Question

What do the sections between the lines on the phase diagram below represent?

Answer 1

The way I interpret this graph is the range of factors/conditions that influence states of matter of water to change.

The lines simply represent the border between each state.

For example, for water to be in a solid state, the temperature can vary from `~10^oC` to `0.01^oC`, as long as the (air) pressure is somewhere between `0` `"atm"` to `~~2`.

The independent variable corresponds to the dependent variable.

Hope this helps :)