P AR T
2
Exercises in the Scientific Method
-----------------------------------------------------------------------------INTRODUCTION
T o be a co mpet en t, well trained chemist is o ne thi ng . To have a good job , one with
pl en ty o f res ponsibi lity- and the salary th at goes with it-is quite a different matter .
~J O\I begi nni ng studen ts. and even some seniors , think that in college the ir most
import ant task is to master their major subject vcr y well, and to do only the mini mum
req ui red in their non major su b jects, suc h as Engl ish , and all the others. Th is may be tru e
for some of t hese ot her courses, although yO UI' author ,v'o uld arg ue the contrary. but it
certain ly is no t true of English.
Believe it or not , it i... a well-establishe d fact that y Oli will no t progr ess to the top of the
lad der in ch emistry, med icin e, eng ineering, physics, math ematics, or any o ther su bject ,
unless you kn o w well how to usc the English language. ' True, you will probably never
starve: you will even be able to afford a fine steak d inn er once in a while if your command
of your mot her to ng ue is less than excelle nt . But, barring nepot ism , you will not attain a
posit io n of responsibi lit y.
If th is is your am b itio n, to just ge t by. to be med iocre, the n YO ll will no t get from t his
co urse all that it has to offer. Our task for th e tim e re mai n ing to us in th is co urse is th ree fold :
I. T o help you learn how to thi nk.
T o help yo u learn how to express those th o ughts dearly in wr iti ng .
3. T o learn chem istry.
<)
It
For an yone with at least a normal amount of am bition it will not be d ifficu lt, although
will seem so occasio nally.
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NOW LET'S DIG IN!
Beginning- on page 37 man y different prob lems are listed. You r instructor will separate the cia...... into grou p'" o f two students each an d assign seve ra l problem s to each pair of
stu den ts. Yo u will begin by working, with your partn er, on on e of you r assigned problems.
Obviously. wh en o ne pro ble m is co mp le ted you sho u ld sta n on an ot her. It is possib le to
wor k on two or more problem s at the same tim e, and you are encouraged to d o so. Emphasis
is placed in th is co urse on qua lity, net quantity; th is is true. Hu t when it is possib le LO
increase the quant it y o f work do ne without sacrificing q ua lity , an d you do S0, surely YO UT
grade will no t suffer. Fu rther , your inst ru ctor is human, and although he will try to keep
in mind th e h igh q uality of th ose two p roblem s you completed d u ri ng- the who le year, he
is bound to also think wel l of th e fello w on th e opposite be nch who com ple ted a p ro blem
c\'ery two weeks or so, eve n if the q ual ity of his work \.. . as not q u ite th e eq ual of yours,
Your instruc tor will hel p you ge t sta rted on the first problem . H e will suggest that
certain pieces o f a ppa rat us be arranged in a part icu lar way, that certa in solu tions be prepared. that th e reagen ts a nd a ppara tm be mani pu lated in a certa in manner. Pay atte nt ion
to his instructions and ask as man y intelli gent q uestions as yo u wish.
After you have once set up the equipment and materials and gone through the ncces..ar y
manipulations in th e laboratory, attend to the question accompan ying the descr iption of
your problem in this manu al. Yo u r job is to suggest a testa ble answer to th is question an d
then to prove yo u r answer correct or incorrect. The same cred it is awarded for proving you r
answer inco rrect as for the co nve rse. Emphasis is placed upon co nce iving a testable answe r
and u po n the Iimc..s of th e tests whi ch you d evise to de term ine the valid ity of you r answer.
So after the problem is assigned and the d et ails ex plained to YOll. per form the mani pu lat ions req u ired and the n examine the q uest ion . Refer to the tex t yo u use in the lecture
..cssio ns of your chemisu-y class; spend a few ho urs study ing addit ional text s and reference
works; d iscu ss the q ue stion with you r fellow clas..mate.. and wit h anyone else who will Ii..te n ,
O f cou rse your instructor will always be ab le 10 hel p you. H e can su ggest that part icu lar
books be ..t ud icd : he can hel p you decide what to do in the labora tory, provide d that /)efo f('
yOll seek his assistan ce you have clone som e wo rk, some study ing Oil you r own. so that yOll
and he can di scus .. the <I ue..tion in tellige ntl y. As a min imum , you sho uld be able to tell YO UT
instructor wha t yo u have learn ed in your own ..mdics and how yo u think a testable answer
to th e question mi gh t be fou nd .
