thecandleover sothatthe wax falls' on theareayouwantsealed.Nowlet the
egg, glass, andtubestandundisturbedovernight.In the morning,breakthe
eggandexaminethe egg white.
Results:Bymorningthe levelofthe fluid in thetubewasabovethesurface
ofthe eggshell.Thewaterin the glass was at a lower levelthanit wasoriginally.
Whenyouexaminedthe egg white it wasmuchthinnerthanordinaryuncooked
egg white.Whatactuallyhappened?
Any living skin tissuewhichis very, verythinis called amembrane.Like all
livingthings,membranesaremadeofcells,the basic structuralunitofplants
andanimals.Membranesr seem to bestrongandsolid,butif youlookedatone
under a microscope, youwouldsee thatthe walls ofthe cells are porous.
Becauseofthesepores,osmosiscantakeplace.Osmosisis theprocessbywhich
moleculespassthroughtheporesin the cell wallsofa membrane.Osmosis,in
otherwords,isdiffusionthrougha membrane.
Inthe experimentwith the egg,watermolecules from theglass ofwater
passedthroughthe thin skinofthe eggandpushedthe egg white upintothe
tube.Actually,while the watermoleculespassedupintothe egg, someofthe
egg white molecules also passeddownintothewater. Butbecausemolecules
move fasterfroma thinliquid,likewater, to athickerone, like egg white,
therewasnotyetenoughegg white in thewaterto be clearly visible.
Theprocessofosmosis is veryimportantinourlivesbecauseall theairwe
breathe,the food we eat,andthe wastesourbodiesmustremovepassthrough
the cellmembranesin thismanner.
ANOTHER WAY OF OBSERVING OSMOSIS
Gather these materials:Twothistletubesor small glassfunnels;2 pintjars;
2 uprightstandsandclamps;3 testtubes;analcoholburner;sometransparent
cellulosewrappingpaper;2 Tubberbands;sucrose(C12H 22011 ) ; crystalsof
coppersulfate(CuS0 4 ) ;andsomeBenedict'ssolution.
Follow this procedure: 1.Firstyouwill have to learnhow to test for the
presenceofsugar,becauseyouwill need to know thislaterin theexperiment.
LabelthejarsI and2. FilljarNo. I halfwaywithwarm water.Dissolve 3
teaspoonfulsofsugarin thewater.Nowpoura littleofthesugarsolutionintoa
testtubeand add3 teaspoonfulsofBenedict'ssolution.Heatthe testtubeover
the alcoholburneruntil the liquidboils. Nowplace 2teaspoonfulsofplain
waterin a fresh test tubeand addan equalamountofBenedict'ssolution.
Heatthe testtubeover thealcoholburneruntiltheliquidboils.
Results:When youboiledthesugarsolutionwithBenedict'ssolutionadded,
it turnedbrickred.ThecoloroftheplainwaterwithBenedict'ssolutionadded