Chapter 9:
Heat and States of Matter
Section 2: States of Matter
States of Matter
2
Four States of Matter
SOLID STATE
• The particles of a
solid are packed
closely together
and are constantly
vibrating in place.
• The attractions between particles are strong
and solids have a fixed volume and shape.
States of Matter
2
LIQUID STATE
• The attractive
forces are strong
enough to cause
particles to cling
together.
• Liquids have a
definite volume,
but not a definite
shape.
States of Matter
2
GAS STATE
• In a gas the forces
between particles
are so weak that the
particles no longer
cling together.
• Gases do not have
a definite shape or
volume.
States of Matter
2
Plasma State
• The most common state of matter
in the universe is the plasma state.
• PLASMA is matter consisting of
positively and negatively charged particles
and does not have a definite shape or
volume.
States of Matter
2
Changing States
Melting
• The temperature at which a solid begins
to melt is its melting point.
• The amount of energy required to change
1 kg of a substance from a solid to a liquid
at its melting point is known as the HEAT
OF FUSION.
States of Matter
2
Freezing
• The HEAT OF FUSION is also the energy
released when a liquid freezes.
• The attractive forces are strong enough that
the particles form an ordered arrangement.
States of Matter
2
Vaporization
• Vaporization occurs as liquid changes
into a gas.
• Vaporization that occurs at the surface
of a liquid is called evaporation.
• Evaporation causes the temperature
of the liquid to decrease.
• Can you explain this?
States of Matter
2
Boiling
• The BOILING POINT of a liquid is the
temperature at which the pressure of the
vapor in the liquid is equal to the external
pressure acting on its surface.
• The HEAT OF VAPORIZATION is the
amount of energy required for 1 kg of the
liquid at its boiling point to become a
gas.
States of Matter
2
CONDENSATION
• The HEAT OF VAPORIZATION is also the
amount of energy released during condensation.
• This graph
shows the
temperature
change of
water as
thermal energy
is added.
States of Matter
2
CONDENSATION
• The average kinetic energy of the
water molecules doesn’t change.
• The temperature
remains constant
during melting.
What about during
evaporation?
States of Matter
2
CONDENSATION
• After the liquid water has changed
completely into a gas, the temperature
of the gas
increases as
energy is added.
States of Matter
2
Thermal Expansion
THE THERMAL EXPANSION OF MATTER
• The increased separation between the
particles results in the expansion of the
object and the size of the object increases.
• When a material cools, the particles in the
material move more slowly and become
closer together.
2
States of Matter
THERMAL EXPANSION OF LIQUIDS
• The forces between the particles in liquids are
weaker than the forces between the particles in
a solid.
• The same temperature increase usually causes
liquids to expand much more than solids.
2
States of Matter
THERMAL EXPANSION OF GASES
• In a gas, the forces between particles are much
weaker than they are in liquids.
• Gases expand even more than liquids for the
same increase in temperature.
Section Check
2
Question 1
_________ is a state of matter consisting of
positively and negatively charged particles that
exists where the temperature is extremely high.
A.
B.
C.
D.
Gas
Liquid
Plasma
Solid
Section Check
2
Answer
The answer is C. Plasma is found in the Sun,
stars, lightning bolts and neon lights.
Section Check
2
Question 2
Most __________ materials have a specific
type of geometric arrangement.
A.
B.
C.
D.
gaseous
inert
liquid
solid
Section Check
2
Answer
The answer is D. The particles in most solids
align themselves in ordered geometric patterns.
Section Check
2
Question 3
The amount of energy required to change 1 kg
of a substance from a solid to a liquid at its
melting point is known as the _______.
A.
B.
C.
D.
heat of energy
heat of fusion
heat of melting
heat of vaporization
Section Check
2
Answer
The correct answer is B. Heat of fusion causes
an ice cube to become liquid water.