FYI - Helium

 

Helium only becomes liquid at absolute zero, unlike other elements. Helium behaves differently from many other elements when it comes to its liquid state primarily due to its unique physical properties and the behavior of its atoms at very low temperatures. Here’s a detailed explanation of why helium becomes a liquid at a temperature very close to absolute zero:

Quantum Mechanical Explanation

1. Bose-Einstein Condensation (BEC):

   • At extremely low temperatures, atoms behave according to quantum mechanical principles. Helium-4 (the most common isotope of helium) exhibits a phenomenon known as Bose-Einstein condensation.
   • When helium-4 is cooled to near absolute zero (approximately 2.17 Kelvin or -270.98 degrees Celsius), the atoms start to condense into the lowest quantum state. This results in the formation of a quantum fluid, known as a superfluid.

2. Superfluidity:

   • Below the critical temperature of 2.17 K, liquid helium-4 transitions into a state where it flows without viscosity, known as a superfluid. This superfluid state arises because a significant fraction of helium-4 atoms occupy the same quantum state due to Bose-Einstein condensation.
   • The superfluidity of helium-4 is a quantum mechanical phenomenon where the atoms move collectively and can flow through extremely small spaces without friction, even crawling up the walls of containers (a phenomenon known as superflow).

Helium-3 and Quantum Statistics

1. Helium-3 Behaviour:
   • Helium-3, another isotope of helium, does not exhibit Bose-Einstein condensation at the same temperatures as helium-4 due to its fermionic nature (having half-integer spin and obeying Fermi-Dirac statistics).
   • Instead, helium-3 forms a liquid at temperatures around 0.0025 K, which is still very low but significantly higher than the critical temperature of helium-4.

Classical vs. Quantum Behaviour

1. Classical Gases vs. Helium:
   • Classical gases (like most elements) condense into liquids when cooled sufficiently because the kinetic energy of their atoms decreases to the point where attractive intermolecular forces (van der Waals forces) can hold them together in a liquid phase.
   • Helium, particularly helium-4, behaves differently because its atoms are bosons (integer spin) and can undergo Bose-Einstein condensation at much lower temperatures, near absolute zero. This is a quantum effect that does not occur with other elements under normal conditions.

In summary, helium-4 becomes a liquid at temperatures very close to absolute zero (2.17 K) due to Bose-Einstein condensation, a quantum mechanical phenomenon where a significant fraction of atoms occupy the lowest quantum state. This results in the formation of a superfluid, which flows without viscosity. Helium-3, another isotope of helium, behaves differently due to its fermionic nature and forms a liquid at slightly higher temperatures. The unique behaviour of helium at low temperatures is a direct consequence of quantum mechanics and the specific quantum statistics (Bose or Fermi) governing its atoms.

Source: Some or all of the content was generated using an AI language model