Scien&ficMeasurements:Length,Mass,Volume,andDensity

SIUnitsofMeasurement•  Manyoftheunitsyou’refamiliarwith(inches,feet,anddegreesFahrenheit)arenotusedinscience.

•  Scien&stsuseasetofmeasuringunitscalledSI,ortheInterna&onalSystemofUnits(alsoknownasthemetricsystem)

•  Whydoyouthinkweusethemetricsystem?

Measurements&Units

•  Forameasurementtomakesense,itneedsanumberandaunit

BaseUnits

•  Thereare7metricunits,knownasbaseunits

Length

•  Themeteristhebasicunitoflengthinthemetricsystem

•  1meter=39.4inches•  Tomeasurelongerdistances,youusethekilometer– Thereare1000metersinakilometer

Length(con:nued)

•  Metersaredividedintocen,meters–  thereare100cen&metersinameter–  tomeasuresomethingsmallerthanameter,youwouldusecen&meters

•  Cen,metersaredividedintomillimeters

Mass&Weight•  Mass:theamountofmaQerinanobject– Ex:atruckhasmoremassthanatoycar

•  Massisnotthesameasweight•  Weightisyourmassmul&pliedbygravity– Yourweightisameasureofhowmuchgravityispullingyoudown

Volume•  Volume:amountofspaceanobjecttakesup•  Theliteristhebasicunitofvolume•  Themilliliteristheunitforsmallvolumesofliquid•  Thecubiccen-meter(cm3)istheunitforsmallvolumesofsolid,orliquid.

Density

•  Density:themasspervolumeofanobject

MetricPrefixes

DerivedUnits

•  Addi&onalSIunits,calledderivedunits,aremadefromcombina&onsofbaseunits

•  Forexample:– Volume:theamountofspaceanobjecttakesup– Density:ra&oofobject’smasstoitsvolume

DerivedUnits•  Specificcombina&onsofSIbaseunitsmakederivedunits.

Density•  Density:themasspervolumeofanobject•  DensityisacomparisonofhowmuchmaQerthereisinacertainamountofspace.

Whichoneismoredense?

Whichoneismoredense?

•  Nowwhichoneismoredense?

LiquidLayers

•  Ifyoupourtogetherliquidsthatdon’tmixandhavedifferentdensi&es,theywillformliquidlayers.

•  TheliquidwiththehighestdensitywillbeontheboQom.

•  Theliquidwiththelowestdensitywillbeonthetop.

LiquidLayers•  Checkoutthispicturefromyourbook.Whichlayerhasthehighestdensity?

•  Whichlayerhasthelowestdensity?•  Imaginethattheliquidshavethefollowingdensi&es:–  10g/mL. 3g/mL.–  6g/mL. 5g/mL.

•  Whichnumberwouldgowithwhichlayer?

LiquidLayers–Trywithyourneighbor

•  Whichliquidhasthehighestdensity?

•  Whichliquidhasthelowestdensity?

•  Whichliquidhasthemiddledensity?