Chapter 4 HEAT4.3 Gas Laws4.3 Gas LawsLearning outcomesexplain
gas pressure, temperature and volume in terms of the behaviour of
gas moleculesdetermine the relationship between pressure and volume
at constant temperature for a fxed mass of gas i.e. pV
constantdetermine the relationship between volume and temperature
at constant pressure for a fxed mass of gas i.e. V/Tconstant4.3 Gas
LawsLearning outcomesdetermine the relationship between pressure
and temperature at constant volume for a fxed mass of gas i.e. P/T
constantexplain absolute !eroexplain the absolute"#elvin scale of
temperaturesolve problems involving pressure, temperature and
volume of a fxed mass of gasThe Idea of Gas Laws4.3 Gas LawsThe
Idea of Gas Laws4.3 Gas LawsThe observation of the events show that
a gas has VOLUME (V) and TEMPERATURE (T) and it exerts a PRESSURE
(P).The Idea of Gas Laws4.3 Gas LawsProperty and symboS! base "n#t
Ot$er Un#ts$ressure, P% cm&', cm Hg(olume, V mm),
cm)Temperature, ToC*g m&+ s&'m)#The Idea of Gas Laws4.3 Gas
LawsRelationship between P and V (Constant T)4.3 Gas Laws,hen the
volume of a gas is decreased, the number of molecules remains
unchanged.4.3 Gas LawsThe same number of molecules moves in a
smaller space.Relationship between P and V (Constant T)4.3 Gas
LawsThe molecules collide more with the walls of the container.
frequentlyRelationship between P and V (Constant T)4.3 Gas
LawsHence, the pressure exerted b- the gas isgreaterRelationship
between P and V (Constant T)4.3 Gas LawsVP1Relationship between P
and V (Constant T)4.3 Gas Laws,hen a gas is heated, the average
*inetic energ- of the particles of gas increasesRelationship
between P and T (Constant V)4.3 Gas LawsHence, the gas molecules
stri*e the walls of the container at a higher fre.uenc- and more
vigorousl-.Relationship between P and T (Constant V)4.3 Gas
LawsTherefore, the pressure of the gas increases.Relationship
between P and T (Constant V)4.3 Gas LawsT P Relationship between P
and T (Constant V)4.3 Gas Laws,hen a gas is heated, the average
*inetic energ- of the particles of gas increases.Relationship
between V and T (Constant P)4.3 Gas LawsHence, the gas molecules
stri*e the walls of the container at a higher fre.uenc- and more
vigorousl-.Relationship between V and T (Constant P)4.3 Gas Laws/f
the gas is allowed to expand, the faster molecules now move in a
bigger space. Relationship between V and T (Constant P)4.3 Gas
LawsTherefore, the rate of collision between the molecules and the
walls remain constant and thus the pressure is constant. the gas is
allowed to expand, the faster molecules now move in a bigger space.
Relationship between V and T (Constant P)4.3 Gas LawsT V
Relationship between V and T (Constant P)4.3 Gas LawsRelationship
between V and T (Constant P)Relationship between P and T (Constant
V)Relationship between P and V (Constant T)%oye&s LawPress"re
Law'$ares& LawVP1T P T V 4.3 Gas Laws%oye&s LawBoyles law
states that the press"re of a fxed mass of gas is #n(ersey
proport#ona to its (o"me provided the temperature of the gas is
*ept constant.constant1= PV orVP4.3 Gas Laws%oye&s
Law+initial'fnal2 2 1 1V P V P =4.3 Gas Laws4.3 Gas Laws%oye&s
Law)rap$s4.3 Gas LawsPress"re LawBoyles law states that the
press"re of a fxed mass of gas is d#re*ty proport#ona to its
absolute temperat"re 0in #elvin1 provided the volume of the gas is
*ept constant.constantT= PorT P4.3 Gas LawsPress"re Law2211
TPTP=+initial'fnal2T in #elvin 0#14.3 Gas LawsPress"re Law)rap$sThe
temperature &'3) oC is the lowest possible temperature.4.3 Gas
LawsAbso"te temperat"reThe graph intersects at &'3) oC.This
temperature is called abso"te +ero.The temperature &'3) oC is
the lowest temperature theoreticall- achievable.4 #&'3) oC 4.3
Gas LawsAbso"te Temperat"reTo convert from the Celsius scale into
the absolute temperature, -ou add '3).+5 and change 6C to #. To get
a temperature on the absolute scale to the Celsius scale, subtract
'3).+5 and change # to 6C.( )Celcius inre temperatuKelvin ine
temperaturK 273==+ =TT4.3 Gas LawsAbso"te Temperat"re4.3 Gas
LawsThe corresponding temperatures in the Celsius and #elvin scale
are as follows7 4.3 Gas Laws'$ares& LawCharles law states that
the (o"me of a fxed mass of gas is d#re*ty proport#ona to its
absolute temperat"re 0in #elvin1 provided the pressure of the gas
is *ept constant.constantT= VorT V4.3 Gas Laws'$ares& Law2211
TVTV=+initial'fnal2T in #elvin 0#14.3 Gas Laws'$ares&
Law)rap$sThe temperature &'3) oC is the lowest possible
temperature.4.3 Gas Laws%oye&s LawPress"re Law'$ares&
Law4.3 Gas LawsEample ! " #o$le%s LawAn air bubble of capacit- +5
cm) at a pressure of )'4 cm Hg is released from the sea. 8etermine
the volume of the bubble when it reaches the surface of the water,
if the atmospheric pressure is 39 cm Hg. Assume that the
temperature of the water is constant. 4.3 Gas LawsEample ! "
#o$le%s Law4.3 Gas LawsEample & " Pressure LawAn iron c-linder
containing gas has a pressure of )94 *$a when it is *ept in a store
at temperature '3 4C. ,hat is the pressure of the gas when the
c-linder is moved outdoors where the temperature is 44 4C. 4.3 Gas
LawsEample & " Pressure Law4.3 Gas LawsEample ' " Charles LawA
s-ringe in a refrigerator contains 4.5 ml of air at &)4C. ,hen
the s-ringe was ta*en out and placed in a room where the
temperature was '34C, the air in it expands. Calculate the fnal
volume of the air in the s-ringe. 4.3 Gas LawsEample ' " Charles
Law4.3 Gas Laws#$ combining the laws( we obtain%oye&s
LawPress"re Law'$ares& LawVP1T P T V GE,ERAL GAS LA-22 211 1TV
PTV PT PV=