Also. each week yo u and the ot he r stu d ents in the laboratory will meet as a grou p
for a mutual d iscussion o f your laborator y problem s. Come to th ese me et in gs prepared
to explain yo u r problem d earl y enough so tha t you r fello w studen t.. can understa nd ~"our
d ifficu lt ies an d olTer hel pful suggest ions. Co nversely. as ano ther student d escribes hi .. d illicu h ics, try to thin k of ideas whi ch may hel p him . The more you kn ow about yo ur probl em .
th e ~',-ea ter the probabilit y that you will be able to hel p someone else.
However , your goal is to wri te a report. Aft er yo u have carried out the ma ni pu lat io ns
or iginally detailed b y yo ur inst ructor, after you have u nd erstood the q uest ion , and perhaps,
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A L W A YS wit h the PRIO R approval of you r inst ructor,
afte r you ha ve carried out in the laboratory a few var iations of the original details, after
yo u have stud ied you r tex t and a few references in the library or elsewhere , after you have
d iscussed yo ur problem with others and as a res ult have co nce ived a testable an swer an d
co nd ucted you r tests, yo u and your partner will each wr ite a report. A report is d ue
each week, at th e begin ning of the laborator y pe ri od. If your work on a problem is not
co mpleted, the report wh ich you prepare will necessarily consist of less than the five parh
listed bel ow. I n suc h cases the re po rt d ue the follo wing wee k m ay begin wh ere th is week's
repo rt left off unless your instructor ha s req uested that the cu rren t report be rewrit ten.
A partial report m ay consist of only Part I, Parts I and II , Parts I, II , and III (the se
pa rts are described bel ow) or Parts I, II , III , and I V, but it may not consist o f, say, only Parts
I and II I. T hat is, a partial report must be in order u p to the highest n u mbered par t, un less
it is a co n tinuation of a previously accepted partial report. I n this case, of course, the report
may begin at th e point where the prev ious re port left off. Bu t it mus t also be in orde r ,
lowest to highest n u mbered part, as has been stat ed.
Th e com plete report will consist of five parts:
I. T he phenomenon we observed: Describ e, as co nc isely as possib le, the p heno menon
o bserved when you carried out the manip ula tions d irected. That is, sim ply state, in pla in
language, what ha ppened. T his part is to be writte n in the pa st tens e,
II. T he jJTohlem to he solved . State the q uestion ; copy it word for word from the page.
III. O ur hy J)othesis. State in onc sentence, and it m ust be in one sentence , you r answer
to the q uest ion. You ma y supple ment this statement with an eq uation to show what you
t hink happened . Bu t if yo u can not state yo ur idea in one sentence it is a su re sign that you
d o not kno w yo u r h ypothesis well enough to test it. Also, be su re that your answer to th e
q uest io n is stated so as to be testa bl e. Recall ing, for a momen t, our q uestion : " W hy do
people occasionally become ill?," one co uld no t sugges t th at bacteria caused d isease u nless he
knew how to test for the presence o f bacteria. (This was one o f the reasons that the badblood theory o f di sease 'was no t d iscar ded sooner . Severa l ima ginative think er s suspected the
p resence o f m in u te l iving organ isms in a di seased body, but the y could no t test th is guess
u ntil t he m icroscope was perfected. H ence prio r to its perfection, no one wo uld listen to
the ir h ypothesis, and r ightly so. It was, at that time , just an other wild guess, and th ere wer e
plen ty of these. T here st ill are , in fact. )
I V. Proposed test of
O llr
hY/JotheJis. T hi s part should be divid ed in to two sect ions.
Section ( I) . Begi n with a paragr aph or two, stat in g in some detai l, or in ge ne ra l,
as you think best , how you propose to test the valid ity of you r h ypo thesis. Often it is
hel pful (to you r grade, that is) also to state why you p ropose that a certain p ro ced ure
be used. It is usua lly good to show the reaso ning you have followed in deci d ing u po n
th e tests you now propo se to perform . H owever, tr y to be brief. Ce r tain ly these paragraphs in Section (1) should no t ord inari ly compr ise more than 300 to 500 word s, and
oflen much less will be su ffic ient.
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Secti on (2). I n d etai l, list the ste ps to be foll owed. State th ese d irect ions clea rly
and concisely- so clearly and concisely th at another student (if you r ins tr uctor so chose)
co uld carry ou t the proced ure by followin g' yo u r d irect ions. T his ca n best be accotnpl ishcd if yo ur d irect io ns are a series o f short sen tences in the im perat ive mode. Section
(2) sho uld, sim ply, te ll the laboratory worker wha t to do and what to look for. Be sure
that yo u r proposed tests fit your hypo thesis, that they are consonant with your an swer
to your q ue st ion . For exam ple, if your h ypo the sis on t he cause o f di sease im plies t ha t
peop le occasionall y become ill because they d o not eat n ut rit ious foods, do not ou tli ne
a test wh ich req uire s tha t the di seased organ ism be exam ined for th e p resence or absen ce
o f bac ter ia. H owever , if yo ur h ypothesis is bolder, and sugges ts that d isease is ( I) du e
to poor n u tri tion and (2) not d ue to bacte ria, then a test for bacteri a an d for n ut r it ional
deficiencies would be in ord er because [Jolh tests would be im plied by the bolder
h ypo th esis.
