The Nobel Prize in Physics 1996

	Phases and phase transitions
	Depending on pressure and temperature, a substance can exist in three phases – as gas, liquid or solid. Water for example exists as steam, water or ice. The transition between phases may be noticed as abrupt changes in pressure and temperature. At normal pressures both ⁴He and ³He refuse to freeze no matter how low the temperature. The explanation is that no atoms can be completely at rest (zero point motion) and that the attractive force between helium atoms is too weak to make them come to rest. However, if the pressure is increased to about 3 MPa (30 atmospheres) both fluids become solids at very low temperatures.

Contents:
Introduction » Significant kinks » Helium » Colder than cold » Superfluidity » Phases and phase transition » Statistical laws explain differences » How ³He becomes superfluid » Whirlpools » Further reading »
Based on materials from the 1996 Nobel Poster for Physics. Credits and references for the poster »

Phases and phase transitions