# Silly, but liquids into solids in heat? **URL:** \ **Category:** Factual Questions\ **Created:** [December 16, 2002, 11:52pm UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200 "2002-12-16T23:52:26Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![HubZilla](https://avatars.discourse-cdn.com/v4/letter/h/ccd318/32.png) [@HubZilla](https://boards.straightdope.com/u/HubZilla)\ **Post date:** [December 16, 2002, 11:52pm UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/1 "2002-12-16T23:52:26Z")
A silly question I asked in elementary school never got answered, and although it may still seem silly, I gotta know. No snickering, please! In first grade, we were taught that solids turn to liquids if heated enough. So my question was “what about a cake?” The batter is a thick liquid, but becomes a solid if heated. If you heat it too much, it becomes a harder solid. Now I know a cake does not violate physics, but why does it get harder? My guess is the liquid part is boiled away, turned to steam, and the hard part is all that’s left? ---
**Author:** ![cmkeller](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmkeller/32/118_2.png) [@cmkeller](https://boards.straightdope.com/u/cmkeller)\ **Post date:** [December 16, 2002, 11:53pm UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/2 "2002-12-16T23:53:58Z")
Your guess is correct, HubZilla. ---
**Author:** ![Giraffe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giraffe/32/129_2.png) [@Giraffe](https://boards.straightdope.com/u/Giraffe)\ **Post date:** [December 17, 2002, 12:25am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/3 "2002-12-17T00:25:46Z")
Actually that’s not correct. If it were, you could bake a cake by leaving it out on the counter for a couple of days. The reason the cake gets solid is due to the presence of polymers in the batter. (I’m not sure which ingredient is key here, maybe the eggs.) Heating them up past a given temperature allows them to wiggle around and connect with other polymers. Once enough connections form, it solidifies. The degree to which the polymers cross-link greatly affects the consistency (hence the texture of overdone cake) – this is also why you don’t want to stir or knead some batters and doughs too much – too many connections form and it gets hard or crunchy. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [December 17, 2002, 12:46am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/4 "2002-12-17T00:46:17Z")
By polymers, you mean proteins, don’t you? The expansion of starches also plays a part, as does loss of moisture. ---
**Author:** ![cmkeller](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmkeller/32/118_2.png) [@cmkeller](https://boards.straightdope.com/u/cmkeller)\ **Post date:** [December 17, 2002, 1:17am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/5 "2002-12-17T01:17:52Z")
Giraffe: > [@](#): > > Actually that’s not correct. If it were, you could bake a cake by leaving it out on the counter for a couple of days. The batter would still get solid if you tried that. But the product isn’t something you’d want to eat due to mold, bacteria and/or staleness. ---
**Author:** ![Giraffe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giraffe/32/129_2.png) [@Giraffe](https://boards.straightdope.com/u/Giraffe)\ **Post date:** [December 17, 2002, 1:33am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/6 "2002-12-17T01:33:45Z")
I think I mean polymers, but I could be wrong. (This is well outside my area of expertise, in that I don’t cook and I’m bad at biology.) Solidification during cooking was the example given to me by a physicist who worked on cross-linking polymers. His favorite example was Jell-o. Pudding is another good one, I believe. ---
**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:** [December 17, 2002, 1:39am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/7 "2002-12-17T01:39:35Z")
The key is that melting ice is just a phase change, but baking a cake is a chemical change. Cake batter is not just melted cake (or antimelted, or whatever), it’s an entirely different substance. And I think that the primary source of the polimers is the flour, not the eggs, since there are eggless bread recipes. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [December 17, 2002, 1:50am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/8 "2002-12-17T01:50:51Z")
ALso depending on pressure and temp you could have something go from liquid to solid when heated (I think). I seem to remember something like this in theromdynamics. The cake changes chemically ---
