CHAPTER 2
SOLIDS, LIQUIDS, & GASES
I. States of Matter matter can exist in the universe in 4
states or phases
- solid, liquid, gas, plasma
 A.
Solids - have definite volume &
definite shape
1. Particles in a solid
- are packed tightly together
- stay in fixed positions - shape
- are hard to separate
In a solid,
the
molecules
are tightly
bound
together  which
holds a
shape.


(Molecular Motion)
They
vibrate in
place
2. Types of Solids

a. Crystalline solids - particles form
regular repeating patterns
Iron pyrite
- ex.s sugar, salt, sand,
snow
 Melting
point - the
distinct
temp. at
which a
crystalline
solid melts.
The crystal structure of snow
The molecular structure of salt & a
microphotograph of salt crystals.
b. Amorphous Solids
 Particles
are not arranged in
regular patterns.
 Do not have distinct melting
point temperatures (just get
softer & softer)
 behave like slow moving,
super-cooled liquids
- Can lose their shape under certain
conditions
Ex.s - plastics, rubber, glass, wax,
tar
Wax - an
amorphous
solid
B. Liquids
 No
definite shape
but a definite
volume - takes on
the shape of its
container.
 Particles not held as
closely together free to move - flow.
(Molecular Motion)
- 100 mL of water = 100 mL in any
shaped container. (Definite volume)
 Liquids
do not easily compress
or expand.
 Viscosity
- (a property of
liquids) is the resistance of a
liquid to flow

- honey has a high viscosity
compared to water
Is lava liquid? Is it viscous?
C. Gases
 Have
no definite shape or
volume - volume can change.
 Will
fill any available space - a
small amount of gas can fill a
large volume.
 Will
expand without limit.
-Gases can be
compressed.
A larger
amount forced
into a smaller
space. (A
change of
volume)
The tanks worn by this diver contain
several hours of air. How does this
work?
(Molecular Motion)
Molecules of
a gas are free
to move. They
move very
rapidly and are
in constant
motion.
This is the Eagle Nebula. Its gas &
dust are expanding in space.
What would happen if this balloon had
a hole in it? What “limits” the gas?
D. Plasma
 1.
Plasma is - a super-heated,
electrically charged gas.
 Plasma
 Plasma
is rare on earth.
is extremely energetic
& dangerous.
Examples of plasma
- the sun
Light bulbs
&
Neon lights
Lightning
Remember - particles of matter
always move. (Molecular Motion)
 Solids
- particles vibrate in
place, tightly bound together
 Liquids - particles are freer,
move faster - flow
 Gases - particles even more
free, rapid movement
 Plasma - very rapid
movement, lots of energy
Temperature affects particle movement.
Heat - move faster. Cold - move slower.
Absolute
zero the temp. at
which all
molecular
motion
ceases.
 - 273o C
 0o Kelvin
 - 459o F

This is dry
ice (CO2).
What
happens to it
as the
temperature
rises?
What are its
molecules
doing?
This is water
ice (H2O).
What
happens to it
as the
temperature
rises?
What are its
molecules
doing?
II. Gas Behavior
 A.
Measuring Gases
 1. - volume can change - gas will fill
any available space so will be the
same volume as its container
 2.
- temperature is the average
energy of motion of the particles of a
substance
(3. Temperature)
- The faster the particles are moving,
the greater their energy and the
higher the temperature
- A thermometer - a speedometer for
molecules!
- Gas molecules at 20o C - travel at
500 meters per second (typically)
4. Pressure
 Gas
particles
- constantly
move &
collide with
each other &
the walls of
their
containers.
(4. Pressure)
 This
results in an outward push by
the gas.
 This outward force is called pressure.
 Pressure
= Force/Area
 Measured
in units of kilopascals(kPa)
Objects like a soccer ball or
balloon, have gas under pressure
inside that keeps them inflated .
This is a
pressurized space
suit.
- What happens if
any of these get a
hole in them?
4. Relating Pressure &
Volume
 Gases
behave in predicable ways.
 Robert Boyle - English scientist in
the 1600’s
 - found that when the pressure of a
gas is increased at a constant
temperature, the volume of the gas
decreases. When the pressure
decreases, the volume increases.
BOYLE’S LAW
 Boyle’s
Law also applies to
situations where volume of a gas
changes.
 Then the pressure also changes.
What would happen
to the pressure & the
volume if you
squeezed one
of these balloons in
your hands?
5. Relating Pressure &
Temperature
 Thought
Exercise:
 Think of a sand storm.
 Would pouring a handful of
sand over your arm feel
different than being in a strong
storm?
 HOW?
The greater the speed of the
sand particles, the more energy
they carry & transfer.
 Gas particles also travel at great
speeds.
 Remember: pressure measures how
much gas particles push outward on
their container.

