Endothermic Reactions

Ammonium Chloride and Water

This reaction produces a rapid decrease in temperature. The easiest way to get the chemicals is from the instant cold packs (not the kind you stick in the freezer, the one time use ones). The package will contain a larger number of ammonium chloride pellets and a water bladder. Rather than use all the pellets at once, they can be stored and used in whatever quantity is needed for the transfer. Tap water works fine.

Exothermic Reactions

Oxidizing Iron

These one-use packets oxidize iron filings to produce heat..

Gas Producing Reactions

Vinegar and Baking Soda

The classic elementary science project volcano components. Mix vinegar and baking soda to generate carbon dioxide gas.

Alka Seltzer and Water

A spin on the baking soda reaction, but both components are actually in the seltzer and the water is just releasing them. Using vinegar may speed up the reaction, as will powdering the tablets.

Mentos and Coke

File:MentosCoke.jpg

Mixing mentos in diet coke = rapid gas expansion

Potentially much more dramatic than other gas producing reactions. Either use small quantities, contain it well, or both. If anything leaves the boundaries of the machine, you will be penalized.