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First of all, I'm genuinely sorry if this question isn't "serious" enough for this forum!

A common cliche in movies and tv is that a very tough object (eg the villain) is frozen, and then hit with something, shattering into a million pieces.

I've seen a demo of a flower being put into liquid nitrogen, then being crumbled, but a flower is a very delicate object to start off with. If I take a leg of lamb (for example) out of the freezer, I don't feel like it's in any danger of shattering into a million bits (unlike my foot if i were to drop it).

So, is the whole "cold = brittle" thing just movie bullcrap? Or is there anything to it? Sticking with the leg of lamb example: is there a temperature to which a leg of lamb could be dropped that would make the leg of lamb prone to shattering?

EDIT - i just realised that the question title could be read as "Is there anything which is rendered extremely brittle by extreme cold?". Obviously there are some things, eg flowers. Hence the title change.

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  • $\begingroup$ Great question! I have no idea about the answer, but would love to be educated. $\endgroup$ – Danu Aug 13 '14 at 11:33
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    $\begingroup$ What makes you think a leg of lamb wouldn't shatter at liquid nitrogen temperatures? Your freezer is cold but liquid nitrogen is a lot colder and there's no guarantee that the behaviour will be the same. $\endgroup$ – Emilio Pisanty Aug 13 '14 at 11:34
  • $\begingroup$ @Emilio - That was just my hunch (hence "i don't feel like..."), but i don't know: that's why i'm asking. Feel free to set me straight with some facts. :) $\endgroup$ – Max Williams Aug 13 '14 at 11:40
  • $\begingroup$ This gives a good start - for metals and wooden objects (I assume that it indeed works on all organic matter, having seen Emilio's link) van.physics.illinois.edu/qa/listing.php?id=1683 $\endgroup$ – Danu Aug 13 '14 at 11:49
  • $\begingroup$ @EmilioPisanty - i just noticed your youtube link, sorry. Hmm, looks like a heart becomes brittle at least. A heart is made of muscle fibers which i'd expect to provide some reinforcement, so that's encouraging for the "yes everything becomes brittle" camp (and screenwriters). $\endgroup$ – Max Williams Aug 13 '14 at 12:39
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As far as I remember, yes, everything becomes brittle at low enough temperatures. This is due to the brittle-to-ductile transition (BDT - or sometimes referred to in reverse as DBT, ductile-to...). This transition is temperature dependent (amongst others (strain-rate ...)). Can every composition actually reach low enough temperatures, or do some have a transition temperature below 0K. This is also pressure- and state-dependent. Also, the BTD applies to solids.

One thing to keep in mind though, is that dense things become very hard to break, like a leg of lamb or a banana. A sufficiently frozen banana (liquid nitrogen) will break, but it requires a lot of force. Simply dropping it from a meter or two will not shatter it. It needs to be thrown or hit with something harder. Yes, I have tried this. The bigger it is, the more force it would require. I can shatter any boulder for you, but you may not have the size of hammer I would need ...

Having said that, most biological matter/tissue is mostly water, so freezing the mentioned examples would result in some form of ice. At least something that should behave similarly to ice. The DTB-transition applies generally, like for your desk or computer.

As far as I know, the BTD-transition is not completely understood. I don't think I have my lecture notes anymore, and it is a while since I took a class on this, so I would start with Wikipedia, but you would soon end up in scientific papers, I think.

In essence, brittle fracture is due to direct bond breaking resulting in cleavage. Ductile fracture is due to microvoid growth and coalescence. Temperature sort of maps to time and information transfer. At high temperatures, particles/dislocations travel quicker and with more ease than at lower temperatures. Thus information (stress, strain, ...) travels through the sample. There is more time to move around and shift to try to alleviate the applied stress or strain. So, there is time to form microvoids and lots of stretching. These voids will grow and eventually join with neighbouring voids and so the fracture will advance.

At low temperatures, many or all of the ductile mechanisms do not have time to come into play, and at the extreme, fracture is locally advanced through the breaking of the weakest bonds.

In the DTB-transition zone, both mechanisms are present. As these mechanisms are very basic and general, I think that any material should undergo such a transition (assuming transition temperature above 0K). Of course with a varying fracture toughness and ... "shatterability".

Note: These are educated guesses at best, I have not done any calculations or simulations on this.

@MaxWilliams Firstly, this person would already be dead as all body functions would have ceased, but that's not really relevant to the question.

Now, a person is quite large, so you would need a lot of energy, preferrably concentrated. Explosives would do it (and other things), but you asked for handguns. I can not realistically imagine any handgun to do this. One point is that I think that the energy from the bullet would be dissipated in the dense body.

Another point is that the shape of a person is quite stretched (not spherical) so what you are asking for is bonds that will separate with relative ease as well as distributing energy transversally. I am assuming a shot to the torso. Maybe an extremely powerful handgun could penetrate all the way through, maybe a hollowpoint or some specially designed bullet would create more explosive damage, but in the end, I think that the target is quite comparable to a stone (maybe ice) statue, and I do not think that would be shattered that easily. Definitely not like in the movies.

