Graphical techniques

Nature of science:

The idea of correlation—can be tested in experiments whose results can be displayed graphically. (2.8)

• Graphical techniques are an effective means of communicating the effect of an independent variable on a dependent variable, and can lead to determination of physical quantities.
• Sketched graphs have labelled but unscaled axes, and are used to show qualitative trends, such as variables that are proportional or inversely proportional.
• Drawn graphs have labelled and scaled axes, and are used in quantitative measurements.

Applications and skills:

• Drawing graphs of experimental results including the correct choice of axes and scale.
• Interpretation of graphs in terms of the relationships of dependent and independent variables.
• Production and interpretation of best-fit lines or curves through data points, including an assessment of when it can and cannot be considered as a linear function.
• Calculation of quantities from graphs by measuring slope (gradient) and intercept, including appropriate units

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• Charts and graphs, which largely transcend language barriers, can facilitate communication between scientists worldwide.

Theory of knowledge:

• Graphs are a visual representation of data, and so use sense perception as a way of knowing. To what extent does their interpretation also rely on the other ways of knowing, such as language and reason?
  • Syllabus and cross-curricular links:
  • Topic 1.3—gas volume, temperature, pressure graphs
  • Topic 6.1—Maxwell–Boltzmann frequency distribution; concentration–time and rate– concentration graphs
  • Topic 16.2—Arrhenius plot to determine activation energy Topic 18.3—titration curves
  • Option B.7—enzyme kinetics
  • Option C.5—greenhouse effect; carbon dioxide concentration and global temperatures
  • Option C.7—first order/decay graph

Utilization:

• Graphical representations of data are widely used in diverse areas such as population, finance and climate modelling. Interpretation of these statistical trends can often lead to predictions, and so underpins the setting of government policies in many areas such as health and education.

Aims:

• Aim 7: Graph-plotting software may be used, including the use of spreadsheets and the derivation of best-fit lines and gradients.