Can science really warm your hands

Science will never let your hands freeze!

Warn­ing! Only un­der adult su­per­vi­sion.


  • cal­ci­um chlo­ride;
  • wa­ter;
  • ther­mochromic stick­er;
  • mit­tens or gloves;
  • two re­seal­able plas­tic bags.

Step-by-step in­struc­tions

Pour some wa­ter into a re­seal­able plas­tic bag and seal it, then pour some cal­ci­um chlo­ride into an­oth­er. Put the bag with wa­ter into the sec­ond bag and seal it, then ap­ply a ther­mochromic stick­er. Put on some mit­tens or gloves and squeeze the bag of wa­ter un­til it opens, al­low­ing the wa­ter to leak out and mix with the cal­ci­um chlo­ride. The ther­mochromic stick­er changes col­ors!

Sci­en­tif­ic de­scrip­tion

When dis­solved in wa­ter, cal­ci­um chlo­ride breaks down into cal­ci­um and chlo­rine ions, which are im­me­di­ate­ly sur­round­ed by wa­ter mol­e­cules. They bond es­pe­cial­ly strong­ly to cal­ci­um ions. This process re­leas­es a lot of heat and the ther­mochromic stick­er changes col­ors! It’s quite com­fort­able to do this trick in mit­tens or gloves – it will quick­ly warm your frozen hands!

A sim­i­lar ex­per­i­ment is in­clud­ed in the “Ther­mal ef­fects” set from the MEL Sci­ence sub­scrip­tion.