Properties of Matter
Solids, Liquids, and Gases
Promotion Benchmark 9 Lesson Review
Student Copy
Vocabulary
Solid – A state or phase of matter that has a definite shape and a definite volume.
Liquid – A state or phase of matter that has a definite volume but no definite
shape.
Gas – A state or phase of matter that has no definite shape or volume.
Phase change – A change of matter from one phase to another.
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County School Board of Fairfax County, VA
2005
IV – 128
Science 8 Review
Review for Promotion Benchmark 9:
Describes the properties of a solid, liquid and a gas; explains
the effect of heating or cooling on the states of matter
The matter around you is made up of moving molecules in the form of
solids, liquids, and gases. The form that matter takes depends on its shape and
volume. Solids have a definite shape and a definite volume. The molecules in a
solid are packed closely together. Although the molecules in a solid are moving,
they are so close to one another that they don’t look like they are moving at all.
They basically vibrate in their place. An ice cube, the table, the floor, and a metal
bar are all examples of solids. A liquid has a definite volume but no definite
shape. Liquid molecules are also packed closely together, but there is enough
space between the molecules to allow them to slide past each other. This sliding
action prevents the liquid from taking a shape of its own. As a result, liquids take
the shape of the container that holds them. Some examples of liquids are water,
milk, bleach, blood, and mercury (liquid metal). A gas has no definite shape and
no definite volume. The molecules in a gas are spaced farther apart, and they
move very rapidly. Gas molecules move to fill up the size of their container, like
when you blow up a balloon. Some examples of gases are water vapor, air, carbon
dioxide, ozone, and oxygen.
©
County School Board of Fairfax County, VA
2005
IV – 129
Science 8 Review
Example:
Water Molecule
Solid
Liquid
Gas
Closely packed; Barely Moving
Loosely Packed; Sliding Past
Free Floating; Moving Fast
A phase change is a change in the state of matter from one form to another.
There are four types of phase changes: melting, boiling or vaporizing,
condensing, and freezing. An example of melting is when a solid changes to a
liquid. When thermal energy is added to an ice cube, its molecules begin to move
faster. This creates more space between the molecules and allows them to slip past
each other changing the ice into water. If more thermal energy is added, the
molecules in the water further increase their motion. This causes the water to boil
or vaporize and turn into water vapor, a gas. Phase changes also result when
thermal energy is removed from matter. When a gas such as water vapor is cooled,
it condenses or changes into water, a liquid. The removal of thermal energy
allows the molecules to slow their kinetic motion. As the molecules slow down,
they pack more closely together and change the state of matter. Another phase
change occurs when a liquid changes to a solid, or freezes. Freezing is the result
©
County School Board of Fairfax County, VA
2005
IV – 130
Science 8 Review
of removing thermal energy from a liquid. As the molecules slow down, they pack
closer together and form a solid, such as when water turns to ice.
Usually, the addition or removal of thermal energy from a substance will
result in a change in the average kinetic motion of the molecules, or temperature,
of the substance. During a phase change, however, the thermal energy being used
to change the state of matter will not cause a change in the temperature of the
substance. The energy being added or removed from the system is being used to
break or form the molecular bonds holding the molecules together. As a result, the
temperature will remain steady, or reach a plateau, during a phase change.
Solid
Melting
Boiling/Vaporizing
Phase Change
Phase Change
Thermal energy
added
Tightly packed
molecules, hardly
moving
Liquid
Liquid
Loosely packed
molecules, sliding
past
Loosely packed
molecules, sliding
past
Phase Change
Free moving
molecules,
moving fast
©
Thermal energy
taken away
Gas
Free moving
molecules,
moving fast
Freezing
Condensing
Gas
Thermal energy
added
Phase Change
Liquid
Liquid
Loosely packed
molecules, sliding
past
Loosely packed
molecules, sliding
past
County School Board of Fairfax County, VA
2005
IV – 131
Thermal energy
taken away
Solid
Tightly packed
molecules, hardly
moving
Science 8 Review
The Properties
of Matter
Solid
Definition
Molecules
look like
Liquid
Definition
Molecules
look like
(draw a picture)
Phase Change
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County School Board of Fairfax County, VA
Gas
Definition
(draw a picture)
Phase Change
Molecules
look like
(draw a picture)
Phase Change
2005
IV – 132
Science 8 Review
Review for Promotion Benchmark 9
Directions: Match the word with the definition
1. ______ A change of matter from one phase to
A.
Solid
2. ______ Has no definite shape or volume
B.
Liquid
3. ______ A change from a liquid to a solid
C.
Gas
4. ______ Has a definite shape and volume
D.
Phase change
5. ______ A change from a solid to a liquid
E.
Freezing
6. ______ Has a definite volume and no definite
F.
Melting
G.
Boiling
another
shape
7. ______ A change from a liquid to a gas
©
County School Board of Fairfax County, VA
2005
IV – 133
Science 8 Review