My freezer is set at -21°C (-6°F) and tubs of ice cream come out hard as a rock and are near impossible to scoop. But if I set it a few degrees warmer, yet still way below the freezing point of water, I can scoop it easily. So, is there such a thing as both frozen and *really* frozen? Conversely, a boiling point is a boiling point, I believe. Heating water to a temp above 100°C gets you the same steam that you got at 100, just faster. Right?
In: 102
In the boiling situation, for example, you physically cannot heat liquid water above 100 C at 1 atm of pressure because the liquid transforms to vapour.
On the opposite surface of where the heat is being applied, i.e., where the bubbles are forming, the vapour bubbles can continue to heat above 100 C and form a kind of ‘insulation’, so that’s why the temperature at that surface might be higher than the bulk liquid.
The temperature difference between the heat source and the thing you are heating controls how fast the energy is transferred. So if the heat source is 110 C, it will take a very long time to start boiling, and if it’s 800 C gas flame then it will go faster.
Related to what I said above, if the heat source is extremely hot, you will form a layer of insulating bubbles and the speed after some point will slow down again. This is called film boiling, and the good efficient kind of boiling is called nucleate boiling.
For the ice cream situation, ice cream is complicated. You will probably find that it scoops easily when it’s new, but then gets harder every time you remove it. The post by /u/honey_102b explains in more detail.
Freezing just means “has transformed from a liquid to a solid”, so a ‘really frozen’ doesn’t exist.
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