Learning about science and the experimental method is a lot of fun. Mix this with that and see what you get! Sometimes the result can be, well, hazardous to your health. But if you survive such an encounter, you have to tell all your friends. With the internet, you can tell everyone, and even show the video. But seeing it done doesn't make these experiments any safer. Remember, the ones who survived to tell their tales are the lucky ones. Most of the experiments detailed here were done by professionals.
Theodore Grey has an index of Fun/Dangerous Experiments. He includes a special note for teenagers about mortality and how it will mean something in a few years. And about safety glasses.
Why are glasses so important? Because having your cheeks ripped off by shrapnel, your hair burned to the roots, and your nose split open and folded up over your forehead is nothing, nothing compared to being blind for the rest of your life. Not even close.
He then documents quite a few experiments with the elements, including this fascinating account of his Sodium Party. Besides the explosive combination of sodium and water, I found out there are butterflies who collect sodium, and how to protect fish from exploding sodium.
More dangerous experiments after the jump.
Thermite is a combination of materials that will produce a large amount of heat. The process is used to weld railroad ties. From Wikipedia:
Although the reactants are stable at room temperature, they burn with an extremely intense exothermic reaction when they are heated to ignition temperature. The products emerge as liquids due to the high temperatures reached (up to 2500 °C (4500 °F) with iron(III) oxide)—although the actual temperature reached depends on how quickly heat can escape to the surrounding environment. Thermite contains its own supply of oxygen and does not require any external source of air. Consequently, it cannot be smothered and may ignite in any environment, given sufficient initial heat. It will burn well while wet and cannot be extinguished with water.
Of course, with a reaction like that, people are going to use it for entertainment. Thermite is not difficult to make. The danger of igniting the stuff should be apparant in this video.
Other dangerous links:
Dangerous Laboratories
Mad Coiler's High Voltage Page
Fun Things to Do with Microwave Ovens
The Dangerous Experiments Flickr pool.