Freezing Point vs. Amounts of Material
Most recent answer: 12/12/2015
- Anthony (age 14)
Omaha, NE, USA
For big amounts the freezing point doesn't depend on the amount.
For extremely small amounts, in principle, there's no well-defined freezing point since true phase transitions (like liquid <--> solid) only exist in the limit of infinitely large systems. In other words, if you had say 10 water molecules together, they wouldn't be clearly in an ice-like or liquid-like state.
In practice, for in-between amounts you can get something very much like a phase transition in a drop so small that the freezing temperature is slightly lowered. For example, a drop of water about 100nm across would (in equilibrium) go pretty abruptly from liquid-like to solid-like at a temperature just below 0°C. (That's around 10,000,000 molecules.) The reduction in the melting/freezing point goes as the inverse of the diameter of the drop. It's called the Gibbs-Thomson effect, as described here: https://en.wikipedia.org/wiki/Gibbs%E2%80%93Thomson_equation. By the time you get to a drop big enough to see, the effect is extremely small.
Mike W.
(published on 12/12/2015)