01 March 2025

When you microwave an ice cube...


... the results are somewhat unexpected.

I had heard that solid ice does not respond to microwaves the way water does, so today while boiling some water for ramen, I also put in the (standard suburban) microwave one ice cube (with a paper towel to catch any meltwater).

The paper towel was unnecessary.  After 2 1/2 minutes the water in the measuring cup was in a full rolling boil, but the ice cube was ice cold.  There wasn't even a drop of water on the towel beneath.

Posting this so readers can use the info to win bar bets or impress your children at dinner.  Or perhaps next time you host a party ask guests to guess "how quickly" will the microwave melt the ice cube.  

Addendum:  several interesting observations in the comment thread.

Related:  Microwaving Ice - why defrosting is so slow.  Note: "This is why you shouldn't defrost a chicken on full power..."

13 comments:

  1. Can we go back to why you would ever microwave water for ramen (or tea, or whatever)?

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    Replies
    1. It's a convenient way to get water boiling. Any reason not to?

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  2. Long time follower, first time poster: I don't know how I've made it 42 years without hearing of this! Of course, I emptied my ice cube trays last week to make room for a bunch of stock. Can't wait to try!! (And thank you for the wonderful blog)

    Cheers from Boise :)

    Sarah

    ReplyDelete
    Replies
    1. Greetings, Sarah. Lurkers make up the majority of TYWKIWDBI readership. Glad you're here.

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    2. And please know that the loudmouths here are lurkers on other forums....

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  3. Good trick for my grandson

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  4. Ok scientist mind blown. Had to test immediately.

    The ice will melt. After 4 minutes, my ice cubes were gone and I had a moist towel left. I suspect a lot of the ice may have sublimated, straight to water vapor.

    But it is true that the "ice" molecules lack the mobility to react to the oscillating electric field that heat the "liquid" molecules by making their little dipoles follow the oscillating field. For that they have to turn around a lot and really fast which means they have to move and that causes them to warm up. The field kinda makes them do jumping jacks which we all know makes us hot.

    https://www.thenakedscientists.com/get-naked/experiments/microwaving-ice-why-defrosting-so-slow

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  5. Paul in JacksonvilleMarch 2, 2025 at 12:23 PM

    I'm like Sarah. I tried this with two cubes, on a paper towel, on a glass salad plate. Thirty seconds, and the cubes melted about half way. Does this only work if there is something else being nuked, too?

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  6. but why? is the bond frequency of soli water no longer in the microwave range?

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  7. Thank you, guys. I'm not at all surprised that some readers here took up the challenge and tested my results.

    After reading Paul's comment I decided to retry the experiment with two ice cubes without the measuring up of water in the microwave (?did it "absorb" the microwaves and protect the ice?)

    After 30 seconds the ice cubes appeared pristine (as viewed through the screen). Same at 1 minute. But by 1:30 there was moisture on the towel, and at 2:30 there was significant melting. As I took them out, the puddle around the ice cubes was hot to the touch.

    So, putting on my English Major cap, I modified the post to eliminate the phrase "nothing happens," substituting "unexpected," and referred future readers to the Comments thread.

    Now I have my Retired Scientist cap on and will read the interesting link Nepkarel found.

    ReplyDelete
    Replies
    1. Back again. Nepkarel's link added to the body of the post. I'm guessing that the variable response times depend in part on the initial state of the ice and the ambient temperature of the room/microwave chamber. Solid ice is resistant to the effects of microwave, but if there are any "soft" areas in the ice or if ambient air creates a microfocus of liquid on the surface of the cube, those areas will heat rapidly. Maybe my being in Madison, Wisconsin and Paul being in Jacksonville was a significant variable.

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  8. Looking forward to sharing this with tweens & teens I know. Thanks.

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  9. What's a little puzzling to me is that I routinely (daily) put hard-frozen foods into the microwave to cook for meals, without any problems. But the link notes not to defrost a large item using microwaves because of nonuniformity problems. I guess the "peel back plastic and stir" instructions on the power bowls midway through the session take care of that problem.

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