PROPERTIES OF MATTER
Chapter Twelve: Properties of
Matter
12.1 Properties of Solids
12.2 Properties of Fluids
12.3 Buoyancy
Chapter 12.1 Learning Goals
Distinguish chemical properties from
physical properties of matter.
Identify differences between
crystalline and amorphous solids.
Explain how the arrangement of
atoms and molecules in solids
determines their properties.
Investigation 12A
Mystery Material
Key Question:
How do solids and liquids differ?
12.1 Properties of Solids
 Different kinds of matter have
different characteristics.
 Characteristics that can you
observe directly are called
physical properties.
 Physical properties include
color, texture, density,
brittleness, and state (solid,
liquid, or gas).
Ex. Iron is solid at
room temp.
12.1 Properties of Solids
 A physical change is any change
in the size, shape, or phase of
matter in which the identity of a
substance does not change.
 For example, when water is
frozen, it changes from a liquid
to a solid.
12.1 Properties of Solids
 Properties that can only be
observed when one
substance changes into a
different substance are
called chemical properties.
 Any change that transforms
one substance into a
different substance is called
IronEx.
reacts
with
oxygen
If you
leave
a nail
a chemical change.
to form
ironitoxide.
outside,
rusts.
12.1 Properties of Solids
The density of a solid
material depends on
two things:
1. the individual mass of
each atom or molecule,
Carbon atoms in
diamond are packed
very tightly.
2. how closely the atoms
or molecules are
packed together.
12.1 Properties of Solids
 Paraffin wax is also
mostly carbon, but its
density is only 0.87
g/cm3.
 Paraffin’s carbon
atoms are mixed with
hydrogen atoms in
long molecules that
take up more space.
The density of paraffin is low
compared to diamond.
12.1 Properties of Solids
The atoms or molecules in a solid are
arranged in two ways.
1. If the particles are arranged in an
orderly, repeating pattern, the
solid is crystalline.
2. If the particles are arranged in a
random way, the solid is
amorphous.
12.1 Properties of Solids
 Examples of
crystalline solids
include salts,
minerals, and
metals.
12.1 Properties of Solids
 Metals don’t look
like “crystals”
because solid
metal is made
from very tiny
crystals fused
together in a
jumble of
different
orientations.
12.1 Properties of Solids
 The atoms or molecules
in amorphous solids
are randomly arranged.
 Examples of
amorphous solids
include rubber, wax,
and glass.
12.1 Mechanical properties
“Strength” describes the ability of a
solid object to maintain its shape even
when force is applied.
12.1 Mechanical properties
Tensile strength is a measure of how
much stress a material can withstand
before breaking.
12.1 Mechanical properties
Hardness measures a solid’s
resistance to scratching.
How might you compare the hardness of these two metals?
12.1 Mechanical properties
Elasticity describes a
solid’s ability to be
stretched and then return
to its original size.
Brittleness is defined as
the tendency of a solid to
crack or break before
stretching very much.
12.1 Mechanical properties
A ductile material can
be bent a relatively large
amount without
breaking.
The ductility of many
metals, like copper,
allow then to be drawn
into wire.
12.1 Mechanical properties
Malleability measures a
solid’s ability to be
pounded into thin
sheets.
Aluminum is a highly
malleable metal.
12.1 Mechanical properties
Almost all solid
materials expand as the
temperature increases.
The increased vibration
makes each particle
take up a little more
Sidewalks and bridges
space, causing thermal have grooves that allow
expansion.
for thermal expansion.
Chapter Twelve: Properties of
Matter
12.1 Properties of Solids
12.2 Properties of Fluids
12.3 Buoyancy
Chapter 12.2 Learning Goals
Explain how pressure is created in
fluids.
Discuss differences between the
density of solids and fluids.
Apply Bernoulli’s principle to explain
how energy is conserved in fluids.
12.2 Properties of Fluids
 A fluid is defined
as any matter that
flows when force
is applied.
 Liquids like water
or silver are kinds
of fluid.
12.2 Pressure
A force applied to a fluid creates
pressure.
Pressure acts in all directions, not
just the direction of the applied
force.
12.2 Forces in fluids
Forces in fluids are more complicated
than forces in solids because fluids
can change shape.
12.2 Units of pressure
The units of
pressure are force
divided by area.
One psi is one
pound per square
inch.
12.2 Units of pressure
The S.I. unit of
force is the pascal.
One pascal (unit
of force) is one
newton of force
per square meter
of area (N/m2).
12.2 Pressure
If your car tires are
inflated to 35 pounds
per square inch (35
psi), then a force of 35
pounds acts on every
square inch of area
inside the tire.
What might happen if you over-inflate a tire?
12.2 Pressure
On the microscopic
level, pressure comes
from collisions
between atoms.
Every surface can
experience a force
from the constant
impact of trillions of
atoms.
This force is what we
measure as pressure.
12.2 Pressure
In a car engine high pressure is created by
an exploding gasoline-air mixture.
12.2 Energy conservation
and Bernoulli’s Principle
Streamlines are
imaginary lines drawn
to show the flow of
fluid.
Bernoulli’s principle
tells us that the energy
of any sample of fluid
moving along a
streamline is constant.
12.2 Bernoulli’s Principle
Bernoulli’s principle says the three
variables of height, pressure, and
speed are related by energy
conservation.
12.2 Three Variables and
Bernoulli’s Principle
If one variable increases along a streamline,
at least one of the other two must decrease.
For example, if speed goes up, pressure
goes down.
