# Water expands if you freeze it... or heat it? **URL:** \ **Category:** Factual Questions\ **Created:** [February 19, 2005, 6:26pm UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918 "2005-02-19T18:26:41Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Kythereia](https://avatars.discourse-cdn.com/v4/letter/k/e8c25b/32.png) [@Kythereia](https://boards.straightdope.com/u/Kythereia)\ **Post date:** [February 19, 2005, 6:26pm UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/1 "2005-02-19T18:26:41Z")
I was surfing around [moviemistakes.com](http://www.moviemistakes.com/) just now (a good way to waste some time 🙂 ) and found this quote on the X-Men 2 movie: > [@](#): > > When Bobby freezes the coffee in the cup, he manages to defy physics and prevent the frozen liquid from expanding at the same time. OK, all cool. But then a correction from another user: > [@](#): > > [Speaking as an ex-chemistry teacher: water is really weird. It expands if you cool it to the freezing point OR IF YOU HEAT IT. That is, the frozen tea, and the very hot tea, might be the same amount LARGER than lukewarm tea. It’s perfectly plausible that hot tea could occupy the same volume as frozen tea, although I haven’t checked the coefficient of thermal expansion for tea to be sure.] I don’t get it. 😕 Is (s)he right? ---
**Author:** ![Dr.Lao](https://avatars.discourse-cdn.com/v4/letter/d/2bfe46/32.png) [@Dr.Lao](https://boards.straightdope.com/u/Dr.Lao)\ **Post date:** [February 19, 2005, 6:34pm UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/2 "2005-02-19T18:34:16Z")
It depends on the ice you’re forming, but under normal atmospheric conditions water has a maximum density at around 4 C. From that point, it will expand either on heating or cooling (to a point). ---
**Author:** ![audiobottle](https://avatars.discourse-cdn.com/v4/letter/a/bc8723/32.png) [@audiobottle](https://boards.straightdope.com/u/audiobottle)\ **Post date:** [February 19, 2005, 6:35pm UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/3 "2005-02-19T18:35:55Z")
Water does expand when it’s frozen. The way the molecules settle together actually has a greater volume than when it’s in liquid state; that’s why ice floats. It will also expand if you heat it, since you’re imparting more energy to the molecules and they’re bouncing around more, creating a larger volume. As for the movie, I really can’t say. If I remember correctly, he freezes the cup as well, and it happens really quickly. So if anything, I’m surprised the cup didn’t break just from the stress induced by going from hot to cold in such a short time. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [February 19, 2005, 6:48pm UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/4 "2005-02-19T18:48:23Z")
In simple terms, everything expands when you heat it and contracts when you cool it. However, water is a special case that basically does that **but in addition** …when it freezes its molecules form a crystal structure that takes up more room than the liquid water did a few degrees above freezing. The expansion from this crystallization effect overrides the normal contraction from its getting colder. ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [February 19, 2005, 6:59pm UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/5 "2005-02-19T18:59:00Z")
> [@Kythereia](#): > > I don’t get it. 😕 Is (s)he right? As mentioned, water, like pretty much anything else, expands when heated. Of course, it also expands when it freezes, I think the minimum point (max density)is just over 0 degrees C. Now, the teacher is dead wrong in thinking that hot tea might be the same density as ice. This is trivially tested by putting an icecube in boiling hot water. \ ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [February 19, 2005, 7:08pm UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/6 "2005-02-19T19:08:43Z")
Tested… ice floats in boiling hot water, therefore, ice should take up more space than hot tea. Gee, didn’t need to break out those pesky coefficients of expansion to figure this out. Could have relied on personal experience, but a nice fresh test is always worth it. ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [February 19, 2005, 7:24pm UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/7 "2005-02-19T19:24:03Z")
Doesn’t water expand due to gases in solution? Can we make a water with nothing in solution that wouldn’t expand? ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [February 19, 2005, 7:47pm UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/8 "2005-02-19T19:47:20Z")
