Exothermic Reactions: Heat Packs & Sodium Acetate

[scottstown]

Hello,

There is something that has been puzzling me. Sorry if I don't use the correct terminology, this is not my field.

When a heat pack made of sodium acetate starts its exothermic reaction, does it release heat for only 15 seconds, but feels hot for ~30 minutes because the sodium acetate solution is acting as an insulator?

Or

When a sodium acetate exothermic reaction starts, does the chemical reaction happen for then entire length of the ~30mins.

If the sodium acetate solution is acting like an insulator, could another material be added to maintain the heat for longer?

Also, larger sized heat pads stay hot longer, is that due to size or reaction?

Thank you in advance for any help on the question,
Scott

 

[Amok]

I don't think that anyone actually knows this for sure. You'd have to know the rate of the reaction. I'm certain that it is a little bit of both.

As to adding an insulator to make the heat last longer, you could do that, but then it wouldn't be so hot, would it?

 

[Mapes]

I'd imagine the chemical reaction is active during almost the total time, because those thermal packs don't have much thermal mass. You can test this by taking an old pack, heating it up "manually" (e.g., in a plastic bag dipped in hot water, or in an oven), and seeing how long it takes to cool down. This time corresponds approximately to the time the pack would stay hot after the reactants are depleted.

 

[Amok]

http://www.wonderhowto.com/how-to-make-sodium-acetate-hot-ice-heating-pad-212411/



The reaction seems to occur very fast.

 

[LudusRex]

Hello Scott,

Thank you for your interest in exothermic reactions and heat packs. I would be happy to answer your questions and provide some clarification.

Firstly, an exothermic reaction is a chemical reaction that releases energy in the form of heat. In the case of heat packs, the reaction between sodium acetate and water is exothermic and releases heat. This heat is then used to warm up the pack and provide heat therapy.

To answer your first question, the heat released by the exothermic reaction of sodium acetate and water is not limited to just 15 seconds. The reaction continues for the entire duration of the pack's heating process, which is usually around 30 minutes. However, the heat may feel more intense in the first 15 seconds because that is when the reaction is at its most vigorous.

Regarding the feeling of heat lasting for around 30 minutes, this is due to the properties of sodium acetate solution. As the solution cools down, it solidifies and releases heat. This is known as a supercooling process, and it is what allows the heat pack to stay warm for an extended period.

It is possible to add other materials to the heat pack to maintain the heat for longer, but this would depend on the specific materials and their ability to conduct or retain heat.

The duration of heat provided by a heat pack is influenced by both its size and the reaction taking place. A larger heat pack will have more material to react and release heat, thus providing heat for a longer time. However, the reaction itself also plays a significant role in determining the duration of heat.

I hope this helps to answer your questions. If you have any further inquiries, please feel free to ask.
Best regards,