rising and sinking sultanas

[Ocean Breeze]

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?

[Trudy]

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

[rp]

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

[Ian]

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

[Ocean Breeze]

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?

[Ian]

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

Ian

[Ocean Breeze]

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

[Ocean Breeze]

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 !?

[Ocean Breeze]

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!