The method that works every time, and the mistakes that lose the S mark.
Practice data: Values that need a little thought: 5s, 20s and 50s.
The scale method
Most lost graph marks are lost on the scale. Use this method for each axis, every time.
Find the range: from 0 (or from just below your smallest value) to your biggest value.
Divide by the number of big squares along that axis.
Round UP to an easy step: 1, 2 or 5, or the same × 10, 100, 0.1 … (so 1, 2, 5, 10, 20, 50, 100, 0.1, 0.2, 0.5 …). Never round down, or the data will not fit.
Check: does the data use more than half of the grid in this direction? If not, use the next easy step down, or start the axis just below your smallest value.
Write the scale on every big line, going up in the same step each time.
Never use the raw data as your scale
A scale is a ruler for the graph: every big square is worth the same amount. The data values are what you plot ON that ruler. If you write the data values (11, 47, 116 …) along the axis, the big squares are worth different amounts, the shape of the graph is wrong, and you lose the S mark and usually the P mark too.
Never use the raw data as your scale.
✗ Avoid The raw data written as the scale: 11, 47 and 116 are not evenly spaced values.✓ Good A linear scale: every big square is worth 20.
Other mistakes that lose the S mark
Spot the problem in each scale.
✗ Avoid Uneven: the steps change from 10 to 20 to 40. Every big square must be worth the same.✗ Avoid Awkward step of 3: hard to plot and read. Round up to 5 instead.✗ Avoid Too squashed for data that only reaches 116: it uses less than half the grid. Use 20 per big square.✓ Good Easy step, data up to 116 uses most of the axis.
Worked example: Worked example: 11, 47, 116 on 10 big squares
Range: 0 to 116.
116 ÷ 10 big squares = 11.6 per big square.
Round UP to an easy step: 11.6 → 20. (10 would be too small: 10 × 10 = 100, and 116 would not fit.)
The axis runs 0 to 200. The data reaches 116, which is 58% of the axis: more than half. ✓
One small square = 20 ÷ 5 = 4. So 47 is 2 big squares (40) plus 7 ÷ 4 ≈ 1¾ small squares.
The SLAPUK mark scheme
SLAPUK
Out of 5 (S L A P U). Out of 6 (S L A P U K) when there is more than one data set on the graph.
S
Scale
Even steps of 1, 2, 5 or 10 (×10ⁿ), and the data uses more than half the grid each way. Never use the raw data as your scale.
L
Line
Join the points with straight lines using a ruler, point to point. Best fit only when the question asks.
A
Axes
What you changed goes on x, what you measured goes on y. Copy the table headings as the labels.
P
Plots
Every point within half a small square, drawn as a small × or ⊙.
U
Units
Units after a slash or in brackets: "Time / min" or "Temperature (°C)".
K
Key
Only for two or more data sets: a key that says which line is which.
Practice graphs
1. Catalase and temperature
Catalase was tested at different temperatures and the oxygen collected in one minute was measured.
Plot a graph of volume of oxygen collected against temperature. Join the points with straight lines using a ruler.[5 marks]
Results Illustrative data
Temperature / °C
Volume of oxygen collected / cm³
10
4
20
9
30
17
40
26
50
14
60
3
1 · Axes, labels and scales
Put Temperature / °C (the independent variable) on the x-axis and Volume of oxygen collected / cm³ on the y-axis. This grid is 8 big squares across and 10 up; each big square has 5 × 5 small squares.
Set your scales, then tap the grid to plot each point.
Keyboard and screen-reader entry
Values are placed using the scale you set, so a wrong scale still gives a wrong graph – just like on paper.
Stuck on the scale?
Range ÷ big squares, then round UP to 1, 2 or 5 (× 10, 100 …). Check the data uses more than half the grid.
