“Professor Holmes, how would you visually present a phase diagram in a
simpler way?” Alice asked.
“That is a very good question. In fact, I was just about to explain that,”
the professor replied.
“The phase diagram can be likened to a map (Fig. 2.3). Instead of going
towards the east or the west, or from north to south, you go from low to high
pressures or from low to high temperatures.”
“You can either go in the east-west direction or in the north-south direction,”
he went on, pointing to a map of the United States. “We say that we
have two degrees of freedom to walk on the map.”
Someone interrupted him. “We can also go up or down in the real world,
Professor.”
“That is a very good comment,” said the professor. “Indeed, in the real
world, we can also go up and down when we descend or ascend a hill or
go to the upper or the lower floors of a building. In the real world, we can
move in three dimensions; we have three degrees of freedom. However, on this
particular map, we shall restrict our movements to a two-dimensional world,