How does hand warmer work

More pores mean more air, so the pouch for toe warmers has more holes than the one for hands since, you know, tight stinky snow boots have less circulation. This porous material holds the water necessary for the oxidizing reaction to occur.

It's also thermally conductive, so it helps spread heat evenly. To make it, heat charcoal in the presence of an oxidizer. It expands to create millions of tiny pores between its carbon atoms, increasing the surface area to as much as 2, square meters per gram. A pound of activated charcoal has the same surface area as six football fields—that's a lot of crannies for storing water. Like in your kitchen, salt amplifies things. As a de-icer in snowy cities, salt can cause car underbellies to corrode.

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Sign in with a different account. Need Help? Membership Categories. Regular or Affiliate Member. Graduate Student Member. Undergraduate Student Member. Benefits Enjoy these benefits no matter which membership you pick. Thank you! Small packets of warmth work through a simple exothermic reaction by Linda Wang January 25, A version of this story appeared in Volume 88, Issue 4. Why glass recycling in the US is broken Scientists synthesize large borophene crystals Glowing dyes could store digital data for the long term.

For winter sports enthusiasts, hand warmers can mean the difference between calling it a day early and playing outside for as long as possible. You might also like The Science Of Feeding Soldiers. Materials For Adventure. What's that stuff? Pool Chemicals. Share X. To send an e-mail to multiple recipients, separate e-mail addresses with a comma, semicolon, or both. Submit Sending I have a pair of re usable hand warmers but i don't know how long to re warm them for, does anyone know?

They are very painful when brushed against anything. I have used a magnifying glass to see the slivers but can't see anything.. I missed your point, now obvious, the packaging process. At a guess they are mixed and packaged in an oxygen free environment. Permeable… a common mistake to use the term Porous. Porosity is a volumetric term, Permeability is a flow term…ie air flowing through permeable membrane.

Much of your body operates on semi-permeable membrane processes. Thanks for that! Could you explain what volumetric means in regard to porosity? I want to understand more fully and explain to my kids. Am I correct in understanding porous means the materials have space or room within it, volume wise, to take in more liquid or solid material?

And porous means the outer surface can allow gas to flow, but not necessarily absorb as a porous material can? Porosity or void fraction is a measure of the void i. Your email address will not be published. Notify me of followup comments via email. You can also subscribe without commenting. Not today. You need something to read? We have something to read! Steve on December 14, at am. Mo on December 14, at pm. I always wondered. Tami Kidd-Brown on November 11, at pm.

Gary on December 14, at pm. Gloria Parsons on February 20, at pm. Rho on March 2, at pm. Ken on April 20, at am. How do they package them without activating Reply.