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  • $\begingroup$ Do you think that a frozen person, for example, might shatter into a million pieces when hit with a bullet fired from a handgun? Is there a rough temperature they would need to be reduced to? And is it possible to reduce them to this temperature by spilling liquid nitrogen or anything else on them? $\endgroup$ – Max Williams Aug 13 '14 at 13:38
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    $\begingroup$ Could you perhaps expand the answer to actually cover the relevant physics to understand this phenomenon? $\endgroup$ – Danu Aug 13 '14 at 13:57
  • $\begingroup$ @MaxWilliams Probably, but I expect they would be dead from being frozen first. You'd probably need a bath of liquid nitrogren or something to freeze them all the way through to. $\endgroup$ – nivag Aug 13 '14 at 15:53
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    $\begingroup$ I have tried this too with a potato (frozen in an ordinary household freezer). A drop from between 3 and 4 meters did little to damage the potato but being thrown downwards from the same height shattered quite spectacularly. As I remember, there weren't enough large pieces left to merit a clean up. $\endgroup$ – NeutronStar Aug 13 '14 at 20:16
  • $\begingroup$ Edited in response to question by @MaxWilliams $\endgroup$ – Knut Gjerden Aug 14 '14 at 8:00
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Many organic substances will become brittle at the temperature of liquid nitrogen, but there are plenty of material choices left for e.g. vacuum seals, pipes, containers, etc., which are not. Indeed, we have constructed entire rocket fuel systems at the temperature of liquid hydrogen, which retain most of their mechanical properties. If you go down further, helium stays liquid above a pressure of 2.5 MPa (25bar) even near absolute zero. Obviously, a liquid can't shatter, so lowering the temperature is not enough to make "everything" shatter.

As for the villain in movies... he was done when his body froze below 0 degrees C, of course, the rest is just a movie joke.

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    $\begingroup$ As another example, superconducting magnets are usually housed in austenitic stainless steels, many of which retain all of their strength and most of their ductility and fracture toughness at least as far as 1.8 K, which is the temperature of many of the LHC magnets. So no shattering there. How exactly ductility can occur when there is virtually no thermal energy available for the atoms to rearrange themselves to relieve the stress at the tip of a crack, I cannot tell you. $\endgroup$ – akrasia Aug 13 '14 at 21:51
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    $\begingroup$ @akrasia: those are very good examples. I would venture to guess, that quantum mechanics comes to the rescue. It always provides a non-trivial amount of kinetic energy to the ground state. The proper question would probably be, what's the quantum mechanical creep time for a given material at 0K? For many materials it may approach the age of the universe, of course, while for liquid helium, it's just the opposite, and it's a very happy liquid thanks to its ground state energy. $\endgroup$ – CuriousOne Aug 13 '14 at 22:03
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    $\begingroup$ Hmm, thanks. So it seems (from consensus) that organic matter will become brittle and prone to shattering at low temperature, but there are plenty of non-organic materials which don't display this behaviour. $\endgroup$ – Max Williams Aug 14 '14 at 8:31
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    $\begingroup$ re the villain, though: often these characters have supernatural powers, and might survive just being frozen. Hence the need for the coup-de-grace shatter from the hero. $\endgroup$ – Max Williams Aug 14 '14 at 8:32
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    $\begingroup$ Truth to be told, supernatural powers are outside of the responsibility of physicists, and we are glad, that the scriptwriters are taking care of them. ;-) $\endgroup$ – CuriousOne Aug 14 '14 at 18:23
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Things like flower and lamb leg become brittle because of large portion of water contained in them. Water gets frozen into ice upon cooling, which is brittle. Basically, brittleness is related to the directionality of chemical bonds. Materials form by more directional bonds tend to be more brittle. Meanwhile, they tend to be harder.

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Great answer found here:

Ductile and Brittle Failure of Materials

When a stress is applied to any object, it deforms, i.e., changes shape and/or size. This deformation is called elastic if the object returns to its original shape after the applied stress has been removed. Deformation that is permanent is called plastic deformation.

All materials can undergo only a limited amount of elastic deformation, after which either plastic deformation sets in or the material fractures.

Materials that fracture without any plastic deformation are called brittle materials. Examples include glass and most other ceramic materials.

Ductile materials undergo plastic deformation before fracture. Examples include aluminum, copper, steel and many metals, as well as polyethylene, nylon and many other polymers.

A number of factors determine whether a material is going to behave in a ductile or brittle manner. Among these factors are

• The structure and composition of the material, i.e., what are the atoms that make up the material, how are they bonded to each other, are there impurities, etc.

• The rate at which the material is deformed

• The temperature at which the material is deformed

Generally high rates of deformation and low temperatures promote brittle fracture. Brittle failure usually occurs very rapidly and can be catastrophic. Many materials which are ductile at high temperatures become brittle when cooled below a critical temperature. This temperature is called the ductile to brittle transition temperature (DBTT) for metals and the glass transition temperature (Tg) for polymers.

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  • $\begingroup$ thanks @feetweet but that doesn't really answer my question, which could be rephrased as "Would all materials undergo catatrophic brittle failure at a low enough temperature?". That quote says "many", which doesn't address the question. $\endgroup$ – Max Williams Feb 16 '15 at 9:19
  • $\begingroup$ @MaxWilliams: We know of materials (e.g., helium) that don't even solidify at absolute zero, so no, not all matter has a brittle transition temperature. Whether all materials that solidify always have a brittle temperature may be what you mean. I bet there are some easy counterexamples, but I don't know them. $\endgroup$ – feetwet Feb 16 '15 at 16:31
  • $\begingroup$ I did mean materials which are solid at room temp actually, you're right. $\endgroup$ – Max Williams Feb 16 '15 at 16:55

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