A first general chemistry laboratory experiment

A First General Chemistry Laboratory Experiment

~.~

.

Plannine the exoeriment for the first ehemistrv laboratow is a difficult undertakine. because of the crp:tt ;u14011111 (11time !wrled for wg~!tirhrlmnlrnattcr.~n l d 11.r innldily of t l w ..tlldrnts t u pn!p:drc ~hwlts~lve.. fur a n y ~ ~ l w l v ernn!.~pkll:~tionr. d At \Y:~4.ln.mi-r~ivrr.~lvwe lmve f ~ u t . dthe vrry.wrrc..4~lfor he ~ w t t IaLora~ory. ~l f ~ , l l ~ , s . ~ n g r x ~ , r r . i ~-ttbje:tive~ ~ t ! ~ ~ t oljet ~~vcpn,prrticr After the organizational business and safety lectwes have been completed, each student is given a form with ten numbered blanks. He is asked to describe briefly, but accurately, the colors of five samples and the odors of another five chemicals. The instructor collects and tabulates the class resdts while the students determine the densitv of water mine a. eradoated cvlinder and a m

~

~

~~

closed in parentheses, from an average elasa of 20:

Color: Sodium uranyl acetate (8); copper(1) chloride (14); hylviolet dye (9); copper(I1) acetate meta arsenete (13); and ammoniwn copper(I1) chloride (11). Odor: Phenol (12); camphor (9); iso-amyl acetate (11); oil of saflrole (10); and Lranscinnamaldehyde (8). The remainder of the period is used for a discussion of the difference between objective and subjective properties and significant figures. I t is interesting to point out the female effect on subjective properties; that is, girls always list a greater variety of colors and odors than their male classmates. Although this experiment is extremely simple, it dramatizes the difficulty of using subjective properties to describe chemicals.

H. COHEN SHELDON E. ZABEL DOUGLAS D. SHORES RICHARD WA~HBWEN UNIVERSITY TOPEKA,KANSAS66621

66

/

Journal of Chemical Education