2What 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
3What 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.
4Slime 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!
5Matter All materials are made of matter. Matter: anything that takes up space and has massMass: the amount of “stuff” in an objectWeight: gravity’s pull on masson Earth, this is the same as massLaw of Conservation of Matter: “matter cannot be created or destroyed”…but it can be rearranged (via chemical or physical reactions, the same as energy)
6Atoms Matter is composed of atoms Atoms: The smallest piece of an element that still retains the properties of that elementcan not be further divided and still have those propertiesAre composed of protons, neutrons, and electrons
7Pure SubstanceA substance with uniform and constant composition (set formula)Ex: H2, Cl2, C6H12O6, NaCl, H2O, FeElements and compounds are both considered to be pure substances
8What 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 substanceMaterial 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.
9How 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 capitalizedUnofficially named elements have three letters, starting with a capital U
10The Periodic Table A highly organized arrangement of the elements
11Metals Are solids at room temperature (with the exception of mercury) Conduct heat and electricityMalleable- can be hammered or pounded into shapes without breakingHave a luster, or shineCombine with other metals to make mixtures called alloys (more on alloys later)
12Non-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
13Semi-metals AKA 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
14The Periodic Table allows us to predict what type of material an element is.
15What 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.
16CompoundsTwo (2) or more DIFFERENT elements combined in definite proportionsHas own, unique:FormulapropertiesBoiling point, freezing point, density, etcNeed a chemical reaction to separate them into the elements it is made from2 H2O -> 2H2 and O2
17Properties of Compounds properties differ from those of individual elements under the same conditionsEX: table salt (NaCl)Na is a metalCl2 is a gasEx: water (H2O)H2 is a gasO2 also a gas
18How 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, C6H12O6Synthetic (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.
19Element, Compound, or Mixture? Vitamin C (C6H8O6)WaterOrange juiceIronSteel (iron and carbon)DiamondConcretePryex (silicon dioxide and boric oxide)
20All materials have unique physical and chemical properties Physical PropertyCharacteristic of a substance that can be observed without changing the identity (formula) of the substanceExamples:state of matterdensitycolormelting pt.odorboiling pt.
21All 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 propertyExamples:flammabilityreactivity with acids and bases
22Materials undergo Physical Changes A physical change is a change in the form of the substance, not in its chemical natureNo chemical bonds broken or madeThe chemical formula is the same before and after the changeThe attractions between the molecules are made or broken, not the molecules themselvesExamples:cutting/tearingchange in state: melting, boiling,evaporating, condensing, freezingbending
23Materials undergo Chemical Changes Change one substance into anotherAtoms are reorganized to make new substancesBonds are broken and reformed in new waysExamples:BurningMixing baking soda and vinegarDigestionRusting
24Signs of Chemical Change Change in:Bubbling/ fizzingcolortemperatureHot (exothermic)Cold (endothermic)odorgiving off light
25Materials can also be mixtures of several pure substances A mixture is a blend of 2 or more pure substancesHave variable compositionsNo chemical formulaIf 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
27How Stuff Works: SteelSteel is a very useful building material. Describe why steel is such a special material.How can the properties of steel be altered?Where does steel come from?Why is the recycling process so important to the steel industry?
28Alloys Created by a mixture of two or more metals Why do materials engineers use alloys?Some alloys are stronger than the individual metal ingredientsMixing metals results in a substance with altered propertiesChanging density - an engineer can make a material that is lighter or heavierChanging flexibility - an engineer can make a material that is more or less rigidCost savings (i.e. 14-k gold is less expensive than 18-k gold)Disadvantages of alloysRequires a tremendous amount of energy to make – mixing metals requires that the metals are molten at the time of mixingProcessing creates a lot of pollution and toxic waste productsProne to corrosion, so protective coatings are requiredMore on Alloys:
29Polymers 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 polymersPlastics 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 degradePolymers are flexibleThey can be molded into almost any shapeThey can be colored during production, so there is no need to paintThey are recyclableDisadvantages of polymersDifficult to produce uniformlyContaminated easily during production by even a tiny bit of dirtAny variation in heat or molding time can ruin productionMore on polymers:
30True or False: What do you think? Polymers are only man-made.Spider silk is stronger than steel.Scientists created nylon while trying reproduce spider silk in the laboratory.A recycled plastic bottle is only recycled into other bottles.
31CompositesMade of two or more different materials with distinctly different physical and chemical properties which remain separate in the finished materialDoesn’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 aloneComposites materials have a high strength-to-weight ratioCorrosion resistantDisadvantages of compositesExpensive to makeDifficult to repair if damaged because they cannot be reshapedMore on Composites: