What's this about water at 100 C? Wouldn't it have completely vaporized in the process? I haven't been able to get water out of my kettle, or in a pot on the stove, to register beyond 95 or so.
gus_massa•8mo ago
A long time ago we made a few experiments about water cooling inside a glass of plastic. It goes from 100°C to 60°C very fast. It's very difficult to get a value over 95°C.
The simple model predicts that temp(t)-temp_environment is an exponential and then if you graph log(temp(t)-temp_environment) should be a line. But if you run the experiment it's curved a goes down very fast until 60°C and then it's a line as the model predict.
gus_massa•8mo ago
I forgot about the 100°C.
If you put the thermometer inside the kettle inside the water, it should be at exactly 100°C, assuming 1atm of pressure, pure water and and a few more technical details. Also, is you put the thermometer inside the kettle inside the vapor it should be at exactly 100°C, assuming 1atm of pressure, pure water and and a few more technical details.
All those 100°C assume equilibrium or near equilibrium, so the very hot bottom of the kettle, the cold top, and the flowing stream may cause some problems.
For some reason it's easier to visualize with water+ice instead of water+vapor, perhaps because it's easier to play with the mix.
If you put water in the freezer, the temperature goes down to exactly 0°C, then it starts to freeze and both the water and the ice are at 0°C until you have a solid block of ice at 0°C and then, only then, the temperature continue to go down.
The same happens in the oposite direction, from ice to liquid water. And the same happens with ice to vapor transition.
zahlman•8mo ago
gus_massa•8mo ago
The simple model predicts that temp(t)-temp_environment is an exponential and then if you graph log(temp(t)-temp_environment) should be a line. But if you run the experiment it's curved a goes down very fast until 60°C and then it's a line as the model predict.
gus_massa•8mo ago
If you put the thermometer inside the kettle inside the water, it should be at exactly 100°C, assuming 1atm of pressure, pure water and and a few more technical details. Also, is you put the thermometer inside the kettle inside the vapor it should be at exactly 100°C, assuming 1atm of pressure, pure water and and a few more technical details.
All those 100°C assume equilibrium or near equilibrium, so the very hot bottom of the kettle, the cold top, and the flowing stream may cause some problems.
For some reason it's easier to visualize with water+ice instead of water+vapor, perhaps because it's easier to play with the mix.
If you put water in the freezer, the temperature goes down to exactly 0°C, then it starts to freeze and both the water and the ice are at 0°C until you have a solid block of ice at 0°C and then, only then, the temperature continue to go down.
The same happens in the oposite direction, from ice to liquid water. And the same happens with ice to vapor transition.
brudgers•8mo ago
Boiling point depends on air pressure.
[/Pedantic]
Taking "100C" literally is maybe similar.