Stress-Strain Graphs
Properties of Matter

Pick and mix

Practical Activity for 14-16 PRACTICAL PHYISCS

Class practical

Through this fun activity, students appreciate the importance of using scientific words precisely.

Apparatus and Materials

  • Sweets and biscuits, selection
  • Paper plates
  • Copies of blank stardiagrams (several per student)

Health & Safety and Technical Notes

This activity must be carried out in hygienic non-laboratory conditions, e.g. a screened-off area of canteen.

Cover the plates of samples with cling film if they are prepared in advance.

Read our standard health & safety guidance

The selection of sweets and biscuits should have a variety of mechanical properties and textures (e.g. toffee, boiled sweets, fudge, chocolate, pastilles, Mars bars, Snickers, Kit-Kat, wafers, crackers).

Break them up into bite size pieces.


  1. Eat the samples (one at a time!) and complete a star diagram for each one to record your assessment of its various properties. Plot points on the axes (e.g. a score of 7 for hardness means very hard) and join them to make a star.
  2. Working in a small group with a small number of samples, try to identify each sample from its star diagram.
  3. Discuss the terms used. In particular, be careful to distinguish between hard and brittle. Suggest examples of foodstuffs that are hard but not brittle (e.g. toffee), and brittle but not hard (e.g. a wafer).

Teaching Notes

  • This activity is intended as a fun introduction to more quantitative work on materials. You will probably want to follow it up with activities involving measurement of material properties.
  • Lead the discussion on to the importance of the precise use of words in physics (here, in the context of materials). In the food industry, specialist tasting panels are trained so that they agree on the precise meanings of the terms used. Many of these terms relate to properties that can be measured quantitatively.
  • It is worth pointing out to students that the food industry is a major employer of physicists. Physics is involved at all stages of product development, manufacturing, testing and packaging.
  • This experiment comes from...

    Salters Horners advanced Physics©

    ...University of York Science Education Group.

Diagrams are reproduced by permission of the copyright holders, Heinemann.

This experiment was safety-tested in December 2004

Stress-Strain Graphs
can be used to represent the quantity Stress Strain Young's Modulus
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