chemistry experiments for children

the litmus paper. When theamountof change begins to become very small
use only I drop of alkali at a time.Continueuntil you reach thepointwhere
there is no changeatall in the litmus paper.
Results:The change in colorofthe blue litmus to red became less and less
marked as you added more alkali to the acid. This showsthattheadditionof
an alkali was making thesolutionless and less acid. Finally, you reached a
point where the solution had no effect whatsoever on the colorofthe litmus
paper. This was theend point,or point ofneutralization.Enough alkali had
been added sothatthe solution was definitely no longer acid; it had been
neutralizedby the alkali. If you had continued to add alkali to thesolutionafter
reaching the end point, it would slowly have turned into an alkali, and you could
have traced its progress by testing it with red litmus paper. Theequationfor the
neutralizationin this experiment is:
2CHaCOOH+Ca(OH)z-+2H 20 +Ca(CHaCOO)z
The neutralized liquid is a calcium acetate solution. In a much moreelaborate
form, the processofgradual neutralizationandcontinuoustesting which you
performed in this experiment is calledtitration.Chemists often usetitrationto
tell exactly how many H atomsand/orOH radicals are present in a solution.
This isimportantin medicine, in the dye and drug industries, and even in
preparingthe paints for anartist'spalette or for your house.