This experiment looks at how something we think of as being brittle and weak can actually hold a heavy load under certain conditions. We’re going to investigate how strong an eggshell is.
How strong is an eggshell?
What you need:
- at least 4 eggs ( we broke a few making the domes )
- A pen
- Scissors or a sharp knife
- Heavy books
What to do:
- Tap the end of an egg gently on a hard surface to break it. Empty out the contents ( maybe use it to make scrambled egg? ) and rinse the inside of the shell. You will need 4 eggshells (you will probably need more than 4 eggs, but omlettes are lovely!). Take a moment to think how brittle eggs are.
- Draw a line around the egg as evenly as possible and using the line as a guide, carefully score the shell. Ask an adult to do this. It is worth spending a lot of time over this step, as we have found it’s frustratingly difficult. Ensure the scoring is continuous and completely encircles the egg.
- Very carefully break off pieces of shell up to the line. You can very carefully use the scissors to cut the shell. You need 4 half egg shells of the same height. The scoring helps to stop the cracks propogating past the score line (a branch of science in itself).
- Place the 4 shells in a rectangle shape, and slowly place books on top. See you many books you can add before the egg shells crack.
The Science Bit
Some shapes are stronger than others. Eggs which seem fragile are actually very strong in certain ways (try crushing an egg by squeezing the ends between your hands (maybe over a sink or outside!)).
Our egg shell forms a dome. A dome is very good at spreading weight evenly in all directions so that no part of the dome has to support more weight than another part. The downward force of the weight of the books is transferred evenly by the dome shape down to the work surface
Think more: What other shapes are strong? Where can you see these shapes in buildings or nature?
Starter: Have a look at bridges.
Take a look at our unbreakable egg experiment as well.