AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Students should be able to plot, draw and interpret appropriate graphs.
Full specification wording
Osmosis: Students should be able to plot, draw and interpret appropriate graphs.
Osmosis data are often displayed as graphs.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 4 of 6
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Osmosis data are often displayed as graphs. When plotting, put the independent variable on the x-axis, such as concentration of sugar solution in mol/dm³, and the dependent variable on the y-axis, such as percentage change in mass. Choose a sensible scale, label both axes with quantity and unit, and plot points accurately. Draw either a line of best fit or a smooth curve as appropriate; do not join points with jagged straight segments unless the question asks for it. Interpreting the graph means describing the trend: as sugar concentration increases, percentage change in mass falls from positive to negative. The point where the line crosses the x-axis shows the concentration at which there is no change in mass, because water enters and leaves at equal rates.
What earns the marks
- Plots the independent variable on the x-axis and the dependent variable on the y-axis with correct labels and units.
- Chooses an even scale that uses the available grid and plots points accurately.
- Draws an appropriate line of best fit or smooth curve rather than joining every point with straight lines.
- Describes the trend, such as percentage change in mass decreasing as solute concentration increases.
- Identifies the intercept where the graph crosses the x-axis as the concentration with no net change in mass.
- Uses the graph to predict values, such as the percentage change in mass at a stated concentration.
Common mistakes and how to put them right
Swapping the axes so the dependent variable is on the x-axis.
Put it right by placing the variable you measured as a result on the y-axis.
Joining plotted points with separate straight lines when a line of best fit or smooth curve is expected.
Put it right by drawing a single trend line or curve.
Omitting units from axis labels.
Put it right by writing the quantity and its unit, such as percentage change in mass (%) or concentration (mol/dm³).
Exam tips
- Label each axis with both the quantity and its unit before plotting any points.
- Use a sharp pencil and small crosses for plotted points so the examiner can see exactly where each point lies.
- When describing a graph, quote data from it, such as the value at a stated concentration or the x-axis intercept.
Try the lesson
The start of the Osmosis: Students should be able to plot, draw and interpret appropriate graphs. lesson, made from checked teaching notes for this specification point.
Have a go first
Which type of graph is most suitable for showing how the mass of a potato strip changes over time?
Listen
Osmosis data are often displayed as graphs. When plotting, put the independent variable on the x-axis, such as concentration of sugar solution in mol/dm³, and the dependent variable on the y-axis, such as percentage change in mass. Choose a sensible scale, label both axes with quantity and unit, and plot points accurately. Draw either a line of best fit or a smooth curve as appropriate; do not join points with jagged straight segments unless the question asks for it. Interpreting the graph means describing the trend: as sugar concentration increases, percentage change in mass falls from positive to negative. The point where the line crosses the x-axis shows the concentration at which there is no change in mass, because water enters and leaves at equal rates. A strong answer earns marks for these points. Plots the independent variable on the x-axis and the dependent variable on the y-axis with correct labels and units. Chooses an even scale that uses the available grid and plots points accurately. Draws an appropriate line of best fit or smooth curve rather than joining every point with straight lines. Describes the trend, such as percentage change in mass decreasing as solute concentration increases. A common slip: Swapping the axes so the dependent variable is on the x-axis. Instead, placing the variable you measured as a result on the y-axis. Exam tip: Label each axis with both the quantity and its unit before plotting any points.
Key words
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Variables and axes
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Graph construction
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Trends and lines of best fit
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See every definition
- Variables and axes
- The independent variable goes on the x-axis, such as concentration of sugar solution in mol/dm³, and the dependent variable goes on the y-axis, such as percentage change in mass.
- Graph construction
- Choose a sensible scale, label both axes with quantity and unit, and plot points accurately.
- Trends and lines of best fit
- Draw either a line of best fit or a smooth curve as appropriate, rather than joining points with jagged straight segments unless the question asks for it.
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