For our experiment this week, we did an oldie but a goodie...what happens when you combine baking soda and vinegar?
Perhaps because of some past experience building volcanoes, the kids guessed correctly that the combination would produce, in their words, "AN EXPLOSION!!!" (Aren't you glad this happens at my house and not yours?!) But more than that, they observed that the mixture of baking soda and vinegar interacts with a lit candle differently than would vinegar or baking soda alone. Passing a lit candle over baking soda had no effect on the flame. Same deal for the vinegar alone, but when you combine the two, and you get your EXPLOSION (i.e. bubbles), passing the candle over extinguishes the flame. Why does this happen? Mixing baking soda and vinegar is a chemical reaction, and as such, produces something new, carbon dioxide. Those are your bubbles, and they have the property of putting out a fire. That's why they put it an actual fire extinguishers. Cool, huh!?
Afterward the kids mixed cornstarch and water to create a really neato substance. What's so cool about "oobleck?" Well, it behaves like a liquid until you apply pressure to it. Then it behaves like a solid. Check out this video to see what I mean. http://www.instructables.com/id/SMEOL98FIWH3SZ4/