soft boil egg and remove shell.
Take a bottle that bad an opening just a bit smaller than the egg. She the kids that the egg doesn't drop through.
Light some twisted paper and drop it into the bottle (bottle must not be platic!)
The difference in the pressure outside and insode the bottle will force the egg into the bottle without you touching it!
Has to ve a v soft boiled egg to work. Old style milk bottels are excellent for this, but they are hard to get now
Pop corn thing is good.
Mix un popped corn with butter or marg, get the kids to do this. tell them that the corn represents the atoms in a solid, and that the butter are the strong forces that give solids their properties....ie fixed shape....the mix doesn't flop about does it?
then put the mix into a pan and slowly start to heat it.....you are giving the solid energy and that allows the bonds to be broken. the corn can slip and slide over each other, this is why liquids can flow, and fill the sape of the container they are in,
add more heat and 'BANG' the atoms have enough evergy to fly appart, like the flying popcorn....this is why gases are so light.....the atoms are free to move.
(year 7 love this more than anything else I do with them....then we go outside and play at being atoms )