Wednesday, January 12, 2011 at 8:01AM 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.
Saturday, January 1, 2011 at 4:47PM 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.
Darren Fix
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.
Thursday, December 16, 2010 at 7:32AM 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).
Wednesday, December 8, 2010 at 8:19AM 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.
Sunday, December 5, 2010 at 5:54PM Energy is needed to start a chemical reaction. Unsurprisingly this is called activation energy. The video above shows the activation needed to make red phosphorus react with oxygen in the air.
Darren Fix
A former brilliant student of mine, Hayden Parker, informed me that the head of safety matches are not made of red phosphorus. Science Theatre at Michigan State University explains.
A "striking surface" is made of sand, powdered glass, and a chemical called "red phosphorus". The head of a safety match is made of sulfur, glass powder, and an oxidizing agent.
This is why safety matches cannot be lit on any surface. The striking surface contains the red phosphorus and not the match itself.
