#freezing point

Prior to 1743, the Celsius scale values were reversed (i.e. the boiling point was 0 degrees and the freezing point was 100 degrees). The 1743 scale reversal was proposed by Jean-Pierre Christin. – WTF Fun Facts

Vouching for Vonnegut: Engineers study polymer that freezes at room temperature

In Kurt Vonnegut's sci-fi classic Cat's Cradle, ice-nine is a substance capable of raising water's melting point from 32 to 114.4 degrees Fahrenheit. Once in contact with water, it spreads instantly and indefinitely, leaving frozen oceans and chilling consequences in its wake. Luckily, as Vonnegut explains in the epigraph, 'Nothing in this book is true.' When he wrote the novel in 1963, he may have been right.

Researchers at the University of Pittsburgh have discovered the fantastic behavior of a liquid polymer capable of freezing water at room temperature. Beyond giving credence to Vonnegut's prophetic imagination, the resulting mixture seemingly defies the second law of thermodynamics, which states that within an isolated system, entropy always increases.

"When you mix two pure components together, the entropy (or the degree of disorder), always increases," explains John Keith, assistant professor of chemical engineering and Richard King Mellon Faculty Fellow in Energy at Pitt's Swanson School of Engineering. "That disorder almost always causes mixtures to have a lower freezing point than either of the components individually, not higher."

The mixture of salt and water, for example, freezes at lower temperatures than either salt or water individually. This quality makes salt well-suited for melting ice on roads and sidewalks in the winter. However, when a particular polymer—known as polyoxacyclobutane (POCB)— is mixed with water, it raises the mixture's freezing point from 32 degrees Fahrenheit to about 100 degrees Fahrenheit. The researchers published their findings in the American Chemical Society (ACS) journal Macromolecules.