Which temperature scale has 0 degrees as its ice point?

The Celsius scale is defined such that 0 degrees represents the freezing point of water (the ice point). This choice is significant because it has been established based on the physical properties of water, one of the most common substances studied in science.

In the Celsius scale, water freezes at 0 degrees and boils at 100 degrees at standard atmospheric pressure, providing a straightforward and intuitive framework for understanding temperature changes during physical processes involving water.

While the Fahrenheit scale has its own freezing point set at 32 degrees and is commonly used in the United States, and the Kelvin scale, which is absolute and starts at absolute zero (0 K), uses a different zero point based on thermodynamic principles, the Celsius scale’s use of 0 degrees directly correlates to a readily observable and significant natural phenomenon: the phase transition of water from liquid to solid.

The Rankine scale, similar to Kelvin but aligned with the Fahrenheit scale, also does not use 0 degrees as the ice point, further differentiating it from the Celsius scale. Thus, the Celsius scale's defining characteristic includes its clear connection between temperature readings and the physical state of water, validating why 0 degrees is recognized as the ice point in this context.