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 asComputer chipsRecreational 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 MaterialSlime 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!

MatterAll 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)

AtomsMatter 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 SubstanceA 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 conditionsA 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 tableUsually comes from the name, a person, or a

placeOne or two letters for those with official

namesFirst letter is ALWAYS capitalizedSecond letter is never capitalized

Unofficially named elements have three letters, starting with a capital U

The Periodic TableA 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-metalsMostly 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-metalsAKA metalloids

Have properties of both __________________________Semi-metals at the _____________ of the table are

more like non-metalsSemi-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.

CompoundsTwo (2) or more DIFFERENT elements

combined in definite proportionsHas own, unique:

Formulaproperties

Boiling point, freezing point, density, etc

Need a chemical reaction to separate them into the elements it is made from2 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 gasO2 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 PropertyCharacteristic of a substance that can be observed

without changing the identity (formula) of the substance

Examples:state of matterdensitycolormelting pt.odorboiling pt.

All materials have unique physical and chemical properties

Chemical PropertyAbility of a substance to change to a

different substanceYou must change the identity

(formula) of the substance to observe a chemical property

Examples:flammabilityreactivity with acids and bases

Materials undergo Physical Changes

A physical change is a change in the form of the substance, not in its chemical natureNo 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/tearingchange in state: melting, boiling,

evaporating, condensing, freezingbending

Materials undergo Chemical Changes

Change one substance into another

Atoms are reorganized to make new substancesBonds are broken and reformed in new ways

Examples:BurningMixing baking soda and vinegarDigestionRusting

Signs of Chemical ChangeChange in:

Bubbling/ fizzingcolortemperature

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 compositionsNo chemical formula

If the substances mixed together are only metals, the mixture is called an alloy.

Examples:Steel is a mixture of carbon and ironBronze is an alloy of copper and tin

Classification of Matter

How Stuff Works: Steel1. Steel is a very useful building material. Describe

why steel is such a special material.

2. How can the properties of steel be altered?

3. Where does steel come from?

4. 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