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1、ReviewofChemistryDerivedQuantitiesDefinitions:ADERIVEDQUANTITYisanumbermadebycombiningtwoormoreothervalues.ADERIVEDUNITisaunitwhichismadebycombiningtwoormoreotherunits.II.4DensityDefinition:Mass=thequantityofmatteronanobjectDensity=themasscontainedinagivenvolumeofasubstanceII.5Significantf
2、iguresandexperimentaluncertaintySIGNIFICANTFIGURESA.Asignificantfigureisameasuredormeaningfuldigit.B.Anaccuratemeasurementisameasurementthatisclosetothecorrectoracceptedvalue;aprecisemeasurementisareproduciblemeasure.C.Thenumberifsignificantfiguresisequaltoallthecertaindigitsplusthefirstun
3、certaindigit.D.“Defined”numbersand“counting”numbersareassumedtobeperfectedsothattheyare“exempt”fromtherulesapplyingtosignificantfigures.BEVERUCAREFU;WHENAVLAUEAPPEARSTOCOINCIDEEXACTLYWITHAMARKINGONAMEASURINGDEVICE.Thefollowingprocedureshouldhelpwhensuchasituationoccurs.THEPROCEDUREFORCORRE
4、CTLYREADINGMEASURINGSCALESWHENAPOINTERISEXACTLYONANUMBEREDDIVISIONlDeterminethevaluethatthemeasurementseemstohave.lPretendyouhaveavalueinbetweentwooftheunnumberedsubdivisionsonyourmeasuringdevice.lDeterminehowmanydecimalplacesyoucouldreadoffthemeasuringdeviceatthe“in-betweenvalue”.lAddasuf
5、ficientnumberofzeroestotheactualreadingtogiveyouthecorrectnumberofdecimalplacesforyourreading.EXPERIMENTALUNCERTAINTYDefinition:Theexperimentaluncertaintyistheestimatedamountbywhichameasurementmightbeinerror.E.Whenaddinganuncertaintytoameasurement,theuncertaintygoesafterthemeasuredvaluebut
6、beforetheunit.NOTE:Iftheuncertaindigitisinthefirstdecimalplace,theuncertaintywillbeinthefirstdecimalplacealso.INTERPRETATIONOFUNCERTAINTIESIMPORTANT:Theplacevalue(tens,units,firstdecimal,etc.)oftheexperimentaluncertaintyandthefirstuncertaindigitofameasurementmustagreewitheachother.F.NORMAL
7、LYUSEUNCERTAINTIESTOTHENEAREST0.1OFTHESMALLESTUNNUMBEREDSUBDIVISION.Ifyoucanonlyestimateavaluetothenearest0.2oreven0.5ofthesmallestunnumberedsubdivision,feelfreetodoso,butbepreparedjustifyyourdecision.G.Leadingzeroesarenotsignificant.H.Trailingzeroesareallassu
