That’s not the science of making chocolate Brownies, but science with my Brownies. This happened now nearly three weeks ago, which shows how busy I’ve been. It worked really well, even with a few last minute changes. We had gone up to 26 Brownies the week before, cue me panicking because I really wanted them to work in smaller groups than their sixes, even more once two were now sevens… I needn’t have worried though as we only actually had 20 of them turn up.
We had 20 miniature forensic scientists, in teams of 5 named after famous scientists (Isaac Newton, Marie Curie, Albert Einstein, and Charles Darwin), and they rotated around three investigation. In order to discover which leader had stolen the kitchen keys (incidentally we still haven’t found them) they had create edible DNA for each leader, produce chromatograms, and test 6 substances with red cabbage indicator.
There was a leader attached to each investigation, and we had two lots of chromatograms going at once. The DNA and indicators took about 15 minutes each, and the chromatography about 7 or 8 minutes, so if you can have all groups doing the same activity at once I would. The Brownies did get really into it but with the difference in timings I could have done with having an extra activity that could have gone with the chromatography.
For anyone who’d like to try it out with their Brownies (or any other group for that matter, although I think probably Guides/Scouts are a bit old because they’ll have done it all at school by then) I’ve put links to the sheets I used for the Brownies. They include basic instructions and a record sheet.
The Science Bit!
Chromatography is a technique used to separate dyes (amongst other things). The ink in pens will be made up of a number of different coloured dyes, unless they are primary colours in which case it will be just one colour. Black and brown tend to give the best results as they are made up of the most colours. By placing water (a solvent) on top of a splodge (to use the technical term) of ink it dissolves the different dyes (the solutes). Some dyes will dissolve better in the water and so will travel further through the paper. I recommend using coffee filter paper, although you can get away with blotting paper if you’re desperate!
An indicator is a substance that will change colour depending on how acidic or alkali the substance being tested is. Red cabbage is surprisingly good at this. When you boil red cabbage in water it turns the water purple, if boiled in orange juice it would turn the orange juice bright pink… Rather than boiling everything with cabbage it is far easier just to boil it with water and add the cabbage water to whatever you want to test. I did it by chopping up the cabbage, and adding boiling water and cabbage to drinks bottles. Quick, easy and saves staining pans purple! There’s a list of colours on the document.
DNA, it’s what makes us, us. Everyone’s, bar identical twins, DNA is individual to themselves. So ideally do this last because it soon becomes blindingly obvious ‘whodunnit’ unless you have identical twins amongst your suspects! DNA contains four bases (adenine, guanine, cytosine and thymine), which pair up. Cytosine and guanine always pair up, and thymine and adenine pair up. You need to make up an example of the DNA found at the scene of the crime beforehand so they have something to compare it to. Unfortunately the key didn’t download properly…
We used gummy bears and cocktail sticks to make our DNA. Each base is allocated a colour of gummy bear. I made up a key of four sets of gummy bear colours per leader, which the Brownies then used to make them up in actual gummy bears. The key should have two columns of four, so the gummy bear colours match, like:
Then attach the pairs with cocktail sticks through their tummies, and then heads to feet with the ones above and below. To make it into a double helix, take the top horizontal stick and the bottom horizontal stick and twist!
The final link is for the Brownie record sheet. Get them to observe colour changes for the indicators, the others are just yes or no as to whether it matches the sample. You could get them to stick the chromatograms on.
If anyone does try this, let me know how you get on, and if you’ve any questions, ask away!