Igor writes:
An interesting experiment is to mix the ordinary ammonium nitrate (a fertilizer) with room temp. water. Try to put in as much ammonium nitrate as it is possible to dissolve.
You will see the temperature of the mixture DROP to below the freezing point (for pure water that is).
Wow. I did that 12 years ago and was amazed. A really easy way to get cold water if no freezer is available.
And for those who may think that endothermic reactions violate some basic law about entropy always increasing, I should point out that the increase in entropy from the uniform mixing of two different materials can more than compensate for the decrease in temperature. Ain't science wonderful? -- Eric Michael Cordian 0+ O:.T:.O:. Mathematical Munitions Division "Do What Thou Wilt Shall Be The Whole Of The Law"