Unit 1: Intro to
Chemistry
Phase Diagrams
After today you will be able to…
• Draw a phase diagram and label each
state of matter, changes of state, and
the triple point
• Identify at what temperature or
pressure a substance will change state
• Identify which state is the most/least
dense form and n.B.P and n.F.P.
A phase diagram shows the
conditions of temperature and
pressure that are necessary for
a substance to exist as a solid,
liquid, or gas.
Phase Diagram for Water
Pressure
(kPa)
LIQUID
101.3
Triple
Point
GAS
SOLID
n.M.P.= 0°C
n.B.P.=100°C
Temperature (°C)
Triple point: The conditions of
temperature and pressure at
which all three states of matter
are in equilibrium with each other
(S, L, G, exist simultaneously).
The Triple
Point of
Water:
Two Types of Phase Diagrams:
1. Liquid state is more dense than
the solid state (Example: water –
ice floats!)
2. Solid state is more dense than the
liquid state (Example: most
substances)
• If the solid/liquid line slants to the left, the
liquid state is more dense than the solid state
(liquid region is larger).
LIQUID
SOLID
GAS
• If the solid/liquid line slants to the right, the
solid state is denser than the liquid state
(solid region is larger).
LIQUID
SOLID
GAS