review of chemistry1

《review of chemistry1》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

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