Materials Science and
Engineering
What is a Material Engineer?
 Material engineers develop and test new materials for
various uses that help us create a wide range of new
products such as
 Computer chips
 Recreational equipment (i.e. golf clubs, bicycles, skis,
etc.)
 Building materials for cars, aircraft, etc.
 Building materials for houses, skyscrapers, and bridges
What are materials?
 Materials are made of one or more substances.
 A single substance material is a pure substance, while
a material composed of several substances is
classified as a mixture.
 Pure substances are created through chemical
changes; mixtures are created through physical
changes.
 All materials have unique physical and chemical
properties that make them suitable for one application
or another.
Slime is a Unique Material
Slime is a unique POLYMER because it has qualities of both a
solid and a liquid. It can take the shape of its containers like a
liquid does, yet you can hold it in your hand and pick it up like a
solid. As you might know, solid molecules are tight together,
liquid molecules spread out and break apart (drops). As you
will soon learn, POLYMER molecules CHAIN themselves
together (they can stretch and bend like chains) and that gives
them flexibility. Jell-O, rubber bands, plastic soda bottles,
sneaker soles, even gum are all forms of polymers. The
polymer you made should be kept in a sealed plastic bag when
you aren't playing with it. Also, be sure to keep it away from
young kids or pets who might think it's food. Have fun!
Matter
 All materials are made of matter.
 Matter: anything that takes up space and has mass
 Mass: the amount of “stuff” in an object
 Weight: gravity’s pull on mass
 on Earth, this is the same as mass
 Law of Conservation of Matter: “matter cannot be
created or destroyed”…but it can be rearranged (via
chemical or physical reactions, the same as energy)
Atoms
Matter is composed of atoms
 Atoms: The smallest piece of an element
that still retains the properties of that
element
 can not be further divided and still have those
properties
 Are composed of protons, neutrons, and
electrons
Pure Substance
 A substance with uniform and constant
composition (set formula)
 Ex: H2, Cl2, C6H12O6, NaCl, H2O, Fe
 Elements and compounds are both
considered to be pure substances
What is an Element?
 Element: A substance that can not be
changed into a simpler substance(s)
under normal laboratory conditions
 A substance made up of only one type of
atom is an elemental substance
 Material engineers are working on the process of creating
man-made diamonds to be used as superconductors in
electronics. Because diamonds are made of only the
element carbon, they are considered a pure substance.
How do we represent the
elements?
 Represented by symbols on the periodic table
 Usually comes from the name, a person, or a place
 One or two letters for those with official names
 First letter is ALWAYS capitalized
 Second letter is never capitalized
 Unofficially named elements have three letters,
starting with a capital U
The Periodic Table
A highly organized arrangement of the elements
Metals
• Are solids at room temperature (with the exception of
mercury)
• Conduct heat and electricity
• Malleable- can be hammered or pounded into shapes
without breaking
• Have a luster, or shine
• Combine with other metals to make mixtures called
alloys (more on alloys later)
Non-metals
 Mostly gases at room temperature in elemental form
 Poor conductors of heat and electricity (insulators)
 Combine chemically with other non-metals to make
non-metallic compounds
Semi-metals
 AKA metalloids
 Have properties of both
__________________________
 Semi-metals at the _____________ of the table are more
like non-metals
 Semi-metals at the _____________ of the table are more
like metals
The Periodic Table allows us to predict
what type of material an element is.
What is a compound?
 Compound: A substance composed
of two or more elements in fixed
proportions that cannot be broken
down into simpler substances by
physical means.
Compounds
 Two (2) or more DIFFERENT elements
combined in definite proportions
 Has own, unique:
 Formula
 properties
 Boiling point, freezing point, density, etc
 Need a chemical reaction to separate
them into the elements it is made from
 2 H2O -> 2H2 and O2
Properties of Compounds
 properties
differ from those of individual
elements under the same conditions

EX: table salt (NaCl)


