Science Forum
15 Jul '08 17:25Solid, Liquid and Gas states are a relationship between internal energies (at the atomic and molecular scale) which is temperature, and the bonds that hold the individual molecules together (such as hydrogen bonds).
Every substance has a B.E.C., solid, liquid, gas and plasma state.
Thats right, 5 states of matter.
Not all substances have reached these states in laboratories (as far as I know) but theoretically it is possible for any type of matter to reach any of those 5 states.
15 Jul '08 18:23Originally posted by ChessJester
I thought the greater the pressure, the lower the freezing point? Hence the Vostok Lake in Antartica. I suppose that will work the other way around too.
Yup, thats right. Under correct pressures you can even make water freeze at above zero temperature.
I know about gas, solid, liquid and plasma but what is B.E.C?- 15 Jul '08 18:27
Originally posted by Wheely
I know when pressure is less the boiling point is lower - which is why tea/coffee at higher altitudes sucks.
I thought the greater the pressure, the lower the freezing point? Hence the Vostok Lake in Antartica. I suppose that will work the other way around too.
I know about gas, solid, liquid and plasma but what is B.E.C?
Is the freezing point higher then at lower pressure? right now I can't think of the logic behind it frankly. - 15 Jul '08 19:20 / 5 editsWhen the pressure increases, for most substances their melting point also increases and this may cause them to turn from a liquid to a frozen solid even without a temperature change.
But, water is one of those extremely rare exceptions to this rule! For water, when the pressure increases, its melting point decreases! The reason for this is that, unlike with virtually all other substances, as water goes from being a liquid to a frozen solid, its density decreases rather than increases! (and it therefore expands on freezing making water one of those extremely rare exceptions to that rule as well!) so therefore pressure (which tends to squash substances to make them more dense), unlike with other substances, actually opposed freezing of water rather than encouraging it.
On the other hand, water’s boiling point responds to pressure like any other substance -as pressure increases its boiling point also inceases resulting in a higher required temperature to get it to boil.
Some substances, such as CO2, don’t have a liquid phase at one atmospheric pressure but do have a liquid phase at much higher pressures. No substance has a stable liquid phase at zero pressure. For example, it is impossible to have liquid water in the vacuum of outer space and liquid water, depending on its temperature, either instantly freezes solid or boils into gas or does a combination of both when exposed to a total vacuum. - 15 Jul '08 19:35
Originally posted by Wheely
Its called Bose-Einstein Condensate.
I thought the greater the pressure, the lower the freezing point? Hence the Vostok Lake in Antartica. I suppose that will work the other way around too.
I know about gas, solid, liquid and plasma but what is B.E.C?
http://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate
http://www.colorado.edu/physics/2000/bec/ - 15 Jul '08 20:10
Originally posted by Andrew Hamilton
Cool, thanks for that!
When the pressure increases, for most substances their melting point also increases and this may cause them to turn from a liquid to a frozen solid even without a temperature change.
But, water is one of those extremely rare exceptions to this rule! For water, when the pressure increases, its melting point decreases! The reason for this is that, ...[text shortened]... ly freezes solid or boils into gas or does a combination of both when exposed to a total vacuum. 
15 Jul '08 20:13Originally posted by PsychoPawn
More pressure helps squeeze molecules into liquid from gas, or solid from liquid.
I know when pressure is less the boiling point is lower - which is why tea/coffee at higher altitudes sucks.
Is the freezing point higher then at lower pressure? right now I can't think of the logic behind it frankly.- 15 Jul '08 23:10 / 1 editThere are only a few elements, 100 or so. This means there are not that many possible simple combinations that gives the specs of a water molecule, the angle of 105 degrees between the O and the H for instance. That is set by the energy levels of those two gasses. There just are not that many possible combinations of two elements. 100 squared, or about 10,000 total, so next up the ladder is helium and lithium, you get much higher than that and the individual atoms start getting internally very complex, so stuff like H2S is not even liquid at room temp. It would be hard to make somthing like HeO, helium oxide, for instance. Lithium oxide for sure but that would never be a liquid under normal room temps.
It just goes to show you how special water is and how absolutely vital it is for our kind of life. If water did not decrease it's density when freezing, life would not be possible, our kind of life anyway, ice would sink and the whole thing would freeze solid. As it is, ice floats which makes an insulating layer that protects the underlying water from freezing unless temps got REALLY cold. That is helped out by the fact that under the oceans, heat rises up from the belly of the planet due to thermonuclear reactions deep underground and friction from sliding continents and such.
