Chapter_11.1
Chapter 11:
States of
Matter and
Intermolecul ar Forces
Section 11.1: pg. 376-384;
S.O.L. Ch 3d, 5 d,f
States of Matter
The states of matter are solid, liquid, gas and sometimes plasma (which is not a naturally occurring state)
It’s just a phase!
A phase is a uniform collection of particles.
Some things can exist in two phases
(milkshakes, slushies, etc.)
Dynamic equilibrium is a state of a compound where the particles move between 2 different states.
Phase Diagrams
A phase diagram shows the state of a compound with temperature and pressure.
The diagram shows the state of matter at a given temperature and pressure.
The Phase Diagram
Boiling and Melting
When you consider standard atmospheric pressure
(1 atm), the point where the phase lines intersect are the melting and boiling points, respectively.
Melting point: the temperature and pressure where a solid becomes a liquid. (solid and liquid are in equilibrium)
Boiling point: the temperature and pressure where a liquid becomes a gas. (liquid and gas are in equilibrium)
Temperature or Pressure
Change
You can add energy in the form of heat to raise the average kinetic energy of a substance, OR you can increase the pressure.
Definitions
Triple point: the temperature and pressure at which all three states of matter exist at equilibrium.
Critical point: the temperature and pressure where gas and liquid become identical.
Above this point the substance is said to be a supercritical fluid
Vapor Pressure
Vapor pressure is the pressure produced by a liquid or a solid when it is in dynamic equilibrium with its gas phase and is measured in mmHg or kPa.
As temperature increases, vapor pressure increases and exerts pressure on the walls of the container.
Drawing a phase diagram
To plot the phase diagram, you will need the
Triple point
Critical point
Vapor Pressure at 1 atm
Draw this
The triple point of SO
2 is -73C and 0.17 kPa. The critical point is 158C and 7,870 kPa. The bp is -10C. The solid form is more dense than the liquid form.
Phase Diagram
7870 kPa
101.3 kPa
0.17 kPa
-73C -10C 158C
Answer these
What state is SO
2 in at 200kPa and -100C?
What state at 1 kPa and 80C?
If you increase temp at 101.3 kPa from -
20C to 20C, what happens?
If you increase pressure at -11C from 150 kPa to 300 kPa, what happens?
Forces of Physical Properties
Cohesion is an attraction for particles that a liquid has.
Adhesion is an attractive force for particles of solid surfaces
Capillary action is the motion of a liquid up a small surface and is accomplished by adhesion of liquid molecules to the surface of the glass as well as cohesion between the liquid molecules.
Surface Tension
Surface tension is the force that acts of the surface of a liquid and tends to minimize the area of the surface. Why?
1 st of all, cohesive forces bring the molecules of a liquid together so that they stay in contact;
2 nd , under the surface of the liquid, these cohesive forces are pulling equally in all directions;
3 rd , only on the surface, the molecules are being pulled sideways and downward creating
surface tension.
The Energy of Tension
It takes energy to increase the surface area of a liquid because this energy must oppose the net forces pulling the molecules; conversely, a liquid decrease energy as the surface area decreases.
This tendency toward decreasing the surface area is called surface tension.
A high surface tension means that a lot of energy is needed to break the surface.
Application of Surface Tension
When you add the detergent to a load of laundry, the soap decreases the surface tension of the stain on your clothing by disrupting hydrogen bonds; therefore the dirt can be carried away by the water!!!
Although, it also takes effort to load the washing machine!
How do we have states?
The determining factor as to whether a molecular substance is a solid, liquid or gas at room temperature is its intermolecular forces.
Intermolecular forces - forces of attraction that exist between molecules. (More to come!)
Gases are Special
Gases do not have the same type of intermolecular forces, because they are farther apart and the attractive forces are minimized. That is why a gas will fill the space available.
Condensed States of Matter
Liquids and Solids
Kinetic-molecular theory for gases establishes that gas particles have significant kinetic energy and little attractive forces between them and therefore act independently of one another.
According to kinetic-molecular theory, the state of a substance at room temperature depends on the strength of attraction between the particles.
Changes in State
A phase change is the conversion of a substance from one of the three physical states of matter to another.
A phase change always involves a change in energy .
Name that State Change
condensation - release energy to convert gas to liquid
deposition - release energy to covert gas to solid
freezing - release energy to convert liquid to solid
melting - absorb energy to convert solid to liquid
sublimation - absorb energy to convert solid to gas
vaporization - absorb energy to convert liquid to gas
The Water Cycle
Endothermic
Gas
Exothermic
Liquid
Solid
Homework
Read Chapter 11.1
Answer Section Review Questions