Na is a metal
Cl2 is a gas
 Ex: water (H2O)
 H2 is a gas
 O2 also a gas
How do we represent
compounds?
 Chemical formulas show us not only the elements that
make up a compound, but also show us the ratio in
which those elements combine.
 Examples: NaCl, H2O, C6H12O6
 Synthetic (man-made) Rubber is a material
composed of compounds formed between carbon
and hydrogen. When carbon and hydrogen bond
together, the compounds they form have completely
different properties than either elemental carbon or
elemental hydrogen.
Element, Compound, or
Mixture?
1. Vitamin C (C6H8O6)
2. Water
3. Orange juice
4. Iron
5. Steel (iron and carbon)
6. Diamond
7. Concrete
8. Pryex (silicon dioxide and boric oxide)
All materials have unique physical and
chemical properties
 Physical Property
 Characteristic of a substance that can be observed
without changing the identity (formula) of the
substance
 Examples:
 state of matter
 density
 color
 melting pt.
 odor
 boiling pt.
All materials have unique physical and
chemical properties
 Chemical Property
 Ability of a substance to change to a
different substance
 You must change the identity (formula) of
the substance to observe a chemical
property
 Examples:
 flammability
 reactivity with acids and bases
Materials undergo Physical
Changes
 A physical change is a change in the form of the
substance, not in its chemical nature
 No chemical bonds broken or made
 The chemical formula is the same before and after the
change
 The attractions between the molecules are made or broken, not
the molecules themselves
 Examples:
 cutting/tearing
 change in state: melting, boiling,
evaporating, condensing, freezing
 bending
Materials undergo Chemical
Changes
 Change one substance into another
 Atoms are reorganized to make new
substances
 Bonds are broken and reformed in new ways
 Examples:




Burning
Mixing baking soda and vinegar
Digestion
Rusting
Signs of Chemical Change
 Change in:
 Bubbling/ fizzing
 color
 temperature
 Hot (exothermic)
 Cold (endothermic)
 odor
 giving off light
Materials can also be mixtures of
several pure substances
 A mixture is a blend of 2 or more pure substances
 Have variable compositions
 No chemical formula
 If the substances mixed together are only metals,
the mixture is called an alloy.
 Examples:
Steel is a mixture of carbon and iron
Bronze is an alloy of copper and tin
Classification of Matter
How Stuff Works: Steel
1. Steel is a very useful building material. Describe why steel
is such a special material.
1. How can the properties of steel be altered?
1. Where does steel come from?
1. Why is the recycling process so important to the steel
industry?
Alloys
 Created by a mixture of two or more metals
 Why do materials engineers use alloys?



Some alloys are stronger than the individual metal ingredients
Mixing metals results in a substance with altered properties
 Changing density - an engineer can make a material that is lighter or heavier
 Changing flexibility - an engineer can make a material that is more or less rigid
Cost savings (i.e. 14-k gold is less expensive than 18-k gold)
 Disadvantages of alloys



Requires a tremendous amount of energy to make – mixing metals requires that the
metals are molten at the time of mixing
Processing creates a lot of pollution and toxic waste products
Prone to corrosion, so protective coatings are required
More on Alloys: http://www.engr.sjsu.edu/WofMatE/Metals&Alloys.htm
Polymers

Polymers are made of long, chemically bonded chains of atoms.

Usually made of carbon and hydrogen that can be linked in many different ways to make many different types of polymers

Plastics are a type of polymer that are processed by molding and shaping and come in many different types (i.e.
polyethylene and nylon)

Why do materials engineers use polymers?

Polymers are durable – they do not rust or degrade

Polymers are flexible

They can be molded into almost any shape

They can be colored during production, so there is no need to paint

They are recyclable

Disadvantages of polymers

Difficult to produce uniformly
 Contaminated easily during production by even a tiny bit of dirt
 Any variation in heat or molding time can ruin production
More on polymers: http://www.engr.sjsu.edu/WofMatE/polymers.htm
True or False: What do you
think?
1. Polymers are only man-made.
2. Spider silk is stronger than steel.
3. Scientists created nylon while trying reproduce spider
silk in the laboratory.
4. A recycled plastic bottle is only recycled into other
bottles.
Composites
 Made of two or more different materials with distinctly different physical and
chemical properties which remain separate in the finished material
 Doesn’t that mean a composite material is a mixture?

NO! A mixture results when the components are uniformly mixed together. The materials of
a composite are not uniformly mixed together.
 Why do materials engineers use composites?



Have properties that cannot be achieved by any one material alone
Composites materials have a high strength-to-weight ratio
Corrosion resistant
 Disadvantages of composites


Expensive to make
Difficult to repair if damaged because they cannot be reshaped
More on Composites: http://www.engr.sjsu.edu/WofMatE/Composites.htm