12.2 The air foil
One of the most important
The
difference
in
applications
of Bernoulli’s
principle
is is
thewhat
airfoil
pressure
shape of wings on a plane.
creates the lift force
When
a plane is moving,
that supports
the plane
the pressure on the top
in the of
air.the wings is
surface
lower than the pressure
beneath the wings.
12.2 Hydraulics and Pascal’s
Principle
Hydraulic lifts and other hydraulic devices
use pressure to multiply forces and do
work.
The word hydraulic refers to anything that
is operated by a fluid under pressure.
Hydraulic devices operate on the basis of
Pascal’s principle, named after Blaise Pascal.
12.2 Hydraulics and Pascal’s
Principle
Pascal’s principle states that the
pressure applied to an incompressible
fluid in a closed container is
transmitted equally in all parts of the
fluid.
An incompressible fluid does not
decrease in volume when pressure is
increased.
12.2 Hydraulics and Pascal’s
Principle
A small force exerted over a large
distance is traded for a large force
over a small distance.
12.2 Pressure
Pressure is force divided by area.
12.2 Force
You can calculate the force exerted if
you know the pressure and area.
Solving Problems
On a hydraulic lift,
5 N of force is
applied over an
area of 0.125 m2.
What is the output
force if the area of
the larger cylinder
is 5.0 m2?
Solving Problems
1. Looking for:
 …output force
2. Given
 …input force = 5 N; input area = .125 m2
; output area = 5 m2
3. Relationships:
 Pressure = Force Force = P x A
Area
Solving Problems
4. Solution
 Solve for pressure using input force.
 Pressure =
5N
.125m2
= 40 N/m2
 Use Pascal’s law principle and use
equivalent pressure to solve for output
force.
 Force = 40 N x 5 m2 =
m2
200 N
12.2 Viscosity
Viscosity is the property of fluids that
causes friction.
Viscosity is determined in large part
by the shape and size of the particles
in a liquid.
12.2 Viscosity and
temperature
As the temperature of a
liquid increases, the
viscosity of a liquid
decreases.
Increasing the kinetic
energy of the substance
allows the particles to
slide past one another
more easily.
Investigation 12C
Density of Fluids
Key Question:
What is the maximum load a boat can hold before
sinking?
How is the maximum load affected by the density
of the water in which the boat floats?
Chapter Twelve: Properties of
Matter
12.1 Properties of Solids
12.2 Properties of Fluids
12.3 Buoyancy
Chapter 12.3 Learning Goals
Define buoyancy.
Explain the relationship between
density and buoyancy.
Discuss applications of
Archimedes’ principle.
Investigation 12B
Buoyancy of Fluids
Key Question:
Can you make a clay boat?
12.3 Buoyancy is a force
Buoyancy is a measure of the
upward force a fluid exerts on an
object that is submerged.
The water in the pool
exerts an upward
force that acts in a
direction opposite to
the boy’s weight.
12.3 Volume and buoyancy
The strength of the buoyant force on an
object in water depends on the volume of
the object that is underwater.
As you keep pushing downward on the ball, the
buoyant force gets stronger and stronger. Which
ball has more volume underwater?
12.3 Weight and buoyancy
Weight is a force, like any
other pushing or pulling
force, and is caused by
Earth’s gravity.
It is easy to confuse mass
and weight, but they are not
the same.
Weight is the downward
force of gravity acting on
mass.
What is the rock’s
weight?
What is the rock’s
mass?
12.3 Weight and buoyancy
In the third century BC, a
Greek mathematician named
Archimedes realized that
buoyant force is equal to the
weight of fluid displaced by
an object.
A simple experiment can be
done to measure the buoyant
force on a rock with a spring
scale when it is immersed in
water.
12.3 Weight and buoyancy
In air the buoyant
force on the rock is
29.4 N.
When the rock was
submerged, the scale
read 19.6 N.
The difference is a
force of 9.8 N, exactly
the amount of force
the displaced water
exerts.
12.3 Weight and buoyancy
These blocks are the same total volume.
Which block has more buoyant force acting on it?
Which block weighs more in air?
12.3 Weight and buoyancy
Buoyancy
explains why
some objects sink
and others float.
Whether an object
sinks or floats
depends on how
the buoyant force
compares with
the weight.
12.3 Density and buoyancy
If you know an object’s density you
can quickly predict whether it will
sink or float.
Which ball will sink in water?
Which ball will float in water?
12.3 Density and buoyancy
Average density helps determine
whether objects sink or float.
 An object with an average density
GREATER than the density of water will
sink.
 An object with an average density LESS
than the density of water will float.
12.3 Density and buoyancy
What can you say about the
average density of these blocks?
12.3 Density and buoyancy
When
they the
are steel
completely
underwater,
However,
ball has
more
both
balls
have
buoyant
weight
since
it the
has same
a higher
density.
force because they displace the same
volume of water.
12.3 Boats and average density
Use your understanding of average
density to explain how steel boats
can be made to float.
12.3 Boats and average density
If
A you
full ship
havehas
seen
more
a loaded
masscargo
than an
ship,
empty
you
might
ship. have noticed that it sat lower in the
water than an unloaded ship nearby.
This means a full ship must displace more
water (sink deeper) to make the buoyant
force large enough to balance the ship’s
weight.
Investigation 12C
Density of Fluids
Key Question:
What is the maximum load a boat can hold before
sinking?
How is the maximum load affected by the density
of the water in which the boat floats?
The Hull
There are many different
types of boats, but all
have one thing in
common—the hull.
The hull is the main body
of the boat. It displaces
the water that provides
the upward buoyant
force. It also provides
stability.