02.23.2018
Experiment Leaders: Annie and Bree
For this set of experiments, we were able to show the students some different examples of membranes and demo diffusion and selective permeability.
We started with an introduction of diffusion and osmosis using skittles. The students were told to arrange skittles on the bottom of a bowl in any pattern they’d like. Then, they added water to the bowl until the water covered the bottom of the bowl and touched all the skittles. The students then observed the colors of the skittles diffusing into the water. This experiment was a great little hands-on demo that produced very pretty results in the form of rainbows!!!
After the skittles experiment, we moved on to our “Naked Egg” Demo. A “Naked Egg” is simply an egg whose white shell has been dissolved off with white vinegar. The clear membrane is still intact and holding the yolk inside! We told the students how to make these and passed around a premade “Naked Egg” for them to poke. Then, we asked the students to form hypotheses on what would happen if we soaked these eggs overnight in water and corn syrup. After they made several guesses, we passed around “Naked Eggs” that we had soaked the night before. Once they saw that the water eggs had gotten bigger and the corn syrup eggs got smaller, we asked them why this happened. They were able to figure out that water had diffused into the water-soaked egg and out of the corn syrup-soaked egg! The students really enjoyed being able to touch the “Naked Eggs.”
The last experiment demoed selective permeability. We gave each student a balloon and had them put a few drops of vanilla extract inside. They blew up their balloons and tied them shut. We then had them smell the outside of the balloon, which smelled of vanilla! We discussed with each group why the vanilla molecules were able to escape, but the air could not. This is when we introduced the term selective permeability. After seperate group discussions, we brought the class back together and asked for some examples of membranes that are selectively permeable. The students were so great at coming up with examples! We got the examples relevant to what they’ve been learning in class, cell membranes. We got some examples that we see in everyday life, such as a pasta strainer. But our favorite example was when a student said, “Bree’s shirt is selectively permeable because sweat and water can go in and out, but not her!”
We had a blast doing experiments at Venture Academy and we are so excited to go back next month!