> [@Cheesesteak](#): > > Tested… ice floats in boiling hot water, therefore, ice should take up more space than hot tea. > > Gee, didn’t need to break out those pesky coefficients of expansion to figure this out. Could have relied on personal experience, but a nice fresh test is always worth it. Well, to be fair, most ice cubes contain a significant amount of voids (frozen air bubbles) that make it less dense still, but yes, water ice (and liquid water below 4[sup]o[/sup]C) expands rather than contracts. This is unusual, and for us, very fortunate, because it means that frozen water (ice) stays on the top of a pond, insulating the thermal mass of the water and creating convection currents that probably had a fair amount to do with life being created and maintained waybackwhen. Water behaves this way because of the dipole nature of the H[sub]2[/sub]O molecule, which changes its angle from about 104.5[sup]o[/sup] when fluid (liquid or gas) to around 108[sup]o[/sup] when solid. The reasons it does this are very complex and beyond my grasp of electrochemistry to explain clearly, but this is what causes water ice to float, and what leads to the hexigram shape of water crystals, as explained [here](http://www.science.ca/askascientist/viewquestion.php?qID=41). I believe water is the only “simple” molecule that does this, although I’m morally certain that many of the complex organic polymers show these kinds of properties. Perhaps some chemist Doper will come along and clarify/correct/vilify my explaination. There’s quite a good book about the interesting properties and history of water; [Life’s Matrix: A Biography of Water](http://www.amazon.com/exec/obidos/tg/detail/-/0520230086/qid=1108843164/sr=8-1/ref=sr_8_xs_ap_i1_xgl14/002-4024994-3198403?v=glance&s=books&n=507846) by Philip Ball, that you might want to check out if you are interested on the topic. Stranger ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [February 19, 2005, 7:54pm UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/9 "2005-02-19T19:54:37Z")
> [@Stranger On A Train](#): > > Well, to be fair, most ice cubes contain a significant amount of voids (frozen air bubbles) that make it less dense still, but yes, water ice (and liquid water below 4[sup]o[/sup]C) expands rather than contracts. This is unusual, and for us, very fortunate, because it means that frozen water (ice) stays on the top of a pond, insulating the thermal mass of the water and creating convection currents that probably had a fair amount to do with life being created and maintained waybackwhen. > > Water behaves this way because of the dipole nature of the H[sub]2[/sub]O molecule, which changes its angle from about 104.5[sup]o[/sup] when fluid (liquid or gas) to around 108[sup]o[/sup] when solid. The reasons it does this are very complex and beyond my grasp of electrochemistry to explain clearly, but this is what causes water ice to float, and what leads to the hexigram shape of water crystals, as explained [here](http://www.science.ca/askascientist/viewquestion.php?qID=41). > > I believe water is the only “simple” molecule that does this, although I’m morally certain that many of the complex organic polymers show these kinds of properties. Perhaps some chemist Doper will come along and clarify/correct/vilify my explaination. There’s quite a good book about the interesting properties and history of water; [Life’s Matrix: A Biography of Water](http://www.amazon.com/exec/obidos/tg/detail/-/0520230086/qid=1108843164/sr=8-1/ref=sr_8_xs_ap_i1_xgl14/002-4024994-3198403?v=glance&s=books&n=507846) by Philip Ball, that you might want to check out if you are interested on the topic. > > Stranger And the great majority of the expansion comes in the transition from liquid at 0 C to solid at 0 C. My source gives the specific gravity of water at 4 C as 1.0000; at 0 C 0.9999 (liquid); and at 0 C (solid) 0.9150 ---
**Author:** ![audiobottle](https://avatars.discourse-cdn.com/v4/letter/a/bc8723/32.png) [@audiobottle](https://boards.straightdope.com/u/audiobottle)\ **Post date:** [February 20, 2005, 1:42am UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/10 "2005-02-20T01:42:56Z")
> [@Balthisar](#): > > Doesn’t water expand due to gases in solution? Can we make a water with nothing in solution that wouldn’t expand? To answer your question, no, you couldn’t make water that doesn’t expand when heated. Say you have a glass of pure H[sub]2[/sub]O. Each of those molecules are bouncing around a bit. As you heat up the water, you’re imparting more energy to those molecules. They start to bounce around with more speed, thus widening the area around each individual. Think of a 250 lb football player at a folk show. Maybe he’s swaying side to side a little, but on the whole, the people can pack in pretty tight there. Now put him at a Tool show. The harder he starts to mosh, the more space is going to clear around him. So the overall “volume” of the crowd expands, just as the overall volume of the water expands. If there are gases dissolved in the water, like CO[sub]2[/sub] or something, those will also expand and probably cause the overall volume to increase, but the precise effect is complicated due to the interactions of two different molecules. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [February 20, 2005, 2:09am UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/11 "2005-02-20T02:09:36Z")
> [@Stranger On A Train](#): > > … > I believe water is the only “simple” molecule that does this, although I’m morally certain that many of the complex organic polymers show these kinds of properties. > … > Stranger Elemental gallium displays the behavior of expanding on transition from liquid to solid. Since the freezing point is just above room temperature, this is actually a consideration in the storage of the stuff. ---
