We worked on the chemistry badge tonight by doing 4 different science experiments. We divided the girls into 3 groups to round-robin the first 3 and then did the last experiment all together.
Oobleck gets its name from a substance in the Dr. Seuss book Bartholomew and the Oobleck. It is created by mixing corn starch and water to get a non-newtonion fluid — 1 part of water to 1.5–2 parts of corn starch. Most substances are either solid, liquid or gas. The fun thing about Oobleck is that it is a cross between a liquid and a solid. When you put pressure on it, it becomes rock-hard, but if you hold a ball of it in your hands, it will leak through your fingers. We spread a bunch out in a large pie plate and let girls experiment with putting different objects in it and watching them sink as though they were in quick-sand.
We didn’t get to see the results from this particular experiment straight away, but the girls got to learn about the scientific process by making 3 different types of crystals. Each group used one of salt, sugar or space crystal powder and got to hypothesize about which would fare best.
They started by dissolving their particular substance in boiling water in a Styrofoam cup. This took lots of stirring and teamwork! Then, they transferred it into a plastic cup so that crystals would be easier to see when they formed, set a popsicle stick accross the top of the cup, tied a string to it and dangled a paperclip inside.
We were able to look at the the next week and observed that the space crystal powder (from a science kit) worked best, followed by the salt (in the picture). The sugar hardly produced any at all. We will continue to watch as they grow through the weeks.
3. Yeast Balloons
Our third experiment was the most smelly. We used sugar, hot water and yeast to inflate a balloon. We started by putting 1 tsp of sugar in the bottom of a test tube, then 8g of yeast followed by some hot water (enough to fill the test tube most of the way up). Here came the tricky part. The girls had to mix it all up as quickly as possible before putting a balloon over the top. If they didn’t mix enough, not enough gas would form, but if they mixed too thoroughly or for too long, most of the gas would escape. We chose this experiment instead of one where you mix baking soda and vinegar because, although it is a similar process, is goes a little slower so you can see what happens more clearly. You can get more complete instructions here: http://www.sciencebob.com/experiments/yeast.php
For our last experiment, the whole group came back together and we talked about acids and bases. One of our other leaders had brought in a selection of liquids and powders and after telling them a little about the difference between bases and acids and the pH scale, the girls got to try to place them in order from most to least acid. Then, using an indicator made from red cabbage juice (http://science.howstuffworks.com/innovation/everyday-innovations/experiment1.htm), the girls got to see how close their guesses had been.