Determination Of Absolute Viscosity Using Ostwald Viscometer By Wenddie Aquien from The Handbook of Research on Virtual Workplaces and the New Nature of Business Practices. Practices . Eds. Kirk t. Amant and !a"el #emlansky. $ers%ey& !A' (dea )rou* !ublis%ing& +,,-.
Abstract: %e e/*eriment 0Determination of absolute "iscosity using Ostwald Viscometer1 was conducted to determine t%e absolute "iscosity of organic liquids& t%e relations%i* of "iscos "iscosity ity to tem*er tem*eratu ature re of sucros sucrosee soluti solution on and t%e unknown unknown concent concentrat ration ion of sucros sucrosee solution using Ostwald "iscometer. A definite "olume of liquid is *laced in t%e "iscometer& and t%e le"el of t%e liquid is drawn abo"e t%e to* mark of t%e bulb by suction. %e liquid is allowed to flow out freely& and t%e time& t& required for t%e le"el to dro* from t%e u**er mark to t%e lower mark is measured. West*%al West*%al balance is also used in t%is e/*eriment in measuring t%e density of t%e liquid. %e e/*eriment concluded t%at t%e "iscosity of a sim*le liquid decreases wit% t%e increasing tem*erature and "ice "ersa. As tem*erature increases& t%e a"erage s*eed of t%e molecules in a liquid increases and t%e amount of time t%ey s*end in contact wit% t%eir nearest neig%bors decreases. %us& as tem*erature increases& t%e a"erage intermolecular forces decrease.
Keywords' Viscosity& Ostwald Viscometer& West*%al Balance
I.
INTRODUCTION
%e internal friction in fluids& or "iscosity& "iscosity& is caused by t%e co%esion forces between molecules. 2olecules need energy en ergy to esca*e from eac% ot%er3s close interactions. Viscosity Viscosity is t%erefore a t%ermodynamic quantity& de*endent on tem*erature and *ressure. 4urt%ermore& "iscosity is a measure of t%e resistance of a fluid to being deformed by eit%er s%ear stress or e/tensional stress. (t is commonly *ercei"ed as 0t%ickness1& or resistance to flow. Viscosity describes a fluid3s internal resistance to flow and may be t%oug%t of as a measure of fluid friction. friction. %ere are actually two quantities quantities t%at are called "iscosity. "iscosity. %e quantity defined abo"e is sometimes sometimes called dynamic dynamic "iscosity "iscosity&& absolute absolute "iscosity "iscosity&& or sim*le sim*le "iscosity "iscosity to distinguis% it from t%e ot%er quantity& but is usually 5ust called "iscosity. %e ot%er quantity called kinematic "iscosity 6re*resented by t%e symbol 7 0nu18 is t%e ratio of t%e "iscosity of a fluid to its density 62ott& 9. :. +,,;8
Viscosity %as a unit of *oise in cgs w%ic% is named after t%e 4renc% *%ysician
?? 6=>?? @ =-;?8. =-;?8. !oise !oise is equi"al equi"alent ent to dynes dynesecon econd d *er square square centimeter. (t is t%e "iscosity of a fluid in w%ic% a tangential force of = dyne *er square centimeter maintains a difference in "elocity of = centimeter *er second between two *arallel *lanes = centimeter a*art.
= + $a"ing known t%e "iscosity of a liquid is im*ortant. %us& "iscosity *lays a "ital role to our daily li"es. (n t%e medical field for e/am*le& doctors always measures %ow "iscose t%e blood of %is *atient is. (t is because w%en a *atient3s blood b lood is too t%ick t%en it can cause clotting and lead to a %eart attack or stroke& or if it3s too t%in t%en %e can readily bleed from a small small cut for %ours. On t%e ot%er ot%er
%and& %and& in t%e %emica %emicall Engine Engineeri ering ng field& field& "iscos "iscosity ity
measurement also *lays a big *art in t%e industry. 4or e/am*le& w%en an engineer designs for t%e distribution system of water from a water *lant for a town& gi"en t%e a"erage demand of water for t%e town for any gi"en time& knowing t%e "iscosity of water& engineers will be able to know t%e flow of t%e water& t%e *ressure of t%e *i*es underground& t%e siCe of *i*es to be used& and more to follows.
