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Anne Marie Helmenstine, Ph.D.

Make Hot Ice - Heating Pad Chemistry

By July 22, 2013

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Here's an easy chemistry project you can do in which you take a clear liquid and instantaneously solidify it into hot 'ice'. It isn't water ice, however. This is how you make crystals of sodium acetate, which is used in hand warmers and chemical heating pads and hot packs.

Hot Ice Materials

  • sodium acetate
  • water
  • saucepan
  • glass or pan

Making Your Own Sodium Acetate Monohydrate

If you don't have any sodium acetate monohydrate you can make your own. Add baking soda (sodium bicarbonate) to vinegar (weak acetic acid) until the mixture stops fizzing. This will give you an aqueous solution of sodium acetate. If you boil off the water, you'll be left with the sodium acetate. Expect to use a lot of baking soda and vinegar if you go this route.

Make the Hot Ice

What you are going to do is make a supersaturated sodium acetate solution. The solution will remain a supercooled liquid until a little solid sodium acetate is introduced. This will cause rapid crystallization that will resemble a block of ice, except it will be hot to the touch and not edible.

  1. Dump some sodium acetate monohydrate into a saucepan.
  2. Add just enough water to dissolve the sodium acetate.
  3. Heat the solution to just below its boiling point.
  4. Stir in more sodium acetate. Keep stirring and adding sodium acetate until you start to see solid material accumulating at the bottom of the pan.
  5. Pour the hot solution into a glass or other container. Do not allow any of the undissolved solid to enter the container.
  6. Cool the solution in the refrigerator 30 minutes to an hour.
  7. Remove the solution from the refrigerator. As long as you didn't leave any solid sodium acetate in the solution, it should still be liquid.
  8. When you are ready to make 'ice' introduce a little of the solid sodium acetate. You could dip a toothpick or the edge of a spoon in sodium acetate powder.
  9. The crystallization will evolve heat (exothermic reaction), making the solid feel hot to the touch (~130° F).

Hot Ice Trick

You don't have to solidify the sodium acetate in a dish. You can crystallize it as the solution is being poured to make fantastic shapes.

Comments

January 7, 2009 at 8:58 pm
(1) IQLion says:

Can you will tell how to make it still liquid?

July 27, 2011 at 11:02 pm
(2) pragati says:

dont you like melt it

January 25, 2009 at 8:16 pm
(3) brandon says:

Can u boil it and then cool it down again to make it cause the reaction to produce heat multiple times?

October 31, 2011 at 9:34 pm
(4) ladasha watson says:

you can because when u melt it it become solid

February 5, 2009 at 10:57 pm
(5) science gy says:

Yes, you can reheat it to resupersaturate the liquid again.

February 11, 2009 at 7:55 am
(6) quinton says:

can you leave me the investigation plan?

February 19, 2009 at 7:19 pm
(7) Hannah says:

Hii thank you so much for this experiment now I can have an interesting fun science fair! :)

November 9, 2011 at 9:10 pm
(8) bob (i aint tellin u my real name) says:

ikr i b doin this fo my sci. fair project 2

March 10, 2009 at 9:36 am
(9) enforc says:

how long will the hot ice last? (before it melts, evaporates, whatever they do.)

April 21, 2009 at 4:17 am
(10) Nina4593 says:

hye!!! can you tell me what is the problem statement of this experiment(hot ice)???

April 23, 2011 at 4:21 pm
(11) sham12287 says:

I think, no problem there. The problem is what is hot ice??haha!

April 29, 2009 at 7:56 pm
(12) Meltice says:

That was crazy that was just the best chemical reaction i ever seen. It just built up like clay. If i did that at my science fair this year at y school i would not come in second place like i did last year.!

October 14, 2009 at 6:36 pm
(13) roy mccallister says:

thanks for the experiment idea i did it and got a 1st place ribbion in the science fair it was fun to do.

November 3, 2009 at 10:56 am
(14) heather says:

can you explain how the commercial handwarmers work? ie how does clicking the metal disk start the reaction?

November 8, 2009 at 8:31 pm
(15) dav says:

what is its boiling point

November 17, 2009 at 2:56 pm
(16) fluffybunnyishappy@yahoo.com says:

i like it except for the fact that it is hot and i wanted it cold instead of hot because someone can get burned and it will hurt and they will say OW! and start crying and sue for everything you have and leave you starving on the street begging for money and love

December 2, 2009 at 6:28 pm
(17) jejejejeje125 says:

Cool experiment but the problem is making the sodium acetate… I would recommend it as a home project. Not for a science fair project!!!!!
not enough info on this project
THANKS ANYWAY

January 10, 2010 at 4:52 pm
(18) aj says:

ty so much

January 27, 2010 at 2:45 pm
(19) john east says:

you are so hot anne luv u!!!!!!!!!!!!!!!!

February 16, 2010 at 9:12 pm
(20) EdwardCullenLover#1 says:

Well yhis project sounds cool. So im going to try it for my science projent! thank u so much for the project :)

May 6, 2011 at 2:48 pm
(21) josh says:

i want to make this

February 16, 2010 at 9:19 pm
(22) EdwardCullen#1 says:

well so far im sorry for the miss spellings as in yhis = this,projent = project :( , but its ok because i love this projent:)

February 26, 2010 at 6:34 pm
(23) BeckyM says:

Well, my project is due in a few days and I choose to do hot ice, my science teacher is really interested to see it this Monday, well I better go finish it up.

I do know how to make sodium acetate. If you ever found one using a microwave and another using a stove, just use the stove, the microwave makes it bubble over and mine came out as an yellow lump.

June 23, 2010 at 8:04 am
(24) maronette says:

thank you for the project…

October 23, 2010 at 12:26 am
(25) marilyn says:

hi! can u tell me what is the problem statement of this hot ice and the significance of the study?i really need it for my project today

February 6, 2011 at 2:13 am
(26) gerald says:

can you tell me what is the problem for this experiment(hot ice)?

March 18, 2011 at 4:50 am
(27) madz says:

can you upload the tutorial video of hot ice

March 24, 2011 at 9:24 pm
(28) bob125 says:

hi! I was ask about the sodium acetate where do you get it and how much is it?

September 16, 2011 at 12:12 pm
(29) shelby says:

from walmart

July 27, 2011 at 11:00 pm
(30) pragati says:

well is there any OTHER info on hot ice. hello science fair project due in 2 daYS

August 3, 2011 at 9:39 am
(31) amrit says:

its good project but give some more details about it

August 1, 2012 at 12:46 pm
(32) Jeryll says:

Can you give me answer for the nature of physical and chemical equilibrium

January 8, 2013 at 7:55 pm
(33) Anya Rubi says:

how long do you wait for the sodium acetate untill you touch it to make Hot Ice and do you need a parent? and what type of pan or saucer?? LOL?!

February 8, 2013 at 8:29 pm
(34) Rob says:

Can you recharge sodium acetate without using boiling water?

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