Subject: How could sodium acetate & water be used for both heating &cooling?

I'm a computer teacher at my school; where my students look at me like a joker; a teacher who knows enough to get around about almost any subject. They come to me to ask questions and one time I, even, demonstrated an endothermic reaction for them using Ammonium Nitrate and water. After one student pointed out some things I didn’t know about Ammonium Nitrate (toxicity and explosives potential), I set on finding a better salt and through lots of searching I eventually reached an answer to a question through your website; ID: 968444886.Ch. In the answer, the scientist mentions using Sodium Acetate amongst other things to dramatically bring down the temperature of water; basic formula for instant ice packs.

After looking up sodium acetate on wikipedia; http://en.wikipedia.org/wiki/Sodium_acetate, I discovered that its hazards and risks were dramatically less than those of Ammonium Nitrate. But what fascinated me was one of the uses mentioned for sodium acetate; heating pads. The site describes a somewhat detailed, yet still vague, for me, at least, description of how it works.

So, as mentioned in the question: How could sodium acetate & water be used for both heating & cooling?

Re: How could sodium acetate & water be used for both heating &cooling?