Originally posted by: bobdole369
It's been my experience that Diet Coke somehow freezes at above 32F. also if you take a coke and a diet coke together in the freeze - the diet coke will be undrinkably frozen in 15 minutes, while the coke, merely cold. Takes about an hour for undiet coke to freeze.
Dunno why that is.
Exactly right (well, almost - Diet does NOT freeze at higher than 32 F), and here's why (from a Chemist).
When you dissolve something (the solute) in a solvent (in Cokes, that's the water), the freezing point of the solution is LOWERED (we use the term"depressed!") compared to the pure solvent. The amount it is lowered is proportional to the concentration of solute in the solvent. The mathematical model looks like ?T = K m, where ?T is the "freezing point depression", K is a constant that is a property of the
solvent, and m is the
solute concentration in a unit called molality.
So, comparing regular and diet Coke, the regular has a lot of sugar in it, whereas the diet has no sugar and only a small amount of a synthetic sweetener that is so strong it delivers the taste at very low concentrations. Hence, the "m" factor for regular is much bigger than for Diet Coke. The other factor, K, depends solely on the water solvent, so changing which solute is involved (sugar or synthetic sweetener) does not affect the value of "K". The result is that the ?T is much larger for regular Coke that for Diet Coke, and so it won't freeze until the regular type is cooled down to a colder temperature. In fact, the ?T value for Diet Coke, with only a very small value for "m", is so small that the diet Coke will freeze almost at the same temperature as plain water, 32 F.
