A polymer, sodium alginate, reacts with calcium chloride to produce calcium alginate. Calcium alginate is a gel that is not soluble in water. A new branch of cooking, called molecular gastronomy, uses this technique to trap flavor sauces in gels to put over food. Not familiar with molecular gastronomy? Lifehacker has a good set of simple videos on the subject. You can order the kit that I used from Educational Innovations.
Entries in demo (81)
System A and System B monomers are mixed and polyurethane foam, a polymer, is produced. You can see the dramatic results in a clear cup, or a little more weird, in a latex glove.
This is a different version of the old egg suck into a milk bottle demo. I got this idea from a Steve Spangler demonstration in which he uses a water balloon instead of and egg. Basically a piece of burning paper is placed into a flask and then a water balloon sits on top. The oxygen gets used up during the reaction, creating a lower pressure inside the flask than outside. The balloon gets pushed in as a result.
Thanks to Joshua Buchman for correctly pointing out that I was completely wrong in my explanation. The video now has the correct explanation. The reason the balloon gets pushed into the flask is due to the rapid cooling of the hot gases in the flask once the chemical reaction stops. The gases condense as a result, lowering the pressure inside the flask and the atmospheric pressure pushes the balloon into the flask. I had wrongly assumed what had happened based on the recollections of demos that I had seen in the past.
I usually do this demo with a Gummy bear, but all I had was Gummy worms, so that's what I used. Sucrose has a lot of energy stored in the bonds that hold the carbon, hydrogen and oxygen atoms together. With a little bit of activation energy (melting the potassium chlorate) and a large supply of oxygen gas, (supplied by the potassium chlorate) that energy gets released in the form of light and heat energy (exothermic).
This is one of my favorite demos with students. Students get to hold methane bubbles in their hand and then experience the exothermic reaction when it reacts with oxygen in the air. The look on their faces is pure amazement.