The document discusses the different phases of matter (solid, liquid, gas) and the phase changes between them. When energy is added to a solid, its bonds break and it melts into a liquid where particles can move freely. Adding more energy turns the liquid into a gas where particles move randomly. The phase changes - melting/freezing, vaporization/condensation, sublimation/deposition - describe the changes in particle arrangement that occur when energy is added or removed. Phase changes are classified as endothermic, where energy is absorbed during the change, or exothermic, where energy is released.

1. Phase Changes

2. Do Now:
What are the names for the phases that
matter goes through when changing
from solid to liquid to gas, and then
back again?

3. States of Matter - Review
By adding energy, usually in the form
of heat, the bonds that hold a solid
together can slowly break apart. The
object goes from one state, or
phase, to another.
These changes
are called PHASE
CHANGES.

4. Solids
A solid is an ordered
arrangement of
particles that have
very little movement.
The particles vibrate
back and forth but
remain closely
attracted to each
other.

5. Liquids
A liquid is an
arrangement of less
ordered particles
that have gained
energy and can move
about more freely.
Their attraction is
less than a solid.

6. Compare the two states:

7. Gases
By adding energy, solids can change from
an ordered arrangement to a less ordered
arrangement (liquid), and finally to a very
random arrangement of the particles (the
gas phase).

8. Each phase change has a specific name,
based on what is happening to the
particles of matter.

9. Melting and Freezing
The solid, ordered
molecules gain energy,
collide more, and
become less ordered.
The less ordered liquid
molecules loose energy,
slow down, and become
more ordered.

10. Condensation and Vaporization
The less ordered gas
molecules loose energy,
slow down, and become
more ordered.
The more ordered liquid
molecules gain energy, speed
up, and become less ordered.
Evaporation only occurs at
the surface of a liquid.
Boiling occurs throughout the
liquid.

11. Sublimation and Deposition
The more ordered solid
gains energy, the
molecules speed up and
become less ordered gas.
Liquid phase is bypassed.
The less ordered
gas looses energy,
molecules slow
down, and become a
solid (frost). Liquid
phase is bypassed

12. Phase changes are classified as
one of two types:
1. ENDOTHERMIC – The object absorbs
energy from the surroundings. Think
of ENDO as “entering”: energy comes
into the object. What is happening to
the particles?
2. EXOTHERMIC – The object releases
energy to the surroundings. Think of
EXO as “exiting”: energy goes out of
the object. What is happening to the
particles now?

13. Now we can complete the
remaining two columns of
the study guide.