“In Fig. 2.6, we show
the three important points
in the phase diagram of water:
the triple point (TP), the normal
boiling point (NBP), and
the critical point (CP). We
can reach the critical point by
moving along the liquid-vapor
equilibrium line — the blue
line in the diagram. As we
increase the temperature, the
pressure also increases. Recall
that along this line the vapor
and the liquid co-exist.”
“However, as we move up the line, the two phases have different densities.
But at the critical point (CP) the two phases become identical and at that point
the blue curve comes to an end. Beyond that point there exists only one phase,
and no longer two phases at equilibrium.”
“The critical point is a very interesting point for any liquid, not only for
water. However, it is at quite high temperature and pressure — beyond the
range of T and P at which life can exist. Note also that there exists no analog
of the CP along the solid-liquid phase.”
With this we end today’s lecture. I urge all of you to read the handouts which
I have given you earlier, and if there are things that you do not understand, we
can discuss them when we meet again.
Alice felt a little better today although she was still not certain if she could
grasp the big picture. She wanted to fully understand and not grope in the
dark. So she decided to approach the professor and consult him. Immediately
after the lecture she went to his office.
“I will be with you shortly as I have to talk to the convention coordinator
about the arrangements for our guest speakers.” He left immediately, not even
allowing Alice to acknowledge what he had said.