(n t%e e/*eriment& t%e "iscosity of two liquids can be com*ared by making use of an Ostwald. %e liquids are allowed to flow t%roug% t%e ca*illary w%ile timed to determine e/*erimental "iscosity of eac% of t%e liquids being test. (n doing t%e e/*eriment& it is im*ortant t%at t%e students know before%and t%e basic *rinci*le t%at t%e density is t%e main factor t%at brings about t%e differences in t%e "iscosity of t%e different liquids. %us& density is directly *ro*ortional to t%e "iscosity& t%erefore& t%e smaller t%e density of a liquid& t%e smaller t%e smaller t%e "iscosity is& or "ice "ersa. Also& "iscosity "aries wit% tem*erature. (n general& t%e "iscosity of a sim*le liquid decreases wit% increasing tem*erature 6and "ice "ersa8. As tem*erature increases& t%e a"erage s*eed of t%e molecules in a liquid increases and t%e amount of time t%ey s*end 0in contact1 wit% t%eir nearest neig%bors decreases. %us& as tem*erature increases& t%e a"erage intermolecular forces decrease. %e e/act manner in w%ic% t%e two quantities "ary is nonlinear and c%anges suddenly w%en t%e liquid c%anges *%ase. Viscosity is normally inde*endent of *ressure& t%is do not "aries t%e "alue of "iscosity. ince liquids are normally incom*ressible& an increase in *ressure doesn3t really bring t%e molecules significantly closer toget%er. :astly& different fluids *ossess different amounts of "iscosity' syru* is more "iscous t%an water grease is more "iscous t%an t%e engine oil liquids in general are muc% more "iscous t%an gases. %e "iscosity of different fluids can be e/*ressed quantitati"ely by t%e coefficient of "iscosity& F 6t%e )reek lowercase letter eta8& w%ic% could be defined and calculated using t%e data t%at gat%ered in t%e following e/*eriment
G
Chapter 2 DESIGN AND METHODOLOGY
%e e/*eriment was *erformed using t%e Ostwald "iscometer . A clean Ostwald "iscometer was used in order to attain t%e acquired "alue for t%e e/*eriment. atmos*%eric
%e
*ressure was measured using t%e barometer and was essential to t%e data
acquired for t%e entirety of e/*eriment. %ermometer is used to measure t%e tem*erature of t%e liquid. A West*%al balance was used to measure t%e density of t%e water& benCene& c%loroform& met%anol and t%e unknown liquid. to*watc% was used in measuring t%e time t%at t%e liquid *ass t%roug% t%e reading mark in t%e "iscometer. ime& *ressure& density was found utiliCing t%e !ouiselle3s equation.
Before starting t%e e/*eriment& t%e re*orters followed t%e O! and guidelines for t%e laboratory 6wearing t%eir lab gowns& et al8.
to start t%e e/*eriment& a clean Ostwald
"iscometer was was%ed wit% %ydroc%loric acid followed by distilled water in order to was% all t%e remains of t%e ot%er liquid t%at stayed in t%e "iscometer. After t%e was%ing comes t%e drying. %e "iscometer is clam*ed "ertical using t%e clam* and t%e iron stand in order to read t%e "alue or t%e time ela*sed. Hml of water was *ut into t%e "iscometer in arm using t%e *i*ette until it is abo"e t%e mark at t%e to* of t%e bulb. !ut t%e rubber in t%e ot%er arm of t%e "iscometer in order to draw u*ward t%e water. Draw t%e water u* t%e ot%er arm of t%e tube until it is abo"e mark A. using t%e sto*watc%& time t%e water as t%e surface falls between mark A and B. 9e*eat twice more and take t%e a"erage reading of t%e t%ree as your mean time. After t%e t%ree trials for water& em*ty t%e "iscometer on t%e sink wit% *lenty of water. I H 9e*eat t%e *rocedure wit% benCene& c%loroform followed by met%anol t%en t%e unknown liquid. After t%e t%ree trials for c%loroform&
trials of t%e same number for
benCene &met%anol and unknown liquid were made. 9esults t%at followed were recorded. am*le com*utations were made and *assed after t%e +day of t%e designated E/*eriment .
