Exciting science you can do at home!

[Blandmum]

For everyone thinking of things to do on a dull Sunday

spectacualar egg in a bottle experiment This works well with a milk bottle BTW

Bouncing custard balls

3: Bouncing Custard Balls
Using a simple cross-linking reaction between two polymers, a bouncy ball can be
made.
What you will need
15 cm3 PVA glue
measuring cylinder
borax (sodium tetraborate Na2B4O7.10H20)
custard powder
test tube
test tube rack
100 cm3 beaker
glass stirring rod
spatula
eye protection
What you do
1 Make up a borax solution by adding a spatula of borax to a test tube
containing 10 cm3 water.
2 Pour 15 cm3 PVA glue into the beaker.
3 Add 2 spatulas of custard powder and 1 spatula dry borax.
4 Add 0.5 cm3 of the borax solution and stir vigorously. Keep stirring until the
mixture is smooth.
5 Remove the mixture from the beaker, shape it into a ball and work it between
your hands for about 2 minutes. You should feel the ball gradually becoming
more elastic.
6 Test the ball to see how well it bounces.
Wash your hands afterwards.
Troubleshooting:
If the ball is brittle, you have
used too much borax.
If the ball is too soft and not elastic,
you have not used enough borax.
Note:
Your custard balls will dry out and lose
their bounce unless you keep
them in a plastic bag.
Eye protection must be worn.

Note to parents.....very messy!

[philippat]

the simple one dd loves:

very dark 2p coin
sprinkle salt over it
shake vinegar on it
shiny coin!

the salt and vinegar combine to form an acid which cleans the patina off the coin (help with the science bit appreciated, please )

puts you off putting salt & vinegar on your chips, too...

[Blandmum]

It could be that the sodiun chloride in the salt reacts with the acetic acid in the vinegar to form sodium acetate and hydrochloric acid (not sure if this would happen btw)

Hydrochloric acid is a 'stonger' acid than acetic. It reacts with the metal oxide (the tarnish) to form a soluable salt and water = Shiny coins

[yoyo]

Will try that out this week martianbishop.

[roisin]

Can you buy borax from the chemist?

Ooh I want to do the egg/bottle one now! Can I steal a milkbottle from someone's doorstep?

[jabberwocky]

You should be able to find borax in the laundry section at the grocery/department store.

[puff]

Brill ideas - anymore I can add to my box of tricks so ds1 thinks I am supermum !

[Blandmum]

The egg one is eggcellent [groan]

Make sure at the end that the kids realise that it isn't the vacuum that 'sucks' the egg in but the pressure of the air outside that forces the egg downwards. The ballencing pressure of the gas in the bottle having been removed IYSWIM.

It is fab.

A good one for those of you using disposable nappies. Take out some of the crystals.....do this by shreading the nappy in a zip loc bag....the crystals can be an irritant so don't get them on your hands, eyes or breath them in.

Gice the kids a tiny amount (weigh it if you have good scales that weigh in grams) and some blue coloured water. Put the crustals in a large bown and challence them to see haw much water they will absorb....vast amounts!) The kids need to add the water little by little. They can weigh it at the end and if you like calculate the amount of water absorbed and the 100% of crystal mass that can be absorbed.

Trust me this is quite amazing!

Cookie chip challenge.

tell the kids that choc chip cookies represent gold nuggets in rock. Their job is to sparate the chips from the cookie and get the most out. They can chip them out, disolve them out, try filtering, evaporating water use etc. they then calculate the efficiency of each method.