Wednesday, June 13, 2007

Science Camp: Day 2

I never got around to posting this last night, so it's a little late.

Yesterday, Day 2 of Science Camp, was another fun day. We started by finishing up the insect collecting. After about an hour of terrorizing butterflies, we moved to individual sessions.

In the chemistry session we did some DNA testing. For convenience I use a forensic DNA fingerprinting kit from BioRad. I've used this kit several times and it has always worked. I spread it over two days.

During the first day, I talk about DNA and how restriction enzymes can be used to make distinct DNA fragments. To illustrate this, I give them a strip of paper that has been subdivided into 40 boxes. I give them each a box of four crayons (like the ones you get a restaurants to entertain the wee ones until the food arrives). They are instructed to randomly color the boxes with the four different colors. Ideally, each color is used for 25% of the boxes. After they are done coloring, we get out our restriction enzymes: scissors. I pick a sequence of colors at random and anyone with that sequence cuts the "DNA" with the scissors. For example, I pick "red, blue, blue." Anyone with that sequence would cut after the second blue. Next we switch to a different enzyme that cuts after the sequence "Green, Yellow." Anyone with the sequence would cut after the yellow box. This continues for a few more rounds. Eventually, we compare everyones "DNA" fragments. I've never had anyone get the same # and size of fragments. It illustrates the point that everyones DNA is different and different fragments will be formed when the restriction enzymes are used.

After the coloring exercise, we went to the lab to add the EcoR1/Pst1 restriction enzyme mixture to DNA samples. There was a crime scene sample and 5 suspect samples. To do the transfers we use Eppendorf micropipets. A lot of time is spent teaching them house to use the pipets, but they love using the professional tools. They are closely supervised of course.

After the restriction enzyme has been added to the DNA it is incubated overnight. On Day 3 of Science Camp we will do electrophoresis.


The demo of the day involved the combustion of hydrogen balloons. This has been one of my favorite demos since I first saw it done at the University of Nebraska. The first balloon contains pure oxygen. A candle on the end of meter stick acts as a igniter. The pure oxygen balloon simply pops and the crowd is not amused.

What's the problem? There is no fuel, just oxygen.

The next balloon contains hydrogen. The candle on a stick is place under the balloon and boom! This amuses them a little more. Now that there is fuel, the "boom" is nice. However, the only source of oxygen is on the outside. The balloon must pop first, mix with the hydrogen and then combust.

The final balloon contains 2 parts hydrogen and 1 part oxygen. The candle is placed under the balloon and BOOM!!!! The blast is felt and heard by everyone near. Now we are talking chemistry.

It illustrates the importance of stoichiometry.

As an added bonus, I tried something I always wanted to try. I taped 5 hydrogen balloons together in a line. I put the candle under the first balloon and the chain reaction worked even better than expected. Oddly enough, the sequence of explosions had the rhythm just like the first part of "shave and a hair cut..." It was weird.

I didn't video tape it, but I am going to repeat that and tape it for sure.

5 comments:

Matt Jenks said...

I'm sure you want comments from the peanut gallery (though I'm more just like the nut gallery), but one of the cooler things we did in organic was to synthesize luminol and then use it to pick up traces of blood that was put in a dark room.

This was cool from two aspects: 1, the luminol glows when you pour the two components together to make it and 2, the luminol glows a different color when it's exposed to both blood and a blacklight. Since I've seen similar tests on CSI, I thought maybe kids would think this cool, too.

Chemgeek said...

oool. Maybe next year.

Chemgeek said...

I mean "Cool"

elderchemgeek said...

I'm glad you're closely supervising in the use of the professional tools...you don't want anyone shooting their eye out with an Eppendorf tip!

Someday I'll tell ya the story about my intern who shot herself in the stomach with a N2 powered needle.

Chemgeek said...

Needle to the stomach. Yikes.

That's as foolish as whacking ones foot with a hatchet.