Chapter 3 RESULTS AND DISCUSSION
%roug%out t%e course of t%e e/*eriment& t%ree trials were *erformed for eac% of t%e com*ounds 6water& benCene& c%loroform& met%anol and an unknown reagent8 for t%e determination of absolute "iscosity using t%e Ostwald "iscometer. %e Ostwald "iscometer was used to measure t%e "iscosity of eac% of t%e fluids in t%e e/*eriment. %e drag caused by t%e relati"e motion of t%e fluid and a surface is a measure of t%e "iscosity. %e flow conditions must %a"e a sufficiently small "alue of 9eynolds number for t%ere to be a laminar flow. Density is also *art of t%e equation of determining t%e "iscosity of t%e fluids& t%erefore t%e *erformers of t%e e/*eriment did t%ree trials for eac% of t%e reagents of t%e e/*eriment
using t%e West*%al
balance.
%e tem*erature at t%e gi"en density was also measured
because it is one of t%e factors in t%e density of t%e reagents. 4or t%e e/*erimentJs *rocess "ariable& "iscosity of a fluid is a measure of its resistance to gradual deformation by s%ear stress or tensile stress. 4or liquids& it corres*onds to t%e informal notion of t%ickness. %e results of all t%e trials for eac% of t%e c om*ounds were as follows' ?.II / =,LI wit% a *ercent error of ;.H?- / =,L *ercent error for water ??.H= *ercent error for benCene H.=-H *ercent error for c%loroform >+.,> *ercent error for met%anol -,.HI *ercent error for t%e unknown liquid. Wit% t%ese
data
acquired by t%e re*orters
earlier in t%e
e/*eriment&
"iscositycoefficient was sol"ed simultaneously using t%e equation' Ɲ M D / 6 nr N D / t8 A
; > sim*lified equation w%ere in DM density& nrM "iscosity coefficient& tM time in seconds (t is belie"ed t%at muc% of t%is error is caused by t%e misalignment of t%e Ostwald "iscometer. One degree of misalignment introduces = error. Anot%er source of error in t%e "iscometer is t%e requirement to use t%e e/act "olume of liquid for t%e reference liquid and t%e test liquid. %is requirement becomes furt%er *roblematic if t%e measurements are done at different tem*eratures. %e accurate knowledge of density is necessary to ad5st t%e colume at different test tem*eratures. 2ore error mig%t %a"e been caused by t%e u*rig%tness of t%e ironstand used in t%e e/*eriment.
