2.2 Physical Properties
There are pitchers of ice water and lemonade
on a picnic table. How do you know which
liquid is in each pitcher? It’s easy! Lemonade
is yellow and has a tart taste that is hard to
miss. A yellow color and a tart taste are two
properties of lemonade.
2.2 Physical Properties
Examples of Physical Properties
What are some examples of physical
properties?
A physical property is any characteristic of a
material that can be observed or measured
without changing the composition of the
substances in the material.
Viscosity, conductivity, malleability,
hardness, melting point, boiling point, and
density are examples of physical properties.
2.2 Physical Properties
Examples of Physical Properties
Viscosity
The tendency of a liquid to
keep from flowing is called its
viscosity.
• Thick liquids, such as corn
syrup and honey, have a high
viscosity.
• Thin liquids, such as vinegar
and water, have a low
viscosity.
2.2 Physical Properties
Examples of Physical Properties
Conductivity
A material’s ability to allow heat to flow
is called conductivity.
• Materials that have a high conductivity,
such as metals, are called conductors.
• Good conductors of heat are usually also
good conductors of electricity.
2.2 Physical Properties
Examples of Physical Properties
Malleability
The ability of a solid to be hammered without shattering is
malleability.
• Most metals, such as gold, are malleable.
• An ice cube or piece of glass breaks into small pieces when
struck with a hammer. Solids that shatter when struck are brittle,
not malleable.
2.2 Physical Properties
Examples of Physical Properties
Hardness
One material can scratch another material if it
is harder than the other material.
• A kitchen knife can scratch a copper sheet
because stainless steel is harder than copper.
• The material used to sharpen the knife blade
must be harder than stainless steel. Diamond is
the hardest known material.
2.2 Physical Properties
Examples of Physical Properties
This Tlingit carver is using an adze to carve a canoe from
Western red cedar. Red cedar is a relatively soft wood.
The adze is hard.
2.2 Physical Properties
Examples of Physical Properties
Melting and Boiling Points
The temperature at which a material changes
state is a physical property.
• The temperature at which a substance changes
from solid to liquid (melts) is its melting point.
• The temperature at which a substance changes
from liquid to gas (boils) is its boiling point.
2.2 Physical Properties
Examples of Physical Properties
Melting and Boiling Points
Which of these substances are liquids
at room temperature (20C, or 68F)?
Answer:
2.2 Physical Properties
Examples of Physical Properties
Melting and Boiling Points
Which of these substances are liquids
at room temperature (20C, or 68F)?
Answer: octane,
water, and
acetic acid
2.2 Physical Properties
Examples of Physical Properties
Density
The ratio of the mass of a substance to its
volume is its density.
• Density can be used to test the purity of a
substance.
• Silver has a density of 10.5 g/cm3. A coin with a
density of 9.9 g/cm3 is not made from silver, or it
contains substances in addition to silver.
2.2 Physical Properties
Using Physical Properties
How can knowing the physical properties of
matter be useful?
Physical properties are used to identify a
material, to choose a material for a specific
purpose, or to separate the substances in a
mixture.
2.2 Physical Properties
Using Physical Properties
Using Properties to Identify Materials
A material can be identified by its
properties.
• Decide which properties to test.
• Do tests on a sample of the unknown
material.
• Compare the results with the data reported
for known materials.
2.2 Physical Properties
Using Physical Properties
Using Properties to Choose Materials
Properties determine which materials are
chosen for which uses.
• For example, shoelaces must be flexible,
that is they must be able to bend without
breaking.
• They must also be durable, that is, they
must be able to withstand repeated use.
2.2 Physical Properties
Using Physical Properties
Laces in hiking boots are usually made of
nylon or leather, not from wood.
2.2 Physical Properties
Using Properties to Separate Mixtures
What processes are used to separate
mixtures?
Filtration and distillation are two common
separation methods.
2.2 Physical Properties
Using Properties to Separate Mixtures
Filtration
You can separate hot tea from loose tea
leaves by pouring the mixture through a
strainer. Filtration is a process that
separates materials based on the size of
their particles.
2.2 Physical Properties
Using Properties to Separate Mixtures
These students filter (sift) dirt through a
wire screen to locate small objects.
Particles of dirt are small enough to pass
through the holes, but objects such as
broken bits of pottery are too large.
2.2 Physical Properties
Using Properties to Separate Mixtures
Distillation
Sometimes all the particles in a solution
are small enough to pass through a filter.
Distillation is a process that separates
the substances in a solution based on
their boiling points.
2.2 Physical Properties
Recognizing Physical Changes
The change of water from a liquid to a gas
during boiling is a physical change. A
physical change occurs when some of the
properties of a material change, but the
substances in the material remain the same.
2.2 Physical Properties
Recognizing Physical Changes
During a physical change, the size and
shape of a material can change but not the
composition. Some examples include
• melting butter in a pan
• crumpling a piece of paper
• slicing a tomato
2.2 Physical Properties
Recognizing Physical Changes
Some but not all physical changes can be
reversed. Braiding hair is a reversible
change. Cutting hair cannot be reversed.
2.2 Physical Properties
Assessment Questions
1. Which of the following is not a physical property?
a.
b.
c.
d.
density
boiling point
flammability
conductivity
2.2 Physical Properties
Assessment Questions
1. Which of the following is not a physical property?
a.
b.
c.
d.
density
boiling point
flammability
conductivity
ANS: C
2.2 Physical Properties
Assessment Questions
2. Which of these materials is not malleable?
a.
b.
c.
d.
copper
aluminum
glass
gold
2.2 Physical Properties
Assessment Questions
2. Which of these materials is not malleable?
a.
b.
c.
d.
copper
aluminum
glass
gold
ANS: C
2.2 Physical Properties
Assessment Questions
3. In choosing a material for use as a wire to carry
electric current, which physical property would be
most important?
a.
b.
c.
d.
conductivity
malleability
hardness
boiling point
2.2 Physical Properties
Assessment Questions
3. In choosing a material for use as a wire to carry
electric current, which physical property would be
most important?
a.
b.
c.
d.
conductivity
malleability
hardness
boiling point
ANS: A
2.2 Physical Properties
Assessment Questions
4. Which of these statements best describes a physical
change in a pure substance?
a. The substance changes into one or more new substances.
b. Some of the properties of the substance change, but the material
remains the same.
c. The properties of the material do not change, and the material
remains the same.
d. The substance is separated into two or more simpler substances.
2.2 Physical Properties
Assessment Questions
4. Which of these statements best describes a physical
change in a pure substance?
a. The substance changes into one or more new substances.
b. Some of the properties of the substance change, but the material
remains the same.
c. The properties of the material do not change, and the material
remains the same.
d. The substance is separated into two or more simpler substances.
ANS:
B
2.2 Physical Properties
Assessment Questions
1. The process of filtration uses the difference in
boiling points of substances to separate a mixture.
True
False
2.2 Physical Properties
Assessment Questions
1. The process of filtration uses the difference in
boiling points of substances to separate a mixture.
True
False
ANS:
F, distillation