Thermal ExpansionHole SizeMicroscopic SpacingChange in VolumeCoefficient of Volume ExpansionGas TankCold WaterStretching SolidsLinear ExpansionSeasonal ChangesThermal StressThermal ExpansionThermal ExpansionHole SizeHole SizeA rectangular sheet of metal has a circular hole. What A rectangular sheet of metal has a circular hole. What happens to the size of the hole when the metal is happens to the size of the hole when the metal is heated?heated?A) It gets larger.A) It gets larger.B) It gets smaller.B) It gets smaller.C) It stays the same.C) It stays the same.Microscopic SpacingMicroscopic SpacingAtoms are in constant Atoms are in constant motion.motion.•Vibration increases with Vibration increases with temperaturetemperature•Spacing increases with Spacing increases with temperaturetemperatureChange in VolumeChange in VolumeThe volume of matter The volume of matter expands when the atomic expands when the atomic spacing increases.spacing increases.•Increase temperature Increase temperature →→ increase volume.increase volume.A volume increase is the A volume increase is the same as a density decrease.same as a density decrease.TVV 0TVT + TV + VCoefficient of Volume Coefficient of Volume ExpansionExpansionFor small volume changes For small volume changes the relationship between the relationship between volume and temperature is volume and temperature is linear.linear.The coefficient of volume The coefficient of volume expansion is expansion is ..MaterialMaterialCoefficient Coefficient QuartzQuartz1 x 101 x 10-6-6 CC-1-1 Pyrex glassPyrex glass9 x 109 x 10-6-6 CC-1-1 GlassGlass27 x 1027 x 10-6-6 CC-1-1 SteelSteel35 x 1035 x 10-6-6 CC-1-1 AluminumAluminum75 x 1075 x 10-6-6 CC-1-1 MercuryMercury180 x 10180 x 10-6-6 CC-1-1 WaterWater210 x 10210 x 10-6-6 CC-1-1 GasolineGasoline950 x 10950 x 10-6-6 CC-1-1 Ethyl alcoholEthyl alcohol1100 x 101100 x 10-6-6 CC-1-1 AirAir (1 atm) (1 atm)3400 x 103400 x 10-6-6 CC-1-1 TVV 0Gas TankGas TankA 72 L steel gas tank is open A 72 L steel gas tank is open and filled to the top with and filled to the top with gasoline, gasoline, = 950 x 10 = 950 x 10-6-6 CC-1-1, , at 18 at 18 C. The car sits in the C. The car sits in the sun and reaches a sun and reaches a temperature of 32 temperature of 32 C.C.How much gasoline How much gasoline overflows from the tank?overflows from the tank?The gasoline expands with The gasoline expands with temperature.temperature.Solve for Solve for VV = = VV00 T.T.((950 x 10950 x 10-6-6 CC-1-1)(72 L)(14 )(72 L)(14 C)C)VV = = 0.95 L0.95 LThe tank expansion was The tank expansion was small in comparison.small in comparison.You get more gas if you fill it You get more gas if you fill it when it’s cool!when it’s cool!Cold WaterCold WaterMost substances expand Most substances expand uniformly with temperature.uniformly with temperature.Water does not follow the Water does not follow the pattern.pattern.•Below 4 Below 4 C water expands C water expands as it coolsas it cools•Very cold water stays on topVery cold water stays on top•Ice is even less denseIce is even less denseStretching SolidsStretching SolidsTLT + TL + LSolids can have dimensions Solids can have dimensions that are quite different.that are quite different.The long dimension may The long dimension may matter most.matter most.•Focus on one dimensionFocus on one dimension•Other changes are still Other changes are still present, less magnitudepresent, less magnitudeLinear ExpansionLinear ExpansionThe change in volume The change in volume applies to the three applies to the three dimensions.dimensions.If the change is equal in all If the change is equal in all directions directions is split in thirds. is split in thirds.The coefficient of linear The coefficient of linear expansion in solids (expansion in solids () is ) is usually one third of usually one third of ..WHLHWLWLHVWHLV0000000000)3()3()3(000000000WTHLWHTLWHLTV3/0 LTLSeasonal ChangesSeasonal ChangesThe steel bed of a The steel bed of a suspension bridge is 200 m suspension bridge is 200 m long at 20 long at 20 C.C.If the temperature goes from If the temperature goes from -30 -30 C to +40 C to +40 C, what C, what contraction and expansion is contraction and expansion is possible?possible?Use linear expansion.Use linear expansion.Solve for Solve for LL = = LL00 T.T.First in winter,First in winter,((12 x 1012 x 10-6-6 CC-1-1)(200 m)(-50 )(200 m)(-50 C)C)LL = = -0.12 m-0.12 mThen in summer,Then in summer,((12 x 1012 x 10-6-6 CC-1-1)(200 m)(20 )(200 m)(20 C)C)LL = = 0.048 m0.048 mThermal StressThermal StressA change in length is A change in length is associated with a stress.associated with a stress.Temperature change causes Temperature change causes a change in length.a change in length.If the stress is due to If the stress is due to temperature, it’s a thermal temperature, it’s a thermal stress.stress.next0LLYAF
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