Chapter 4 CONCLUSION AND RECOMMENDATION
%e determination of t%e rate of flow t%roug% a rigid ca*illary is t%e basis for an im*ortant met%od for t%e measurement of "iscosity. (n t%is met%od& t%e time of outflow of a known "olume of liquid t%roug% a ca*illary under t%e influence of gra"ity is determined. (n t%is e/*eriment& t%e re*orters concluded t%at t%e "iscosity of many liquids decreases as t%e tem*erature increases and "ice "ersa. %e "iscosity of a liquid also de*ends u*on t%e siCe& slo*e& and c%emical nature of t%e molecules w%ic% com*ose it. %emical forces between neig%boring molecules also influence "iscosity. And t%e "iscosity of a liquid increases& w%en it is sub5ected to increased *ressure. As t%e *ressure is increased& t%e molecules are crowded
more closely and t%ey %a"e less free s*ace left in w%ic% t%ey can mo"e. As t%e tem*erature is raised& t%e liquid e/*ands and t%e a"ailable free s*aced is increased. (n eac% case& t%e c%ange of "iscosity *arallels t%e free s*ace in w%ic% t%e molecules can *ass eac% ot%er. All of t%e "iscometer *arameters can be determined t%roug% careful measurement of t%e "iscometer dimension %owe"er& t%e "iscometer constant is generally determined by calibration using a fluid of known density and "iscosity. (t is well to em*%asiCe t%ose two absolute necessities for satisfactory "iscosity measurements are cleanliness of t%e "iscometer and an accurate tem*erature control. Ostwald "iscometer s%ould be cleansed t%oroug%ly before and after e"ery trial of t%e e/*eriment. ontamination may occur if t%e a**aratus was not cleansed and t%is may greatly affect t%e "alues of t%e "iscosity of t%e liquid sam*le. %e "iscometer must was% se"eral times by distilled water and be sure t%at it is totally dried b efore doing anot%er trial. ? %e "iscometer s%ould "ertically clam* to t%e iron stand. ilted "iscometer may affect t%e time s*ent of t%e liquid as well as t%e reading at w%ic% it *asses t%e calibration marks. %e re*orter w%o reads t%e liquid *asses t%e calibration marks s%ould be attenti"e in recording t%e time to a"oid errors.
AENDI! A Tab"es a#$ %&'(res COMOUND
TIME )s*
MEAN )s*
rial +
rial 2
rial 3
Water
=>.?? s
=-.+ s
=-.=; s
=-.=I s
BenCene
+>.I s
+>.?= s
+>.-I s
+>.> s
%loroform
. s
.=H s
.I, s
.+? s
2et%anol
.>= s
.> s
.H s
.;;> s
Unknown
I. s
I.> s
.-? s
I.=;->s
DENSITY )',-L*
TIME
MEAN DENSITY
rial + Water
rial 2
rial
= P +I deg. ,.???? P +.H elsius deg. elsius ,.->;H P +I ,.->II P +I deg. elsius deg. elsius =.I;?H P + =.I>, P +H deg. elsius deg. elsius ,.>? P +I ,.>? P +I deg. elsius deg. elsius ,.;H-; P +I ,.;H?H P +I deg. elsius deg. elsius ISCOSITY COE%%ICIENT ) Ɲ8
,.?; P + deg. elsius ,.Q->I? P + deg. elsius =.I;-? P + deg. elsius ,.>?I> P +I deg. elsius ,.;H?- P +I deg. elsius
rial +
rial 2
rial 3
Water
?.+? / =,L I
?.I> / =,LI
?.H?? / =,LI
?.II / =,LI
BenCene
=.+IHI / =,L
=.+;> / =,L
=.+? / =,L
=.+-=? / =,L
%loroform
+.H>; / =,L I
+.?;? / =,LI
+.>+? / =,LI
+.HHH- / =,LI
2et%anol
=.H+; / =,LI
=.H=?= / =,LI
=.H++- / =,LI
=.H++H / =,LI
Unknown
=.I;-; / =,LI
=.I?=H / =,LI
=.I,IH / =,LI
=.IHI? / =,LI
BenCene %loroform 2et%anol Unknown
,.?-;; P +.H deg. elsius ,.->; P +.H deg. elsius =.I?; P +.;> deg. elsius ,.>?-P +I deg. elsius ,.;H? P +I deg. elsius MEAN ) Ɲ8
able .= Data %eet for Water& BenCene& %loroform& 2et%anol and Unknown :iquid =, ++ &ct(res /0 Apparat(s (se$:
a8 Ostwald "iscometer Used to measure distance t%e liquid tra"els
b8 West*%al balance Used to measure t%e density of a liquid
c8 %ermometer Used to measure t%e tem*erature
d8 9eagent bottle w%ere liquids stored
e8 rubber tubing Used as a *assage for liquid or gas in e/*eriments
'* Ir/# sta#$ 1It s(pp/rts the -&t(re AENDI!