Briefly, then, this is what you should do :
Examine yo ur h ypoth esis carefu lly.
Determ ine what tests it implies.
Descri be these tests in d etai l.
V. Validation 0/ o nr h ypo thesis. T ell what happen ed whe n yo u made you r tests and
state a conclusion : "T he h ypothesis is proved incorrect ," or, "T he h ypothesis was not
p roved inco rrect an d is, the refore , ten ta t ively accepted as the correct explanat ion ."
Ab ove all , do no t sta te this sort of conclusio n : "T he hypothesis was proved correc t and
is, t herefore, the co rrect ex planat ion." For it cou ld be that some one else, in attempting to
solve the same pro blem , m igh t co nceive of an ex pla natio n q u ite d ifferent from your hypothesis and might con duct tests wh ich d id not d isprove h is h ypothesis. H ence if you r h ypoth esi...
and h is were both stated to be correct (that is, thc tests condu cted d id not d isprove eith er
hypo thesis) someth ing would be wro ng. O ne of yon , at least, wou ld be su re to be ill error.
and more tests wou ld be re q uire d to disp rove at least one of the h ypotheses.
Th is has, a... a matt er of fact , happ en ed o ften in the histor ical deve lo pment of science.
T wo conflict ing h ypotheses, neith er of wh ich were d isproved by the tests conducted to
validate t he m , have existed " side by side." Ult imately , of course, one or bo th were d isp ro ved
by more thorough testing , b u t at the time p r ior to d i... p roo f, both were tenta tivel y accepted
as possible co rrect ex plana t ions, even though ever yone knew that at least on e of rh e in had
to be wrong.
T he grade g iven to your report will bc based upo n these poin ts:
I.
2.
3.
4.
5.
6.
T hc reaso nableness of th e h ypo thesis,
The con gruence of the testing- pl an wit h the h ypot hesis.
Th e lISC o f good English gramm ar.
T he clar ity, the u ud crstand ab ilit v, of your exposit ion.
You r laboratory tech niq ue.
T he correct usc of your laborator y not ebook (sec be low).
Xotice in part icu lar that no d ed uct ion is made if you pr m 'c you r h ypothe sis wr on g.
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Fu r ther, no ded uction is made if you did not get you r pro bl em solved as soo n as so me other
grou p in the laborator y. Emphasis is placed u pon the qua l ity of the work you do com plete.
not u pon how man y problem s yOli so lved du ring th e co urse.
Aft er you r report has been su b m itted and graded ; or, bett er yet, before t his, in ord er to
keep busy in the labora tory, you an d your part ner will start on the next p ro blem . Yo ur
instructor will assist you with the in itial detai ls, as before.
H owever, if you fou nd the p roblem just completed to be part icularl y in teresti ng an d
wish, no w that it is for mally comple ted, to p ursu e it fu rt her , prepare a wr-i tte n jus ti ficat ion
of this desire an d pr esent it to you r inst r uctor. It will be nece ssar y that th is writte n pr oposal
d ea rl y state the new q uestion that yo u propose to ans wer. If you r instru ctor thin ks t ha t
ad di tio nal work will be bene ficial to yo u, he will gran t perm ission to co n ti nu e.
Also, after you have had some experience with a few problem s yo u wi ll find it even more
in teresti ng to post ulate two, or eve n more, d ifferent h ypotheses to ex plain the same problem .
If yo u choose to do this, title you r Part I V o f the report, " Pro posed T est to Di stingui sh
amon g (or between , as appro pria te) O u r H ypo theses." You are enco u ra ged to conceive
more tha n one h ypothesis in answer to a q ue stion. It will increase yo u r u nderstand ing 0 1"
the su bject and it certa inly will promote the rare faculty o f open-minde dn ess.
T he last point wh ich demands atten tio n is the laborato ry no tebook. Before the next
laborato ry period , procure a noteboo k with page s prefera bly bou nd by a sewn th read . T he
notebook sho uld be abou t 21.5 by 28 ern in size and sho uld conta in at lea st 50 pages.
