Download Energy

Phases of Matter and
Phase Changes
Phase

.
Depends on
strength of forces
of attraction
between particles.
Solids


Definite shape and volume.
Most dense phase


Difficult to compress.
Exception is water!.

Particles vibrate in fixed positions
Crystalline lattice structure.
Most attraction between particles.

Note:



Amorphous solids include glass,
plastic, wax, and silly putty
Liquids





Definite volume
No definite shape
Hard to compress
Particles slide past each
other
Forces of attraction
between particles still high
Gases



No definite shape or volume
Expands to fill container
Lowest density

Density depends on pressure

Little attraction between
particles

“Vapor” = a gaseous state of
something that is normally liquid

(Ex: water vapor)
Phases Applet

Short Summary video on phases: (1 min)


http://www.youtube.com/watch?v=sKvoVzukHo&safe=active
Applet: (Excellent)

https://phet.colorado.edu/en/simulation/statesof-matter

http://www.harcourtschool.com/activity/states_
of_matter/
Changes in Phase
Gas
Condensation
Vaporization
(Boiling or Evaporating)
Liquid
Solidification
Melting (fusion)
Solid
Let’s Skip a Phase

Sublimation

Directly from the solid
phase to the gas phase.

Happens with substances
with weak intermolecular
forces of attraction

They separate easily!

Ex: CO2(s) dry ice, Iodine
CO2(s) → CO2 (g)
http://www.youtube.com/watch?v=8tHOVVgGkpk
Energy

Energy = capacity to do work or produce heat.
It can be anything that causes matter to move or
change direction.

Ex: electrical, atomic, mechanical, chemical
Law of Conservation of Energy

Energy can’t be
created or
destroyed, just
transferred from
one form to another
PE vs. KE

Potential Energy
stored energy


Energy can be stored in
bonds between atoms
Kinetic Energy
energy of motion

All atoms are moving
and vibrating unless at
absolute zero
Energy and Changes to Matter

Exothermic Change:


A + B → C + D + energy
Energy is released or “ex”its
Endothermic Change: A + B + energy → C + D

Energy is absorbed or “en”ters
Energy During Phase Changes

Solid
Liquid, Liquid
Gas
Endothermic
 Energy is absorbed and overcomes attractive
forces between particles


Gas
Liquid, Liquid
Solid
Exothermic
 As particles come closer together energy is
released

http://www.kentchemistry.com/links/Matter/
HeatingCurve.htm
Heat Energy

Also called Thermal energy, it makes particles
move more as it is added

Measured in Joules or calories.
http://www.youtube.com/watch?v=f1eAOygDP5s&safe=active
Heat Flow

Heat energy
travels from an
object of higher
temp. to one of
lower temp. until
both reach the
same temp.
Temperature

Measure of the average kinetic energy
(motion) of all the particles in a sample.

Not a form of energy!!!

But if you add heat energy or take it away, it
causes particles to move faster or slower and
thus changes the temp.
Heat vs. Temperature

Teacup vs. Bathtub

Both at 25˚C

Which one contains
more heat energy?

Which one has the
greater average KE?
Label This Graph