Re: Do all liquids freeze?

Dear Max,

Both pressure and temperature influence the state of a substance (i.e. solid, liquid, gas). You are familiar with the effects of temperature: at low temperatures, materials usually solidify and at higher temperatures, they usually melt into liquids then boil into gases. (Note that sometimes materials can go straight from solid to gas, a process called sublimation. Dry ice, which is frozen CO2, can do this.) You are probably not familiar with the effect of pressure, since in a normal environment it does not change. At high pressures, materials are squeezed into solids and at lower pressures materials exist as liquids and gases.

Furthermore, there is a lower limit on temperature--materials cannot be cooled forever. The temperature limit is called absolute zero, and is equal to about -460 F. Near absolute zero, at normal pressure, helium is a liquid and not a solid. In fact, helium is the only known substance that does not solidify near absolute zero at normal pressures. However, if the pressure is increased (to around 30 times normal), helium will become solid.

So, to conclude, everything except helium will freeze if cooled enough at normal pressure and even helium will become solid when compressed.

Your MAD Scientist,
Raymond Cheong

References

http://www.treasu re-troves.com/physics/Helium.html