings from graph should be shown in working:

= 51 - 23 [1]

= 28 [1]

The examiner will accept the answer 27.5 or 27 if the readings taken from the graph are slightly different.

Sample question 3 - Higher

Question

An experiment was set up to investigate the digestion of fat in milk by the enzyme lipase. A beaker containing milk and lipase was kept at a constant temperature in a water bath. The pH readout on the laptop was recorded every 5 minutes for 40 minutes. The results are shown below.

Time (minutes)pH
09.1
58.9
108.8
158.7
208.6
257.5
307.0
356.4
405.9

The average rate of fall in pH in the first 20 minutes is 0.025 pH units per minute. After 20 minutes bile was added to the beaker. Calculate the average rate of fall in pH units per minute in the 20 minutes after the bile was added. [1 mark]

______ pH units per minute.

Question courtesy of Eduqas.

0.135 [1] pH units per minute

  • at 20 minutes the pH was 8.6, then it fell to 5.9 at 40 minutes
  • therefore, the fall in pH in 20 minutes (from 20 - 40) was 8.6 - 5.9 = 2.7
  • to work out the rate of fall per minute would be 2.7 ÷ 20 = 0.135 pH units per minute