describe what you know about materials.

Material Properties

S.T.E.M. I

In your notebooks
describe what you
know about
materials.

Material Properties

•
Physical

•
Mechanical

•
Chemical

•
Optical

•
Acoustical

•
Electrical

•
Magnetic

•
Thermal

Physical Properties

•
Gives the material its size, density and
surface texture.

Mechanical Properties

•
Strength

–
Tension

–
Compression

–
Shear

–
Torsion

•
Elasticity:

The ability to
stretch or flex but return to an
original size and shape

•
Plasticity:

The ability to flow
into a new shape under pressure
and to remain in that shape when
the force is removed



•
Hardness:

The ability to resist
cuts, scratches and dents


•
Toughness:
The ability to
resist breaking


•
Fatigue:
The ability to resist
constant flexing or bending

Thermal Properties

•
Thermal properties control how the material
reacts to heat or cold

–
Expansion

–
Contraction

•
Thermal conductivity is a measure of how
easy heat flows through a material

Chemical Properties

•
The materials chemical properties affect how
it reacts to its surroundings.

–
Steel Rusts

–
Glass becomes pitted

–
Plastics become etched and brittle

•
The material is changed by its environment
this reaction is called corrosion.


Question:

How do we protect objects from
corrosion?


Answer:

By coating them with oil, grease,
paint or varnish

Optical Properties

•
Optical properties are a materials reaction to
light

–
When a material stops light we say it is
opaque

–
When a material allows light to pass through we
say it is
translucent

•
The color of a material affects its ability to
absorb or reflect light


Question:

Why is a dark interior of a car
uncomfortable on a hot day?


Answer

The dark color absorbs the light
making the interior hot

Acoustical Properties

•
Acoustical properties in a material control
how it reacts to sound waves

•
All sound energy is produced by vibrations

•
The speed of sound in a material depends on
the spacing of molecules and how easy the
molecules move


Question:

Will sound travel faster in
aluminum or pine and why?


Answer:

Aluminum, because the molecules in
aluminum are closer together

Electrical Properties

•
Some materials conduct electricity and
others do not.


–
Materials that are able to conduct electricity are
called
conductors
.

–
Materials that are unable to conduct electricity
are called
insulators.

•
Semiconductors are materials that allow
electricity to flow under certain conditions

–
Silicone

–
Germanium

Question:

What materials make good
conductors

Answer:

Gold, Silver, Copper, Aluminum

Magnetic Properties

•
A magnetic material will be attracted to a
magnet


–
Iron

–
Nickel

–
Cobalt

–
As well as their alloys

Materials

•
Wood

–
Hardwood: Comes from trees
that shed their leaves.

•
Ebony

•
Oak

•
Maple

•
Beech

•
Cherry

–
Softwood: Comes from trees
that produce cones. (Conifer)

•
Pine

•
Redwood

•
Fur

•
Spruce

•
Plastic

–
Physical Properties

•
Transparency

•
Flexibility

•
Elasticity

•
Permeability

•
Water Resistant

•
Electrical Resistance

–
Chemical Properties

•
Chemical resistance

•
Thermal stability



Materials

•
Paper

–
Interwoven Fibers

–
Wood

–
Cotton

–
Pliable

–
Categorized by Weights


•
Ceramics

–
Crystalline compounds of
metallic and nonmetallic
elements. Ceramics are the most
rigid of all materials with an
almost total absence of ductility.
They have the highest known
melting points of materials with
some being as high as 7,000
°
F
(3,870
°
C) and many that melt at
temperatures of 3,500
°
F
(1,927
°
C). Glass, brick, cement
and plaster, dinnerware, art
ware, and porcelain enamel are
all examples of ceramics.

Metals

•
Metallic luster (shine)

•
Generally solids at room temperature

•
Malleable
-

Something that can be hammered,
pounded, or pressed into different shapes without
breaking.

•
Ductile
-

Capable of being drawn into thin sheets or
wires without breaking.

•
Conduct heat and electricity

•
Combine with other metals to form alloys which
have metallic characteristics


Aggregate:
a component of a composite
material used to resist compressive stress.

•
Gravel

•
River Sand

•
Quarry Sand

•
Brick Bats

•
Granular Slag

•
Poultry Sand

Solvents

•
Can be a solid, liquid or gas used for
testing and cleaning


Adhesives

•
An adhesive, or glue, is a
mixture

in a
liquid

or semi
-
liquid state that
adheres

or bonds
items together. Adhesives may come from
either natural or
synthetic

sources. The types
of materials that can be bonded are vast but
they are especially useful for bonding thin
materials. Adhesives
cure

(harden) by either
evaporating a solvent or by chemical
reactions that occur between two or more
constituents.

Questions?