Materials Science and Engineering

1. Materials Science and Engineering

2. What is a Material Engineer? • Material engineers develop and test new materials for various uses that help us createa 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

3. 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.

4. 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!

5. 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)

6. 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

7. 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

8. 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.

9. 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

10. The Periodic TableA highly organized arrangement of the elements

11. 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)

12. 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

13. 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

14. The Periodic Table allows us to predict what type of material an element is.

15. 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.

16. 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

17. 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

18. 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.

19. Element, Compound, or Mixture? • Vitamin C (C6H8O6) • Water • Orange juice • Iron • Steel (iron and carbon) • Diamond • Concrete • Pryex (silicon dioxide and boric oxide)

20. 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.

21. 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

22. 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

23. 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

24. Signs of Chemical Change • Change in: • Bubbling/ fizzing • color • temperature • Hot (exothermic) • Cold (endothermic) • odor • giving off light

25. 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

26. Classification of Matter

27. How Stuff Works: Steel • Steel 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?

28. 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

29. 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

30. True 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.

31. 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