Physical SciencePhysical Science

Ch. 22Ch. 22

Section 1Section 1

Materials with a PastMaterials with a Past

• AlloyAlloy–a mixture of a metal with one or more a mixture of a metal with one or more

elementselements

Have all basic properties of metals:Have all basic properties of metals:–LusterLuster - a shiny appearance - a shiny appearance–DuctilityDuctility - the ability to be pulled into - the ability to be pulled into

thin wiresthin wires–MalleabilityMalleability - the ability to be - the ability to be

hammered or rolled into thin sheetshammered or rolled into thin sheets–ConductivityConductivity - the ability to transfer - the ability to transfer

heat and electricityheat and electricity

• Some different alloysSome different alloys– BronzeBronze

• a mixture of copper and tina mixture of copper and tin– BrassBrass

• a mixture of copper and zinca mixture of copper and zinc– SteelSteel

• processed iron oreprocessed iron ore• When an alloy is formed, some of the When an alloy is formed, some of the

properties of its components—such as properties of its components—such as hardness or chemical resistance—may hardness or chemical resistance—may change.change.

• Scientists are always trying to make Scientists are always trying to make better alloys with properties superior to better alloys with properties superior to those of current alloys.those of current alloys.

Section 2Section 2

Versatile MaterialsVersatile Materials

• CeramicsCeramics–compounds of metallic elements compounds of metallic elements

and oxygen, carbon, nitrogen, or and oxygen, carbon, nitrogen, or sulphursulphur

–Made by shaping the material Made by shaping the material into the desired shape and then into the desired shape and then heating to 1,000°C to 1,700°Cheating to 1,000°C to 1,700°C

–The heating process causes the The heating process causes the spaces between particles that spaces between particles that make up the object to shrink.make up the object to shrink.

–The object shrinks and becomes The object shrinks and becomes more dense.more dense.

Common properties of ceramicsCommon properties of ceramics• StrengthStrength• Chemical resistance to oxygen, Chemical resistance to oxygen,

water, acids, bases, saltswater, acids, bases, salts• HardnessHardness• Do not conduct heatDo not conduct heat• Some do conduct electricitySome do conduct electricity• Ceramics are so useful and Ceramics are so useful and

versatile because they can be versatile because they can be customized to have a variety of customized to have a variety of properties.properties.

• SemiconductorsSemiconductors– metalloids that are poorer conductors of metalloids that are poorer conductors of

electricity than metals, but better electricity than metals, but better conductors of electricity than nonmetalsconductors of electricity than nonmetals

– Make computers and other electronic Make computers and other electronic devices possibledevices possible

• DopingDoping– Adding impurities to some metalloids can Adding impurities to some metalloids can

alter their conductive properties.alter their conductive properties.• Increasing number of electrons forms an Increasing number of electrons forms an

n-type n-type semiconductorsemiconductor• decreasing the number of electrons forms a decreasing the number of electrons forms a

p-type p-type semiconductorsemiconductor

• An integrated circuit contains many An integrated circuit contains many semiconductor devices.semiconductor devices.

Section 3Section 3

Polymers & CompositesPolymers & Composites

• PolymersPolymers–a substance with chain-like a substance with chain-like

molecules composed of small, molecules composed of small, simple, repeating units called simple, repeating units called monomersmonomers

• Naturally occurring polymersNaturally occurring polymers–ProteinsProteins–CelluloseCellulose–Nucleic acidsNucleic acids

• Synthetic polymersSynthetic polymers–manufactured in lab or chemical manufactured in lab or chemical

plantplant• Plastics Synthetic polymersPlastics Synthetic polymers

–Do not occur naturally, produced by Do not occur naturally, produced by a chemical reactiona chemical reaction

Common propertiesCommon properties-Lightweight-Lightweight -Strong-Strong-Impact resistant-Impact resistant -Waterproof-Waterproof-Moldable-Moldable -Chemical Resistant-Chemical Resistant-Inexpensive-Inexpensive

• Can be blended and customized to Can be blended and customized to have a variety of properties.have a variety of properties.

• Made from fossil fuelsMade from fossil fuels–OilOil–CoalCoal–Natural gasNatural gas

• Carbon and hydrogenCarbon and hydrogen– the primary components of synthetic the primary components of synthetic

polymers, make up hydrocarbons.polymers, make up hydrocarbons.

PlasticsPlastics

• CompositeComposite–a mixture of two or more materialsa mixture of two or more materials–one embedded or layered in the otherone embedded or layered in the other–Allows a manufacturer to take Allows a manufacturer to take

advantage of beneficial properties of advantage of beneficial properties of more than one substance, such as more than one substance, such as strength, light weight, or flexibilitystrength, light weight, or flexibility

• Examples of CompositesExamples of Composites–FiberglassFiberglass

• threads of glass are embedded in threads of glass are embedded in plastic to make it strongerplastic to make it stronger

–ConcreteConcrete• Can put in rebar to strengthenCan put in rebar to strengthen