1. Chilled Confectionary

2. Its ability to withstand an applied stress without failure.
Strength
Toughness
Brittle
Resistivity
Ductile
A measure of how strongly a material opposes the flow of electric current
the extent in which solid materials can be plastically deformed without fracture.
Its ability to withstand an applied stress without failure.
The amount of energy per volume that a material can absorb before rupturing.
When subjected to stress, it fails without significant deformation. Failure is often accompanied by a snapping sound.
Which terms would chocolate bars have significant values in?

3. Its ability to withstand an applied stress without failure.
When subjected to stress, it fails without significant deformation. Failure is often accompanied by a snapping sound.
Brittle
A measure of how strongly a material opposes the flow of electric current
Resistivity
the extent in which solid materials can be plastically deformed without fracture.
Ductile
Strength
Its ability to withstand an applied stress without failure.
The amount of energy per volume that a material can absorb before rupturing.
Toughness

4. Introduction
Mechanical properties of materials depend on their microstructures.
‘Structure determines function’
Another important factor in determining the behaviour is the temperature.
Here you are asked to consider a material, predict its response to temperature, make an observation and explain the effect.

5. Comparing warm and cold bars
1. Chill one of the bars long enough for you to be sure that it has reached the freezer temperature. You may wish to place a thermometer near the bar to establish its final temperature. Remember that freezer temperatures can be around – 20 °C; make sure that the thermometer goes low enough.
2. Whilst the bar is cooling predict how you expect the mechanical properties to vary with temperature, relating this to the particles of which the bar is made up.
Also devise a way to test the mechanical properties of the bars. Eating them and using your teeth as the arbiter is not an option given the low temperature of the chilled bar. The test should be quick, probably destructive, and should if possible yield quantitative estimates of the differences.
6. Make your observations and try to explain the results. Use the terms you learnt in the earlier part of the course as far as possible: e.g. is the bar tough, brittle, strong, etc?
7. Speculate on why it is recommended that you do not use a Crunchie bar.

6. Predict how you expect the mechanical properties to vary with temperature, relating this to the particles of which the bar is made up.
I think that…

7. My method to determine the mechanical properties of a chocolate bar is:

8. Observations and explanations
Observations and explanations. Use some of the terms from the start of the lesson
I found that…

9. Why is it not recommended to use a Crunchie bar?
It is not recommended because…

10. Three-point bending 10 g 10 g 10 g 10 g Slotted masses Chocolate bar
Pencils

11. 10 g
10 g
10 g
10 g