f8 *i*ette *um* Used to *um* air
h* c"a-p 1Use$ &# sec(r&#' the &sc/-eter
COMUTATIONS
=8 Water 6rial =8 ' ƝtM e/* 6= R +N R ln R I L H8 =M H+.-I +M >,.; M H.-;; IM H.->? / =,L+? Ɲt6true "alue8 M e/* S6H+.-I R 6>,.;N+IR+>.=H8 R H.-;; ln 6+I R +>.=H 8 R H.->? / =,L+? / 6+.H R +>.=H8L=, Q Ɲt 6true "alue8 M ?. I>> / =, LI !as
Ɲ=M e/* SH+.-I R 6>,.;N+I R +>.=H8 R H.-;; ln 6+I R +>.=H 8 R H.->? / =,L+? / 6+I R +>.=H8L=, Q Ɲ=M ?.+? / =,LI !as
2ean Ɲ=M 6?.+? / =,L I R ?.I> / =,LI R ?.H?? / =,L I8N M ?.II / =,LI !as
+8 BenCene 6rial =8 =M >.H=> +M +,?I.;M +.>?I IM , HM , Ɲt 6true "alue8 M e/* S>.H=> R +,?I.;-N+.HR+>.=H R +.>?I ln 6+.H R +>.=H8 R , 6 +.H R +>.=H8L, Q Ɲt 6true "alue8 M ,.+;? !a / s 6rue Value8 −4
ƝM D / 6 nr N Dr / t8 M
g 9.3293 x 10 Pa −s 0.8765 × 27.4 s [ ] mL 1g M =.+IHI /=,L !a / x 17.99 s ml
mean Ɲ+M 6=.+IHI / =,L R =.+;> / =,L R =.+? / =,L 8 N M =.+-=? /=,L !a /
=+ = 8 %loroform 6rial =8 =M =I.=,? +M =,I?.+ M ,.H>> IM , HM , Ɲt 6true "alue8 M e/* S=I.=,? R 6=,I?.+N +.;>R +>.=H8 R ,.H>> ln 6+.;> R+>.=H8 R , Q Ɲt 6true "alue8 M H.IH?I / =,LI
−4
ƝM D / 6 nr N Dr / t8 M
g 9.3293 x 10 Pa− s × 3.33 s [ ] 1.4695 mL 1g M +.H>; /=,L I !as x 17.99 s ml
mean Ɲ M 6+.H>; / =,LI R +.?;? /=,LI R +.>+? / =,LI8 NM +.HHH- /=,LI !as
I8 2et%anol 6rial =8 = M +H.=> +M =>-?.+ M +.,;? IM , HM , Ɲt 6true "alue8 M e/* S+H.=> R 6=>-?.+N +IR +>.=H8 R +.,;? ln 6+IR+>.=H8 R , Q
TtM H.IH=; / =, LI !a 6true "alue8 −4
ƝM D / 6 nr N Dr / t8 M
g 9.3293 x 10 Pa− s × 3.71 s [ ] 0.7933 mL 1g M =.H+; /=,L I !as x 17.99 s ml
mean ƝM 6=.H+; / =,LI R =.H=?= /=,LI R =.H++, / =,LI8 N M =.H++H /=,LI !as
H8 Unknown 6rial =8 −4
0.6586
ƝM D / 6 nr N Dr / t8 M
g 9.3293 x 10 Pa−s × 4.3 s [ ] mL 1g M =.I;-; /=,L I !as x 17.99 s ml
=M ;.H;=I +M HI+.+ M .;I IM -.,I-> /=,L> HM =+.-I Ɲt 6true "alue for unknown8 M e/* S;.H;= R 6HI+.+N6+IR+>.=H88 R.;I ln 6+IR+>.=H8 R -.,I-> /=,L> 6+IR +>.=H8L=+.-I Q =I Ɲt 6true "alue for unknown8 M >.HIH, / =,L !as
!E9ET E99O9 =8 $+,
errorM S6?.I? / =,L I ?.I /=,LI8 N ?.I> / =,LIQ / =,, M ;.;,+ / =,L=, +8 BenCene errorM S6,.+;? =.+-=? / =,L8 N ,.+;?Q / =,, M ??.H=I+ 8 %loroform error M S6H.IH?I / =,L I +.HHH- /=,LI8 N H.IH?I / =,LIQ / =,, M H.=-H I8 2et%anol error M S6H.IH=; / =,L I =.H++H /=,LI8 N H.IH=; / =,LIQ / =,, M >+.,>+I H8 Unknown errorM S6>.HIH, / =,L =.I;-; /=,L I !as8 N >.HIH, / =,L Q / =,, M -,.HHI
