Wednesday, June 11, 2008

Science Camp 2008: Day 3

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.



Russ said...

Have you ever seen the Youtube video where they filled a pool with non-newtonian fluid? They can run across the surface, but if they stop, they sink.

the indefatigable mjenks said...

They did the same thing on Mythbusters while trying to do some ninja myths. Not only was there non-Newtonian liquids, but there were also ninjas: win-win situation.

Chemgeek said...

I have seen the YouTube one but not the Mythbusters one.

However, in each of the three sections, several campers told me about it. One thing these kids love is Mythbusters.

the indefatigable mjenks said...

Everybody loves crazy guys blowin' stuff up.