Exothermic reaction question.

[So]

Homework - everyday example of an exothermic reaction. Begins with H and the 3rd letter may be N.

[Dr Slotter]

Doesn't fit with the 'n', but halogen light bulb?

[gmasterfunk]

Hand warmer?

[So]

gmasterfunk said:

Hand warmer?

We have a winner!

Thank you.

[Oldandslow]

Fire. You're crap at crosswords.