- the greater the speed of the gas
particles, the greater the pressure.

- Temp. is the average speed of
particles.
Charles’s Law - 1700’s French
Scientist Jacques Charles
 When
the temperature of a gas at a
constant volume is increased, the
pressure of the gas increases.

When the temperature is
decreased, the pressure of the gas
decreases.
Charles’s Law
III. Graphing Gas Behavior
 Graphs
are diagrams that tell how
2 variables or factors are related.

- graphs can be used to make
predictions
Collecting data - use a data table
Data from a
data table can
then be
graphed.
This graph
shows the
linear
relationship
between
temp. &
volume which
are directly
proportional.
This
graph
shows the
relationship
between
pressure
& volume
which
varies
inversely.
IV. Changes of State - physical
change of matter from one state or
phase to another. (ex. solid - liquid)
 A.
Energy & changes in state
 1. A substance changes state when
its thermal (heat) energy increases
or decreases by a sufficient amount.

2. Thermal energy - the energy of
a substances particles

- transferred from one substance
to another
- always flows from a warmer
substance to a cooler substance
 Remember:
the arrangement &
motion of particles in a substance
determine whether substances are
solid, liquid, or gas.
 - particles of solids have the least
thermal energy, gas the most.
B. Changes of State or Phase
 1.
MELTING - solid to liquid
 - melting point of a substance is
determined by how strongly its
particles are attracted.
 - Thermal energy makes
molecules vibrate faster. At a
certain temperature (the melting
point) they can break free.
Melting wax
Melting ice
- ice begins
to melt at 0o
C, the
temperature
at which
molecules
are moving
fast enough
to flow as a
liquid.
Molten silver - What
happens to the molecules
as the metal cools?
Do substances require
the same amount of
thermal (heat) energy
to melt?
THINK of melting:
- water ice
- steel
- plastic
- rock
2. Freezing - liquid to solid
 Liquid
loses energy as it cools.
 Molecules slow down.
 When water reaches 0oC, its
molecules are moving so slowly
that it starts to form into regular
patterns - ice crystals
 This is the same temperature at
which ice melts!
So what does happen to
molten silver molecules
as the metal cools?
3. Vaporization - liquid to gas
 Occurs
when a liquid gains enough
energy to become a gas.
 Two main types:
 - evaporation - molecules on the
surface escape

- ex.s a drying puddle, sweating
 - boiling -takes place inside a

liquid & on the surface
Note: Evaporation happens at the surface &
boiling inside the liquid. Boiling is actually
water molecules turning into a bubble of gas
inside the liquid & then bubbling out as
densities change. Which requires more energy?
- a. boiling point - is the
temperature a which a liquid boils
 Boiling
points of substances:
 - water (at sea level) = 100oC
 - salt = 1413o
 - diamond = 4827oC
 Boiling point is affected by air
pressure. The lower the air
pressure, the less energy is needed
for molecules to escape. Water will
boil at 95oC in Denver, Colorado.
4. Condensation - gas to liquid
 Occurs
when gas particles lose
enough energy to become a liquid.
 - ex.s clouds, mist,breath on a
mirror
 Steam is NOT condensation (water
vapor) but tiny drops of liquid water
suspended in the air.
Water vapor
condensing on a
flower.
This happens when
the water vapor
touches a cooler
surface & loses
thermal energy.
Think of a cold
glass on a humid
day.
Fog - water vapor
cooling & condensing in
the rainforest.
5. Sublimation - solid to gas
 Occurs
when the surface particles of
a solid gain enough energy to
become a gas.
 - particles do NOT pass through a
liquid state.
 Ex.s
- dry ice, naphthalene(moth
balls,) iodine, water ice
Dry ice - CO2
Note that the
fog you see is
not CO2 gas,
(you can’t see
that) - it’s
water vapor
condensing in
the cold
surrounding
the dry ice.
Dry ice - CO2
Sublimating Iodine
Water ice & snow will also sublimate.
How could this happen?
Hint: It happens in very cold places
like Antarctica.
C. Identifying Substances Through
Changes of States/Phase
 The
properties of substances can
help to identify them.
 - boiling/melting points

 If
you were given 3 colorless liquids
you could identify them by their
boiling & melting points.
Freezing - Boiling
•Water
0o
- 100o C
•Ethanol
-117o -
79o
•Chloroform
- 64o
61o
-