Science has never been something that I am good at. I barely made it through Biology and Physics in high school, and I chose Marine Biology and Marine Geology in college for a reason. (I actually managed to dissect a clam.)
My honey can't quite get his head around the fact that I managed to get out of higher education without any knowledge of chemistry. That's probably because he is pure scientist. He is also a little nuts. You see, lately it's been a little cold here in the upper Midwest, but he continues to ride his bicycle to work every day. Even when it was 25 below zero.
I bought him some hand warmers because I thought they might help him stay warm in cold weather. And he loved them, but was dismayed because they are designed to be used only once, good for ten hours of toastiness.
Then he realized that the warmth generated was from a simple chemical reaction. The hand warmers need oxygen to generate heat. If you deprive them of oxygen, say by putting them in a jar, as soon as the presence of a reactant is removed, the reaction will stop.
And if one jar is good, aren't two jars better? Yes, they seem to be, as the same pair of hand warmers has been warming his hands on his bike rides since last Thursday. Not every ride, as tonight's temperature of 20° doesn't require hand warmers.
My honey is tickled by the following answer to an FAQ on the product's website.
Are the warmers reusable/rechargable?
No. Our warmers are designed for one time use.
Sorry to contradict the company, but it's looking like they'll be good for intermittent one hour periods over more than a week.
Better living through chemistry!