ofthe two typesofcrystal. Put a smallquantityofeach intoseparatetest tubes.
Heatthem one at a time for several minutes over the alcohol burner.Atthe
end of this time, write adescriptionof eachsubstanceandcompareit with the
originaldescription.Allow the test tubes to cool.Put1 or 2dropsof water in
each tube.Noteand recordthe result.
Results: The crystals became powderyand/orlost their color when you
heatedthem. Theyregainedtheir originalcolorandform when youlateradded
water.
When crystalscontainingwater ofhydrationareheated,the water molecules
evaporate,and thesubstancechanges inappearance.Itbecomespowderyand
if it wascolored,it loses its color. Since it becomes powdery, it isapparentthat
waterofhydrationhelps to hold the atomsofcrystals in aparticularpattern.
When the water is replaced, the crystals regain theiroriginalcolorand form.
HOW YOU CAN DISCOVER AND USE EFFLORESCENCE AND
DELIQUESCENCE
Gather these materials:A kitchen scale delicateenoughto record the weight
of3 teaspoonfulsofa chemicalsalt;crystallinesodiumcarbonate(Na2COa) ;
solid pellets ofsodiumhydroxide(NaOH);filterpaper;andpaperand pencil.
Follow this procedure: Write adescriptionof the appearanceof each sub-
stance. Put 3teaspoonfulsofeach chemical on 2 different pieces of clean filter
paperand weigh eachpaper.CAUTION:Do not let thesodiumhydroxidetouch
yourskin.Ifit does, wash itimmediatelywith lots ofcool water. Record the
weights of each paper. Now spread thesubstancesout, each on its own filter
paper,and let them stand overnight. Weigh them in the morning. Record the
changes.