to combiningchemically, that is, when there is no chemicalchange in the
moleculesofthe substances involved). Diffusion also occurs whenanyfluid or
solid dissolves in a fluid. Thus diffusion can result ineithera suspensionora
true solution.
HOW YOU CAN OBSERVE OSMOSIS
Gather thesematerials:Several fresh,uncookedeggs; a glass tubeordrinking
straw;a small glass (just the right size to hold an egg, butnotlargeenoughto
let the egg fallin);a penkmfe ; and a candle.
Follow this procedure: Noticethatthe two endsofanegg are notexactly
alike. One end is more roundedthanthe other. Chooseone egganddecide
which end isrounder. Using thepointof the sharpedgeofyour penknife,
scrape the eggshell on theroundedend until you can see a thin skinon the
inside. There is onethinskin directlyattachedto the shell and anotherabout
t ofan inch beneathit. You cannothelp breakingthe first skin, butdon't
breakthe second one. Now carefully chip off the eggshell until ithasa hole
slightly smallerthana dime. Thecontentsofthe egg will notdropoutif you
haven'tbrokenthe inside skin. If you have, put the egg aside,returnit toyour
mother(she can still use it for cooking), and try again withanotheregg.Don't
bediscouragedif you breakthe inside skin on several eggs. This requires
patienceand a steadyhand.Practice helps, too.
When you have succeeded in thispartofthe experiment, fill thesmallglass
with water, and set the egg on the rim so thatthe open hole isbeneaththe
surfaceofthe water.Take your penknife again, and in thepointedendofthe
egg, make a very small hole, deeperthantheotherone. Make thisholego right
into the egg white. This hole will be easier to make because youdon'thave to
worryaboutbreakingthe skin. Put one endofthe glass tube ordrinkingstraw
into the egg whitethroughthis second hole. Make theopeningaroundthe tube
airtightby sealing the space between the eggshellandthe tube withcandlewax.
You can do this by lighting a candle and, when the wax begins to melt,tipping
,
~.'.\';' ;...
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