This document discusses the properties of solids, liquids, and gases. It explains that in solids, particles are fixed in place with strong intermolecular forces, while in liquids they are closer together but with more motion. In gases, particles are far apart with minimal intermolecular forces and take the shape and volume of their container. It also describes evaporation as a process where molecules gain energy to break intermolecular bonds and become a gas, and condensation as the opposite where gases release energy and form bonds to become liquids. Dynamic equilibrium is reached when the rates of evaporation and condensation are equal in a closed system.

1. Solid, Liquid, Gas
(a) Particles in solid (b) Particles in liquid (c) Particles in gas

2. Solid
H2O(s) Ice
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 31

3. Ice
H2O(s) Ice
Photograph of ice model Photograph of snowflakes
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

4. Liquid
H2O(l) Water
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 31
In a liquid
• molecules are in
constant motion
• there are appreciable
intermolecular forces
• molecules are close
together
• Liquids are almost
incompressible
• Liquids do not fill the
container

5. Gas
H2O(g) Steam
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 31

6. Liquids
The two key properties we need to describe are
EVAPORATION and its opposite CONDENSATION
add energy and break intermolecular bonds
EVAPORATION
release energy and form intermolecular bonds
CONDENSATION

7. States of Matter

8. Gas, Liquid, and Solid
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 441
Gas Liquid Solid

9. States of Matter
Solid Liquid Gas
Holds Shape
Fixed Volume
Shape of Container
Free Surface
Fixed Volume
Shape of Container
Volume of Container
heat heat

10. Some Properties of Solids, Liquids, and Gases
Property Solid Liquid Gas
Shape Has definite shape Takes the shape of Takes the shape
the container of its container
Volume Has a definite volume Has a definite volume Fills the volume of
the container
Arrangement of Fixed, very close Random, close Random, far apart
Particles
Interactions between Very strong Strong Essentially none
particles

11. • To evaporate, molecules must have
sufficient energy to break IM forces.
• Molecules at the surface break away
and become gas.
• Only those with enough KE escape.
• Breaking IM forces requires energy. The
process of evaporation is endothermic.
• Evaporation is a cooling process.
• It requires heat.
Evaporation

12. Change from gas to liquid
Achieves a dynamic equilibrium with
vaporization in a closed system.
What is a closed system?
A closed system means
matter can’t go in or out.
(put a cork in it)
What the heck is a
“dynamic equilibrium?”
Condensation

13. When first sealed, the molecules
gradually escape the surface of the
liquid.
As the molecules build up above the
liquid - some condense back to a
liquid.
The rate at which the molecules
evaporate and condense are equal.
Dynamic Equilibrium

14. As time goes by the rate of vaporization
remains constant but the rate of
condensation increases because there
are more molecules to condense.
Equilibrium is reached when:
Rate of Vaporization = Rate of Condensation
Molecules are constantly changing phase “dynamic”
The total amount of liquid and vapor remains constant
“equilibrium”
Dynamic Equilibrium

15. • Vaporization is an endothermic process - it
requires heat.
• Energy is required to overcome intermolecular
forces
• Responsible for cool earth
• Why we sweat
Vaporization

16. Energy Changes Accompanying Phase Changes
Solid
Liquid
Gas
Melting Freezing
Deposition
Condensation
Vaporization
Sublimation
Energy
of
system
Brown, LeMay, Bursten, Chemistry 2000, page 405