Australia's Science Forum

Can anyone help with this demo. Its the one where sultanas rise and fall due to attached air bubbles. I have looked on the internet, and tried using Alka-Seltzer, also baking powder and vinegar. One lone sultana out of 6 was obliging, the rest refused to budge. I also tried muscats and currants. No better.

Are there any variations on this theme that would be good for a demo?

We have a very old one "dancing mothballs" which uses baking soda and vinegar. Not sure if its suitable any more, may be alright as a demo? (Naphthalene ok for years 11 and 12)

Regards Trudy

Hi Barbara
my head of science said to use soda water or any fizzy drink with bubbles
Rhonda

We do that one every year as an observation exercise in a Year 7 Prac test. Some years it works brilliantly, (like this year!) some years it is a flop (like last year!)

The instructions we give the kids are as follows

1. Fill a beaker with water to the 150mL mark
2. Stir in one heaped teaspoon of Bi-Carb Soda until dissolved
3. Add three sultanas to the beaker. Make sure they are sitting on the bottom. (Poke if necessary!)
4. Measure 20 Mls of vinegar in a measuring cylindar and add to beaker
5. Draw a labled diagram to illistrate what happens
6. Describe what happens in the beaker.

You probably do not need point 5 and 6.

This year, those little 'tanas just kept bobbing up and down for hours after we finished the test! Last year? Not so!

regards
Ian

Thanks guys.... it must be one of those "years" for me then. Yesterday, they all sat on the bottom. I came in this morning and they are all plumped up and staying at the top. Are they useless once theyve swelled up?

Do you like Boiled Fruit cake? Maybe you could make a cake for Richards dog.

Ian

Ian What a card!
I'm at the stage where I am getting frustrated with sultanas!, and that sounds ODD to me

OK supporters.....
I set up another with fizzy lemonade. One little sultana is knocking himself out (other 2 refusing to budge). So I will go with that little fella. Hope it still doing it when the class comes in !?

Just some feedback.... we ditched the sultanas in the end.
We had great results with a small tank filled with lemonade, and a handful of dried corn kernels!
Thanks for all those ideas!