Materials Science and Engineering. What is a Material Engineer? Material engineers develop and test...
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Transcript of Materials Science and Engineering. What is a Material Engineer? Material engineers develop and test...
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