How to create cold?

Question

Are there any two chemicals (that I could expect to reasonably buy) that when mixed together, get cold? I know there are lots that get hot - I want the opposite.

Answer 1

dissolve ammonium nitrate (sometimes sold at garden stores, or online) in water. that simple. Like the above, it will freeze water around/on the container. I believe this is how the instant cold packs are made

Also, not combination, but solid co2 (dry ice) or liquid nitrogen are bot very, very cold and effective at cooling.

Answer 2

An easy way to get a cold solution is to mix ordinary crushed ice with salt (sodium chloride). Using a starting temperature of 0 degrees celsius for melting ice, add plenty of salt, then more ice, then salt. The sodium chloride solution has a much lower freezing point than pure water. This is not an endothermic reaction, but the drop in temperature is due to the latent heat of fusion of the solution. With a little practice, you can generate temperatures of minus 20 degrees in the solution.
This is a relatively harmless experiment, but temperatures of -20 can freeze flesh, so be wary. Do not touch the container with bare hands.

Answer 3

You'll need a highly endothermic reaction so how about this:

Solid barium hydroxide octahydrate (Ba(OH)2.8H2O) and ammonium thiocyanate (NH4SCN)

http://jchemed.chem.wisc.edu/jcesoft/cca/CCA3/MAIN/ENDO2/PAGE1.HTM

It's so cold, water around the beaker freezes!