Hi Jed,
What you wrote is true when there is liquid water and steam together in
a container - the combination cannot be heated to a temperature higher
than 100 deg C without raising the pressure. However once all the
liquid has turned to gas there is no longer any limit to what
temperature it can be raised to until the molecules dissociate into
their component elements.
This is analogous to the case of ice and water together in a container.
You cannot raise the temperature of the water above 0 deg C until all
the ice has melted. Once the ice is melted, then the temperature of the
water can easily be raised - until it boils for instance.
The reason for both of these is the same - the latent heat of the phase
change. In the first case it is the latent heat of vaporization, and in
the second it is the latent heat of fusion. While there is a mixture of
water in two different phases, then all the energy is absorbed by the
water changing phase until it is complete, after that the energy added
goes directly into temperature rise instead of driving the phase
change. Much the same thing happens as you extract energy to lower the
temperature.
On 2/10/2011 10:43 AM, Jed Rothwell wrote:
Nope. It is 100 deg C. This is well established. The only way you can
raise the temperature is to pressurize it. It does not matter what the
temperature of kettle surface is.
