Last night was the Salmon Bay Science Fair. Lochlan decided he wanted to participate, and after talking it over with Amy, chose 3 "kitchen chemistry" experiments/demonstrations. Amy did a fantastic job pulling together all of the materials and documentation, and Lochlan was a great helper.
The first demonstration was a comparison of a solid (carrot), a liquid (water) and Oobleck, a mixture of corn starch and water that is a non-Newtonian fluid. In other words, Oobleck behaves like a liquid when poured (it fills the container in which it's placed) but behaves like a solid when a force acts upon it, such as hitting it or trying to quickly jab your finger into it. That was a big hit with all the kids.
The second demonstration was inflating a balloon by filling it with baking soda, then placing it over a pop bottle filled with vinegar. This is a two-step or "double replacement" reaction, in which acetic acid (vinegar) reacts with sodium bicarbonate (baking soda) to produce a form of carbonic acid, which is unstable and breaks down into water and carbon dioxide. The CO2 inflates the balloon.
The third demonstration was really cool. It turns out red cabbages have a chemical in them that can serve as a pH indicator. The molecule is called flavin, which is an anthocyanin. Amy pureed some red cabbage and created a solution with water, and gathered a whole bunch of commonly found kitchen ingredients (onion powder, vinegar, cream of tartar, milk, etc). She brought a bunch of baby food jars and some water. The kids could choose which kitchen ingredient to place in the baby food jars, create a solution with water, then use an eye dropper to place the cabbage solution into the jar. Very acidic solutions turn the anthcyanin red or pink, neutral solutions will turn it purplish, and basic solutions will turn it blue or bluish green. This was a HUGE hit with all the kids, and one 1st grader named Elizabeth came by three times with her father to test different compounds. She said it was her favorite exhibit of the whole fair!
It was really wonderful to watch Lochlan explaining all of this and assisting the other students with the demonstrations. He had a great time and I think he'll want to do it again next year. :)