**Author:** ![Enderw24](https://avatars.discourse-cdn.com/v4/letter/e/ba9def/32.png) [@Enderw24](https://boards.straightdope.com/u/Enderw24)\ **Post date:** [February 20, 2005, 2:16am UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/12 "2005-02-20T02:16:48Z")
> [@Cheesesteak](#): > > Tested… ice floats in boiling hot water, therefore, ice should take up more space than hot tea. . One doesn’t necessarily conclude the other. Another rationale is that the force of rising air bubbles in boiling water is great enough to overcome the weight of an ice cube, therefore keeping it afloat. ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [February 20, 2005, 2:46am UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/13 "2005-02-20T02:46:58Z")
Okay, I knew that the crystals in frozen water take up more room than liquid water does. I didn’t know they were “approximately tetrahedral crystals that give the characteristic hexagonal shape to ice crystals,” until I looked at **Stranger’s** link. However, one of my nephews once asked me a question about those expanded crystals that I still can’t answer. He wanted to know. **"What fills those teensy spaces in the crystals?"** ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [February 20, 2005, 2:49am UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/14 "2005-02-20T02:49:19Z")
> [@AskNott](#): > > **"What fills those teensy spaces in the crystals?"** Electric and magnetic fields? ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [February 20, 2005, 3:26am UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/15 "2005-02-20T03:26:24Z")
> [@Enderw24](#): > > Another rationale is that the force of rising air bubbles in boiling water is great enough to overcome the weight of an ice cube, therefore keeping it afloat. The water was just off the boil, rather than currently boiling, just like a fresh cup of hot tea 5 seconds before the teabag is added. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [February 20, 2005, 4:13am UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/16 "2005-02-20T04:13:04Z")
> [@AskNott](#): > > Okay, I knew that the crystals in frozen water take up more room than liquid water does. I didn’t know they were “approximately tetrahedral crystals that give the characteristic hexagonal shape to ice crystals,” until I looked at **Stranger’s** link. However, one of my nephews once asked me a question about those expanded crystals that I still can’t answer. He wanted to know. **"What fills those teensy spaces in the crystals?"** We recently had a very entertaining discussion about this, re: [Why can’t my hand go through my desk?](http://boards.straightdope.com/sdmb/showthread.php?t=299054). I think the most relevent posts to your question are [here](http://boards.straightdope.com/sdmb/showpost.php?p=5771301&postcount=33) and [here](http://boards.straightdope.com/sdmb/showpost.php?p=5779100&postcount=43). Short Answer: it’s all space that’s filled up with fields. Long Answer: Start with **Introduction To Modern Physics** and **Introductory Electrochemistry** and go on from there. Stranger ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [February 20, 2005, 6:42am UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/17 "2005-02-20T06:42:57Z")
> [@audiobottle](#): > > To answer your question, no, you couldn’t make water that doesn’t expand when heated. Say you have a glass of pure H[sub]2[/sub]O. Each of those molecules are bouncing around a bit. As you heat up the water, you’re imparting more energy to those molecules. Hmmm… sorry to have induced you into making such an obvious answer. I meant _freezing_ the water, since I imagined that we were all in general agreement that virtually everything expands when heated. My bad. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [February 20, 2005, 6:53am UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/18 "2005-02-20T06:53:36Z")
> [@Balthisar](#): > > Hmmm… sorry to have induced you into making such an obvious answer. I meant _freezing_ the water, since I imagined that we were all in general agreement that virtually everything expands when heated. My bad. I don’t think I understand your question. Water contracts, slightly, between 0[sup]o[/sup] and (roughly) 4[sup]o[/sup] at standard atmospheric pressure, and then goes on to behave like a perfectly normal substance after that. This is due to its peculiar molecular configuration, and has nothing to do with gases in solution (though gases in solution will resolve out as water transitions into solid state, resulting in the voids that makes most ice translucent. Ice without inclusions or bubbles is clear (slightly blueish, actually), but is still buoyant in liquid water. Stranger ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [February 20, 2005, 8:33am UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/19 "2005-02-20T08:33:37Z")
> [@Enderw24](#): > > One doesn’t necessarily conclude the other. Another rationale is that the force of rising air bubbles in boiling water is great enough to overcome the weight of an ice cube, therefore keeping it afloat. Those aren’t air bubbles. Those are water vapor bubbles. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 20, 2005, 8:12pm UTC](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918/20 "2005-02-20T20:12:12Z")
To be fair, we don’t know just how cold that tea-ice was. After it freezes, ice, like most substances, will contract with lowering temperatures. So is there any sufficiently low temperature (at standard pressure) where ice would have the same density as hot water? [Next page](https://boards.straightdope.com/t/water-expands-if-you-freeze-it-or-heat-it/290918.md?page=2)