AENDI! C A$$&t&/#a" r/b"e-s
=
(n an e/*eriment wit% an Ostwald "iscometer& t%e times of flow of water and et%anol are -,s and =>Hs at +,. %e density of water is ,.??-gNcm and t%at of et%anol
,.>?, gNcm. %e "iscosity of water at +, is ,.,=,,- *oise. alculate t%e "iscosity of et%a%ol. )i"en' T=20°C
t water M -,s t et%anol M =>Hs ρwater M ,.??-
ρet%anol M ,.>?,
g cm ³ g cm ³
F 6water8 M ,.,=,,- *oise
9equired' F 6et%anol8
olution' g cm.s F 6water8 M ,.,=,,- *oise 6 8 M ,.,=,,1 poise 1
g cm.s
ηr η (ethanol) = ( ρ ethanol)(t ethanol)( ρrtr ) 0.01008 g
η (ethanol) = (0.790
g cm ³ )(175s)(
η (ethanol) = 0.0175
g cm.s
cm.s ) 0.998 g ( 80 s ) cm ³
15
+
=; An e/*eriment was *erformed t%at measured t%e flow of four different liquids as tem*erature was increased. According to t%e gra*%& w%ic% of t%e liquids %ad t%e greatest "iscosity at a tem*erature of ,
+ , E2!E9AU9E 68 ,
=,
+,
,
:egend' A B D
Answer' %e liquid t%at %as t%e greatest "iscosity at tem*erature , is :iquid D.
%e dimensional formula of coefficient of "iscosity is XXXXXX Answer' ηr η = (ρ)(t )( ρr tr )
I
$ow does t%e "iscosity of a liquid c%ange wit% tem*erature
=> Answer' Viscosity of a liquid c%ange wit% tem*erature in a way t%at "iscosity decreases as is tem*erature increases.
H
(n an e/*eriment wit% an Ostwald Viscometer& t%e "iscosity of t%e toluene and water at , is ,.H>? and ,.-,,> *oise. %e times of flow of water and toluene are I=s and I.Hs. %e density of water is =.,,+ gNcm. alculate t%e density of toluene. )i"en' M, t water M I=s t toluene M I.Hs ρwater M =.,,+
g cm ³
F 6water8 M ,.-,,> *oise F 6toluene8 M ,.H>? *oise 9equired' ρtoluene
olution' g cm.s F water M ,.-,,> *oise 6 8 M ,.-,,> 1 poise 1
g cm.s F toluene M ,.H>? *oise 6 8 M ,.H>? 1 poise 1
ηr F toluene M 6 ρtoluene86t toluene86 ρr tr 8
g cm.s g cm.s
0.8007
,.H>?
g cm.s M 6 ρtoluene86I.Hs86
1.002
g cm.s
g cm
(41 s )
8
3
g
ρtoluene M ,.-;==
cm
3
RE%ERENCES
Books' Atkins& !eter W. and de !aula&
Atkins& !eter W. and de !aula&
=-
