What do cement and caramel have in common?
Strength of materials: The materials ability to resist an applied force.
Small camping gas stove (or any heating stove)
A small casserole to melt the sugar+water
A small rectangular kitchen pan or glass pyrex to pour the hot caramel.
Strawberry lace candy
4 small boxes or cans (matchboxes or empty tins).
A quite large screw or metal bolt 20-30 grams
We light the fire/heating source and pour water and sugar into the casserole.
When the mixture boils and becomes liquid caramel we pour it into the pan or glass container and let it thicken .
- The result is a large rectangular piece of caramel as its mold.
- We place it upon the 4 pillars and let the screw/bolt fall from half a meter high.
- The result is that the caramel shatters and the piece breaks like glass and have cutting edges.
- we give the shattered pieces of caramel to the students. While eating they observe and comment (discussion) .
Object of discussion:
Caramel consist of crystal that when unified/compressed by heat are very strong. But if a weight falls upon it then it is shattered/ as the screw did).
What do cement and caramel have in common? (discussion).
At first glance maybe nothing. But what about their molecular synthesis ( composition) ?
Cement is a non-responsive material that if studied under a microscope, we will see that it also consists of crystals. That means that it – more or less- has the same behavior under pressure, regression and bouncing as caramel. It is very strong when compressed but if punctured or something falls upon it shatters.
It is strong but cannot resist pressure and is shattered. So, if we construct a bridge by cement only with not metal beams in it, when under heavy pressure-while cars go over it- it will break/yield.
Let’s merge 2 materials
We create again a new caramel bar but this time, in the mold we stretch out from one side to the other strawberry lace candy, 1 cm apart ( as if they were metal beams or rods). Then we cover them with the melted caramel. When it is cool we place it again upon 4 pillars and throw the bolt from above.
This time our caramel bridge will bent under pressure but it will not break, it will crack but not shatter.
So that is why cement is so strong and engineers and construction companies put metal rods or a metal net to run through it in order for it not to break in any kind of pressure or force that falls upon it.