A Bouncing Egg

It's easy to make a rubber egg and the chemistry of removing the the eggshell with vinegar is interesting.
What you're left with is a totally embarrassed naked egg and a cool piece of science!
Here goes.....

What you need.....

egg.jpgvinegar.jpgjar.jpg
P1200011.JPG
Place your egg in the jar. Cover it with white vinegar.
P1200014.JPG
Screw on the lid. Leave your egg alone for 4 days.
P1200116.JPG
What are all those bubbles...?
P1200211-1.JPG
The naked egg - rubbery, swollen and ready to bounce!

What's happening...

The egg shell is made of calcium carbonate - so are your
bones. Calcium makes them strong.
The white vinegar is an acid. It dissolves the calcium in
the egg shell. What's left? Carbon dioxide! So those
tiny bubbles are full of carbon dioxide gas.

Underneath the shell is a tough, rubbery membrane.
This isn't dissolved by the vinegar - that's why the egg yolk
and white don't spill out when the shell dissolves.
The membrane isn't quite waterproof so some of the
vinegar seeps through it, into the egg. That's why the egg
gets bigger.
P1200245-1.JPG
You will know when the egg is ready - there is no more shell
to dissolve, so there are no more carbon dioxide bubbles.
Empty the vinegar and replace it with water. Your egg is
ready to bounce...
P1200249-1.JPG
Our expectations were high!
We made a 5cm graduated scale up a science stand.
At 5cm the eggs bounced safely. At 10cm they went....

splat.jpg

A Folding Egg....

This time, blow the egg and put the empty shell in the vinegar.
Leave it for about 10 days.......

The shell dissolves and leaves the membrane.
Gently squeeze the fluid out of the membrane.
You can blow it up by gently blowing air into it through the
blow-holes you made at the start.It looks like a real egg!
Gently squeeze it again. Drop the egg in a tall, clear glass.
Cover the top of the glass with your hand and shake the glass.
Air will slowly work it's way into the egg and Abracadabra...
the egg will magically restore itself.

Hint: Dust the egg membrane with some talcum powder.
Try to get some of the powder inside the egg as well.
The powder will help keep the egg membrane from drying out
and cracking - and it makes the egg look even more real.
This magic trick is over 100 years old!
folding_egg.jpg
The egg membrane ready for folding....