X u m ber the pages co nsecut ively from first to last. On the fi rst page wri te you r name,
the ti tle of th is course, a nd th e date you first started to usc the not ebook. (Later, when it is
fi lled , add the date the not ebook was last used , procu re anothe r notebook, and make similar
en tries in it.) On the next two pag-es write "T able of Contents" at the top. O n page 2 (the
fi rst Ta ble of Co ntents page] ,vtr ite:
T ille page
T ab le 01 Co nt ents _
P ro b le m I :
1
2
.,
_
\ \ll1 el1 yo ur first problem is selected , en ter a brief d escr iptive t itle (in your own word s)
aft er the words " Problem 1." On pag e 4, at th e top of the page . write th e same brief dcscriptin t itle. Also, at the top of this page write down the d ate you sta rted to work Oil th is
probl em .
YO II wi ll pro ba bly fill ill several pages as you work on yo u r first problem . Pill the
brief d escrip tive t itle of yo ur problem at the top of each such pagc and, each d ay, wr ite d o ~\'ll
the da te on which you did the work , or study ing , tha t is described in your notes o n t hat page.
As you r instruct or assists you in sett ing lip your fi rst problem , ma ke notes o f h is rem arks
on pag'e 1 of th e notebook. If necessar y, of course , no tes can also be entered O il pag'e 5, 6,
e tc. \ Vhen yOIl execute the ma n ipu la tion s required, ente r ill the notebook a d escript io n of
what ha p pe ned . If yOIl make an y involved mathema tical calcu lat ions , su mmarize the m in
you r notebook, be ing su re to label the n u mbers so th at you can te ll wha t they mean late r.
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If you do, and yo u almost certa inly will do , some outside reading about your problem .
make ent r ies in yo u r no tebook, su mmar izing the important aspects of what is rea d . In these
cases. be sure to also record th e source ; Li H the tid e of the book. th e au thor, p ubli..her.
co p yr ight date . vol u me n umber if the book is one of a set, and of co u rse, the pag-e number..
where the material studi ed was fou nd in the book . Agai n, always he su re th at the b rief
dcsct-iprive titl e o f you r proble m is at th e top of eac h page in the no tebook . He su re to reco rd
t he date on wh ich yo n too k th e no tes from th e reference.
" 'hen you d eci de u po n a hypo th esis. wr ite it in the notebook . If you later deci de n po n
ano ther , wr ite it in too . A ~ you plan t he test o f th e h ypothesis, wr ite the deta ils down in the
no tebook.
I n other word s, you r not ebook should consritu tc a complete wr itten record of all yOll
have do ne . o f all yotl have rea d . of all you yoursel f have tho ugh t, about your probl em .
Except for in volved mat hemat ical calcu lations, never, never , never make a note 0 11 a
loose shee t of paper, th in king later to w py it in to your no tebook. :-\0 harm will result . and
you will proba bly break th is rule almost as o ften as you keep it. But it is po ssible to lo-c
th ose loose sheet s o f paper ; it is less likely th at yo u will lose a bulk y no teboo k. T r y to
establish a habit o f keeping all yo ur records, from th e fi rst mom ent, in the less-easil v-lo..t
notebook. Yo ur au tho r kn ows from bitter expe r ience the value of th is ha bit.
Alway.. bring your notebook with you to the labo rato ry (ob viously), to the weekly
meetings with you r fellow students, an d to your conferences with your instructor. He will
occasiona lly ask a q uest io n, as he help" you , that can best be ans wered by referen ce to the
no tebook.
Do not co ncern yo urself with the legibili ty of th e entr ies in yo ur no tebook. .\I ake them
a" legibl e as you ca n, o f co u rse, and tr y to p ut the ent ries in order , neatl y. Hut you will no t
be gr aded u pon the legib ility. neat ne ss, or order of your no teboo k. III fan , a note boo k that
is used in the laborato ry canno t be met icu lousl y clean and neat. O nly the en tr ies mad e wh ile
reading- o ther referen ces cou ld be ex pected to be re asonably neal. Be su re o f one th ing: o nl y:
that yon can u nd erstan d the en tri es in yo u r notebook. For example, la bel all n um bers
en tered in you r note book: a simp le " 2" m ight mea n two gr ams, two mi lli li ters, or two
anythi ng. O ne week after th is " 2" is wr itt en it ra n be awfu lly difficu lt to remem ber what it
mea nt a t the lime you wro te it.
The only way your notebook ca n affect yo ur grade adversely is if it d oes no t co nta in
yo u r na me; t he t itle o f the course: da tes 0 11 the t itle page and at the top of all pages from
page 4 on (where entr ies are found); a T able of Contents. filled in , consistent with the
materia l foun d on the fol lowing pages; and a b rief de..cript ivc t itle at th e top of each used
page . All o ther aspec ts arc up to you-it is yo ur notebook .
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