Which material has the lowest freezing point? (with photo)

Helium has the lowest freezing point.

The material with the lowest freezing point is helium. Under typical pressures, it does not freeze, even at temperatures close to absolute zero. The reasons are dictated by quantum mechanics: the zero-point energy of a helium system is too great to allow freezing. Zero-point energy is the minimum energy that a particle or system always has, no matter what. Helium is the only substance that does not have a freezing point at ambient pressure, regardless of temperature.

A freezing point for helium only exists under at least 25 atmospheres of pressure and a temperature of 1.15 K. These conditions were created in a laboratory through evaporative cooling. The result is a colorless, highly compressible solid that is virtually invisible. Solid helium is so hard to see that layers of Styrofoam are just used to tell where it is. The density of solid helium itself is only 66 times that of air. In comparison, water is 1000 times denser than air.

Helium was liquefied in 1908 by Dutch physicist Heike Onnes, who cooled it to 1 degree Kelvin. To his surprise, the additional cooling didn’t make him reach the freezing point. Only 18 years later, in 1926, his student Williem Keesom was able to solidify helium by cooling it in a pressure chamber. Today, liquefying helium is a vital step in extracting it from the earth and storing it.

Liquid helium is often used as a cryogenic cooling agent when liquid nitrogen is not sufficient. It must be kept under continuous high pressure and low temperature, otherwise it expands rapidly and transitions to a gas. Solid helium has no practical application outside of scientific research.

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Some of helium’s more unusual properties can be obtained at temperatures close to absolute zero. At such temperatures, helium behaves like a superfluid, meaning it flows with zero measurable viscosity. He also has a tendency to climb the walls of a container he is trapped in.

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