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科学计数法
和有效数字运算
2ScientificNotationThenumberofatomsin12gofcarbon:602,200,000,000,000,000,000,0006.022x1023Themassofasinglecarbonatomingrams:0.00000000000000000000001991.99x10-23Nx10nNisanumberbetween1and10nisapositiveornegativeinteger
3ScientificNotation568.762n0568.762=5.68762x102movedecimalleft000=7.72x10-6movedecimalrightAdditionorSubtractionWriteeachquantitywiththesameexponentnCombineN1andN2Theexponent,n,remainsthesame4.31x104+3.9x103=4.31x104+0.39x104=4.70x104
4ScientificNotationMultiplicationMultiplyN1andN2Addexponentsn1andn2(4.0x10-5)x(7.0x103)=(4.0x7.0)x(10-5+3)=28x10-2=2.8x10-1DivisionDivideN1andN2Subtractexponentsn1andn28.5x104÷5.0x109=(8.5÷5.0)x104–9=1.7x10-5
MeasurementandSignificantFiguresEveryexperimentalmeasurementhasadegreeofuncertainty.Thevolume,V,atrightiscertaininthe10’splace,10mLV20mLThe1’sdigitisalsocertain,17mLV18mLAbestguessisneededforthetenthsplace.
Belowaretwomeasurementsofthemassofthesameobject.Thesamequantityisbeingdescribedattwodifferentlevelsofprecisionorcertainty.
7SignificantFiguresAnydigitthatisnotzeroissignificant1.234kg4significantfiguresZerosbetweennonzerodigitsaresignificant606m3significantfiguresZerostotheleftofthefirstnonzerodigitarenotsignificant0.08L1significantfigureIfanumberisgreaterthan1,thenallzerostotherightofthedecimalpointaresignificant2.0mg2significantfiguresIfanumberislessthan1,thenonlythezerosthatareattheendandinthemiddleofthenumberaresignificant0.00420g3significantfigures
8Howmanysignificantfiguresareineachofthefollowingmeasurements?24mL2significantfigures3001g4significantfigures0.0320m33significantfigures6.4x104molecules2significantfigures560kgambiguous
Once
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