Exothermic Reaction

Mg + 2H₂O → Mg(OH)₂ + H₂

Don't eat the Mg

Don't expose the H₂ to flame

Don't eat the yellow snow (per Frank Zappa)

Or how about:

NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l) ?

160 F is reachable with a mixture of concentrated sulfuric acid slowly added to water with stirring and goggles. You can boil the water, so be careful, this can be risky.

Sadly, any exothermic reaction to make 160 can also make 260 and throw boiling acid in your face.

What happens there is the hydration of concentrated sulfuric acid into the hydrated form.

You can also use an acid and a base, which combine to make a salt solution adn water, as in NaOH + HCl into Na+ and Cl- and H2O. In effect you burn hydrogen and get that heat and lose the heat cost of dissociation of the acids.

Anything like this can also be dangerous.

a bit more here

http://en.wikipedia.org/wiki/Exothermic

Mix some lye (Drano) in water. Toss in a piece of aluminum. Do this in a well-ventilated space, not your garage and forget it, like I did...

Take a look at the handwarmer packets sold in sporting good stores. They contain iron filings and an oxidizer and can get really hot. Edmund

As above, the hand warmer pack I have says it gets to 70°C (158°F).

It would seem that no one understood your "relatively safe chemicals". There are many ways to achieve the temperture you require, but we first need to know: Are you trying to achieve this temperature in air, as in an oven or a room? Or in a solution? What kind of quantity is involved? Could you use a propane or natural gas flame, for example?

I would like something the size of a hand warmer. It needs to be self contained much like the hand warmers work. The reactions that give off gasses is not acceptable.