Question

Which phase(s) is/are present at the following point? Preopure Tenpersture What does the point D correspond to? Describe what happens when you increase the temperature at constant pressure, starting at point A? Describe what happens when you decrease the pressure at constant temperature, starting at point H?

Answer 1

Look at the pic above to see which phase exists in which portion.

Point A: only solid phase exists

Point B: all three phases, i.e. solid, liquid, vapor exist. This is also called triple point

Point C: only vapor phase exists

Point E: both solid and liquid phase exist

Point F: both vapor and liquid exists

Point H: only liquid phase exists

Point D is the critical point. Above this temperature, it is not possible to liquefy the gas by applying any amount of pressure

Starting at point A, when temperature is increased at constant pressure, that is, when we move horizontally along the graph from point A, we see that first solid will get heated up and then it will convert to liquid, Then liquid will get heated up and it will become vapor.

Starting at point H, when pressure is decreased at constant temperature, that is, when we move vertically down the graph from point H, we see that liquid will cool and then get converted to solid,