Scrape the coloured coating off a number of same-coloured lollies (such as Smarties or jelly beans) and discard the rest of the lolly. Crush the coating using a mortar and pestle, adding water to make a coloured liquid. Put a drop of the liquid in the centre of a piece of filter paper. Add another drop of water onto the previous drop.
The colours should separate on the filter paper, making different rings according to the different food colourings used in the lollies.
SOAK the Smarties, as the colour is all on the outside. Cut a 1 cm strip from the edge in to the centre of a filter paper, spot the colour at the centre in a small spot, dry it with a hair dryer, and repeat several times. Then bend the 1 cm strip down, and sit the paper on a small beaker so the strip touches the solvent (water, ethanol etc) in the beaker. Red works best, from memory, though blacks are usually good as well, having several dyes.
Use Smarties or M & M's. Get the colour off by licking edge, and rubbing onto a (greylead) pencilled line ~ 2cm from end of chromatography strip, repeating the lick and rub to build up a dense colour. This way you get good results even from the pink and lilac smarties. I get the smallest boxes and each student gets one, they always dispose of the rest safely!!!
Red Cabbage pH indicator
Cut the leaves off a red cabbage. Grind them in a mortar and pestle with distilled water. Filter the liquid.
This should give an acid/base indicator. Will this also work with something like juice of red plums??
No need to grind: chop the cabbage roughly, and pour hot/boiling water over it, leave ten minutes. Reacts to dishwasher "detergent" (high in carb. soda, I think), and lots of other things.
Many flowers will do this, so will some felt pen dyes, and I once had a box of yellow face tissues go blue on me! Great chance for the kids to explore . . .
Black tea is another good choice as are rhubarb and beetroot. Use lemon juice or vinegar as the acid, carb. soda or dishwasher solid/liquid (usually perborate or other nasty, pH 10-11) for the base. Give a safety warning!
Use clean equipment for this experiment. Add 2M HCl (NOT recommended!!) (or vinegar) to sugar and heat it. This makes glucose (or toffee). Add baking soda and it makes honeycomb.
Dunno about that one Ummmm, 2M HCl OR vinegar???? This does NOT sound right!
There is something a bit odd about this. And toffee is not glucose, so far as I know, but I am ready to be amazed.
My antennae are quivering . . .
Method - best recipe in the PMU recipe book although most pre-70's cookbooks will have one. Use clean equipment for this experiment. Add vinegar( NOT HCl) to sugar and heat it until it turns golden brown (toffee). Cover the hand holding the saucepan with an oven mitt, then add baking soda and it froths right up and makes honeycomb if you pour it into a lightly greased pan.
Use clean equipment for this experiment. Combine baking soda, glucose and citric acid (perhaps tartaric acid too). Students can taste the results and come up with a mixture that they like best.
Carb Soda and citric acid (with castor sugar) for this one. Can colour with food dye and flavour with essences added to one component AND ALLOWED TO DRY BEFORE ADDING OTHERS.
Last year RACI (The chemical education society) put out a topic book on Kitchen Chemistry. It had a lot of really useful year 8 level stuff. The booklet was given to me by the Queensland branch. If you write to them you will probably be able to get the booklet. If you have troubles finding their address e-mail me and I will send you details of the booklet. Its just that I'm at home at the moment and the booklet is at work.
My experience with this topic has been with primary students (WA Year 6,7 aged 11-12). I can recommend a unit inspired by "There's an Emu in the Sky" Curriculum Corporation, Cliff Malcom ed called Cooking makes a difference. This is based on popcorn, eggs, flour and the changes to materials. Worked very well.
I have also found 'The Science Chef" (D'Amico and Eich Drummond, John Wiley, from Scitech) had some interesting one off experiments based on foods used in other cultures. WA Scitech has a cheap booklet called "Edible Science".
Last term I worked on Acids and Bases using the cabbage water indicator and then finished by experimenting with pH testers for pools/aquariums. Although the underlying science was too hard to touch with my crew, they had opportunities to conduct investigations both directed and self planned and they enjoyed testing household chemicals for acid/base/neutral. I seem to remember the book Chemistry in the Marketplace (Ben Sellinger) had some good material in it. How about felt-pen chromatography, or putting marshmallows in a vacuum chamber?
Some of the ASEP stuff (Acids and Bases) had some neat chemistry with foodstuffs. Somewhere there was some good stuff about testing dishwashing liquids with olive oil to get a comparison of their ability to saponify fats (and what's best value for your $) and all sorts of horrible things you can do with Draino or Dishwashing machine powder, which if nothing else will give your kids a reason to treat it with suspicion.
Of course, as kids my whole neigbourhood made cannons from corked bottles containing vinegar and sodium bicarbonate, but encouraging such activity might be dangerous.
I knew somebody who tried that, and he got a broken nose — a bit to either side, and he would have lost an eye. Definitely NOT a good idea — but of you warn kids, that tells them how to do it!
Just getting kids to handle food acids and mild bases is worthwhile in itself. Just make sure they follow safety precautions.
Three good titles from the shelves of the NSTC (Questacon) in Canberra: all published by Sterling from New York, each costing (OZ)$7.95 for 128 pp.
Here are the ones I bought:
Some of them will need watching -- Mandell's home-made compass won't work, because she did not stop to think about surface tension, flotation and the meniscus, and a few are old friends, but there is a good leavening of new ideas. To find out how to make the compass work, look at my versionof this toy.
- Simple Science Experiments with Everyday Materials, Muriel Mandell ISBN 0-8069-5764-6
- Simple Chemistry Experiments with Everyday Materials, Louis V Loeschnig, ISBN 0-8069-0689-8
- Simple Nature Experiments with Everyday Materials, D. Fredericks, ISBN 0-8069-1355-X