1. Physical Science Ch. 22

2. Section 1 Materials with a Past

3. AlloyAlloy –a mixture of a metal with one or more elements Have all basic properties of metals: –Luster - a shiny appearance –Ductility - the ability to be pulled into thin wires –Malleability - the ability to be hammered or rolled into thin sheets –Conductivity - the ability to transfer heat and electricity

4. Some different alloysSome different alloys –Bronze a mixture of copper and tina mixture of copper and tin –Brass a mixture of copper and zinca mixture of copper and zinc –Steel processed iron oreprocessed iron ore When an alloy is formed, some of the properties of its components—such as hardness or chemical resistance—may change.When an alloy is formed, some of the properties of its components—such as hardness or chemical resistance—may change. Scientists are always trying to make better alloys with properties superior to those of current alloys.Scientists are always trying to make better alloys with properties superior to those of current alloys.

5. Section 2 Versatile Materials

6. CeramicsCeramics –compounds of metallic elements and oxygen, carbon, nitrogen, or sulphur –Made by shaping the material into the desired shape and then heating to 1,000°C to 1,700°C –The heating process causes the spaces between particles that make up the object to shrink. –The object shrinks and becomes more dense.

7. Common properties of ceramics StrengthStrength Chemical resistance to oxygen, water, acids, bases, saltsChemical resistance to oxygen, water, acids, bases, salts HardnessHardness Do not conduct heatDo not conduct heat Some do conduct electricitySome do conduct electricity Ceramics are so useful and versatile because they can be customized to have a variety of properties.Ceramics are so useful and versatile because they can be customized to have a variety of properties.

8. SemiconductorsSemiconductors –metalloids that are poorer conductors of electricity than metals, but better conductors of electricity than nonmetals –Make computers and other electronic devices possible DopingDoping –Adding impurities to some metalloids can alter their conductive properties. Increasing number of electrons forms an n-type semiconductorIncreasing number of electrons forms an n-type semiconductor decreasing the number of electrons forms a p-type semiconductordecreasing the number of electrons forms a p-type semiconductor An integrated circuit contains many semiconductor devices.An integrated circuit contains many semiconductor devices.

9. Section 3 Polymers & Composites

10. PolymersPolymers –a substance with chain-like molecules composed of small, simple, repeating units called monomers Naturally occurring polymersNaturally occurring polymers –Proteins –Cellulose –Nucleic acids

11. Synthetic polymersSynthetic polymers –manufactured in lab or chemical plant Plastics Synthetic polymersPlastics Synthetic polymers –Do not occur naturally, produced by a chemical reaction Common properties -Lightweight-Strong -Impact resistant-Waterproof -Moldable-Chemical Resistant -Inexpensive

12. Can be blended and customized to have a variety of properties.Can be blended and customized to have a variety of properties. Made from fossil fuelsMade from fossil fuels –Oil –Coal –Natural gas Carbon and hydrogenCarbon and hydrogen –the primary components of synthetic polymers, make up hydrocarbons. Plastics

13. CompositeComposite –a mixture of two or more materials –one embedded or layered in the other –Allows a manufacturer to take advantage of beneficial properties of more than one substance, such as strength, light weight, or flexibility Examples of CompositesExamples of Composites –Fiberglass threads of glass are embedded in plastic to make it strongerthreads of glass are embedded in plastic to make it stronger –Concrete Can put in rebar to strengthenCan put in rebar to strengthen