Day three was all about biopolymers. We extracted and precipitated DNA and messed with some starch based non-newtonian fluid.
First we put our DNA in a bottle. The campers swished about 10 mL of water in their mouths to extract cheek cells. These were added to some sodium lauryl sulfate solution to break up the cells. Then some EDTA was added to stop DNA-degrading enzymes. To precipitate the DNA, 95% ethanol was layered on the aqueous layer. This usually, but not always, created a few opaque strands of DNA. If they were careful, they could remove the DNA and put it in a vial.
This was fun, but it didn't work very well. Not every student was successful, but the ones that got DNA were pretty impressed.
Next, we made a royal mess playing with starch and water. This is a cheap and fun way to entertain a kid for minutes. Mixing starch and water in the right proportion creates a non-newtonian fluid. This fluid acts as a liquid when not under stress but behaves as a solid when under stress. A sharp finger poke will reveal its solid nature and a gentle finger poke will reveal its liquid nature.
The demo today was liquid nitrogen ice cream. I made a big batch;
1 quart heavy cream
1 quart half and half
2 cups sugar
a dash vanilla
Stir to dissolve the sugar.
Add liquid N2 slowly to freeze.