If absolute zero is as cold as matter can be, is there a limit to how hot matter can be?

Question

If molecular motion stops at -273 C, then is there an opposite end to that spectrum? A student posed this question to me and I had no response.
Simple terms please, been awhile since I've reviewed my advanced thermodynamics :)

Answer 1

Yes. Once a substance absorbs so much energy that the nuclear bonds are broken in the nucleus, it disintegrates and the substance is no more. When that amount of energy level is reached that is the highest "Temperature". it is usually referred to as plasma then.

Answer 2

There are only theoretical limits to how hot a substance can get. Consider this: water melts easily. Steel is difficult to melt, but it can be done. Can you melt a brick? In theory, yes, but what would you hold it in that would not melt at the same time?

We can only make something as hot as the container we put it in can withstand.

If a substance is heated beyond the gaseous phase, its electrons will disociate, forming a plasma. At this point, the radiant energy (mostly light and nuetrinos, and some other radiation as well) of the substance starts to become an issue. Inputting more energy (say, by way of remot microwave lasers) will result in more radiation, which acts to disipate heat. At some point, one of two things will happen:

The substance will gain enough energy to undergo fussion; it will become immensely more hot until it burns itself out. Additional heating may initiate another fussion process, but at some point, the material is too dense and then...

The radiant energy of the substance will exactly balance out the input of energy, and it cannot increase in temperature.

Both of these cases are wild extremes that could never be realized in experiment, though, so the entire endevour is purely mental, but a good one none-the-less! Keep an eye on that student of yours!

Answer 3

Well, of course at high temperatures atoms basically fall to bit, so the idea of temperature becomes harder to pin down. However, you can still define a thermodynamic temperature.

The ultimate source of a limit on high temperature is the fact that nothing can exceed the speed of light. So when a material is hot enough that some of its particles are near the speed of light, it will no longer get any hotter (the temperature is related to the spread of particle velocities).

Answer 4

I don't know of any theoretical limit, but I can think of two practical ones: 1) There's a finite amount of energy in the universe, so if you put all of it into one particle - that's as hot as it gets. 2) At some point, the quarks that make up protons and neutrons might themselves break up into massless particles by E=mc^2 and then they would no longer be "matter." #2 is a guess though. Ask a nuclear physicist.

Answer 5

Everything burns, everything freezes. Both are impossible to reach. Absolute zero has never been documented. It is a theoretical minimum. If the theoretical minimum is the cessation of movement, then the theoretical maximum would be infinite movement. So we would have to find the temperature at which the densest element begins to burn in such a way that no atoms are left (due to their infinite movement). Technically, it would have to be so hot as to cause all the atoms of our test subject to go nuclear and destroy themselves from their "infinite motion". This heat would be as impossible to reach as the impossible cold of Absolute Zero.

Answer 6

Heat is a measure of the average kinetic energy of molecules. Since the total energy in the universe is a constant (you can change the form of energy, but you cannot create or destroy it), then the theoretical limit (I suppose) would be the temperature at the big bang in which all the energy was kinetic. According to Wikipedia, this temperature was 1.417 × 1032 °C

Answer 7

Practically speaking, a maximum temperature exists for different matter. High temperatures would cause atoms to split into their respective sub-atomic particles. You would have to realize that the increase in kinetic energy, due to the increase in temperature, results in combustion as well. Some claim it leads to fusion, the process whic occurs in stars.

Since temeprature is proportional to kinetic energy, and kinetic energy is proportional to velocity, we return to basic physics laws to find the limit. The laws of physics hold true as long as velocity is less than or equal to that of the speed of light.

The theory of relativety states that at very high velocities, the particle's mass tends to increase. Mass is defined as something that tends to resist acceleration. Thus, the increasingly larger mass would require increasingly tremendous amounts of energy to raise the velocity ever so slightly. Therefore, the limit to maximum temperature is where energy meets the highest velocity possible, the speed of light. I'm not sure what that is, but I can guarantee you that we cannot achieve such temperatures to attain lightspeed. We'll stick to conventional electron accelerators to achieve 0.997C using magnetism.

Answer 8

If you're using the first part of your question as a guide on how to answer the second part, then the answer is no. You can theoretically keep adding energy to the matter, even if it's in a plasma state.

Answer 9

Can you imagine the concept of zero? That's absolute zero.
Can you estimate the value of infinity? Of course not, there is no upper limit because infinity is not countable.
It's a matter of logic, not thermodynamics.

Answer 10

There sort of has to be, because eventually the molecular motion would reach light speed, wouldn't it? At that point, it seems to me it could get no hotter because the molecules can't move faster.