**Author:** ![Lostboy](https://avatars.discourse-cdn.com/v4/letter/l/f9ae1b/32.png) [@Lostboy](https://boards.straightdope.com/u/Lostboy)\ **Post date:** [December 17, 2002, 2:07am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/9 "2002-12-17T02:07:09Z")
Proteins are examples of polymers so you are both right. As was explained earlier, baking a cake is a complex chemical reaction primarily between the various proteins in the flour, sugar, and water. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [December 17, 2002, 2:17am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/10 "2002-12-17T02:17:40Z")
Please correct me if I’m wrong, but I’ve been under the impression that the phase shifting (Solid-Liquid-Gas) rules are really only meant for the Elements. Sure, they may apply to more complex chemicals, but all Elements have a Solid, Liquid, or Gas state depending upon temperature and pressure. Once the elements start gettin’ jiggy with each other, all bets are off… (yes, i said “jiggy”) -kev ---
**Author:** ![bbeaty](https://avatars.discourse-cdn.com/v4/letter/b/c0e974/32.png) [@bbeaty](https://boards.straightdope.com/u/bbeaty)\ **Post date:** [December 17, 2002, 2:44am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/11 "2002-12-17T02:44:07Z")
Some materials melt when heated, but others react chemically before they get hot enough to melt. You could TRY to melt a piece of cake, but it would turn into charcoal and water vapor first. Also, some solids evaporate when heated (they never melt at all.) I think carbon is one of these, so even if you tried melting the charcoal left behind from the cake-melting experiment, it would get red hot and then evaporate. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [December 17, 2002, 2:55am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/12 "2002-12-17T02:55:50Z")
**bbeaty** , you’d need to heat your charcoal in the absence of oxygen, to prevent it reacting chemically first. You’d also need some specialised equipment. Carbon sublimes (from memory) somewhere above 3500 K. I don’t have the databook handy. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [December 17, 2002, 3:57am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/13 "2002-12-17T03:57:37Z")
…but it’s very easy to see dry ice sublime. And, IIRC, Helium is predicted to be one of the only elements that will never have a solid phase, even at 0K (even Hydrogen can form a solid in a diamond anvil and under enough pressure). But I may be mistaken… ---
**Author:** ![HighSoci](https://avatars.discourse-cdn.com/v4/letter/h/ba8739/32.png) [@HighSoci](https://boards.straightdope.com/u/HighSoci)\ **Post date:** [December 17, 2002, 4:02am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/14 "2002-12-17T04:02:18Z")
So why does an egg turn to a solid when it is heated and don’t evaporate? ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [December 17, 2002, 4:08am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/15 "2002-12-17T04:08:44Z")
Baking a cake is more complex than you could imagine scientifically. More than you ever wanted to know about this subject [THE CHEMISTRY OF CAKES](http://www.margarine.org.uk/pg_app2.htm) ---
**Author:** ![bbeaty](https://avatars.discourse-cdn.com/v4/letter/b/c0e974/32.png) [@bbeaty](https://boards.straightdope.com/u/bbeaty)\ **Post date:** [December 17, 2002, 4:30am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/16 "2002-12-17T04:30:30Z")
> [@](#): > > bbeaty, you’d need to heat your charcoal in the absence of oxygen, to prevent it reacting chemically first. No, heat the _cake_ in the absence of oxygen. I was talking about attempts to melt some solidified bread/cake. Try to melt a cake in air and you’re left with a tiny bit of ash plus lots of CO2 and H2O clouds. So do it under nitrogen so you just get charcoal: chemistry happens rather than melting, oxy or no oxy. ---
**Author:** ![Giraffe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giraffe/32/129_2.png) [@Giraffe](https://boards.straightdope.com/u/Giraffe)\ **Post date:** [December 17, 2002, 5:11am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/17 "2002-12-17T05:11:58Z")
**astro** , great link! This thread got me interested in the problem, but my own Google searches turned up nothing. **Anthracite** , you’re right, but only with the caveat of “at ambient pressure”. Because helium is both light and inert, quantum motion prevents freezing even at T=0 K. Helium does have a solid phase (my first published paper was on solid helium), but only under pressure. Here is the [phase diagram](http://boojum.hut.fi/research/theory/helium.html) of helium. I’m a little shaky on cake physics, but helium I know. 🙂 ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [December 17, 2002, 5:54am UTC](https://boards.straightdope.com/t/silly-but-liquids-into-solids-in-heat/143200/18 "2002-12-17T05:54:19Z")
HighSoci, eggs coagulate because the heat breaks up the protein structure of the raw egg, and a new structure forms. The first kind of protein happens to be liquid, the new structure is solid.