States of Matter_gas

8/18/2019 States of Matter_gas

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States of

Matter


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States of MatterMatter can mainly beclassied in three ways:

1.Classical States of matter2.Non classical states ofmatter

3.States classied accordingto the energy content in them.


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3


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Phase changes of matter

Solid Li!id

"as

Plasma

Melting

#ree$ing

%e&osition

S!blimation

'a&ori$ationCondensati

on

%eioni$ation

(oni$atio

n


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5

Gases

Properties of Gases

Gas Pressure


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11

Kinetic Molecular Theory of Gases

A gas consists of small particles that:

Move rapidly in straight lines

Have essentially no attractive (or

repulsive) forces Are very far apart

Have very small volumes compared

to the volume of the container they

occupy Have kinetic energies that increase

with an increase in temperature


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12

Properties of Gases

• Gases are described in terms of four properties:

pressure ()! volume (")! temperature (#)! and

amount (n)$


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13

Gas pressure:

• %s described as a force acting on a specific area

ressure () & 'orce

Area• Has units of atm! mm Hg! torr! and pascals

• atmosphere ( atm) is *+ mm Hg

• mm Hg & torr

$++ atm & *+ mm Hg & *+ torr

Gas Pressure


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Origin of Pressure


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15

Units of Pressure

Gas pressure!

• %s described as a force acting on a specific area


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16

A$ ,hat is -. mm Hg e/pressed in atm0

) -. atm

1) +$*1. atm

2) 2$* / +. atm

3$ #he pressure in a tire is 1$++ atm$ ,hat is thispressure in mm Hg0

) 1$++ mm Hg

1) .1+ mm Hg 2) 11 2++ mm Hg

Learning Check


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17

A$ ,hat is -. mm Hg e/pressed in atm0

1) +$*1. atm

-. mm Hg / atm & +$*1. atm

*+ mm Hg3$ #he pressure of a tire is measured as 1$++ atm$ ,hat is

this pressure in mm Hg0

1) .1+ mm Hg

1$++ atm / *+ mm Hg & .1+ mm Hg atm

Solution


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18

Atmospheric Pressure

#he atmospheric pressure:

• %s the pressure e/erted

by a column of air from

the top of the

atmosphere to the

surface of 4arth

• %s about atmosphere

or a little less at sea

level


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19

Altitude and Atmospheric Pressure

Atmospheric pressure:

• 5epends on the

altitude and the

weather

• %s lower at high

altitudes where the

density of air is less

• %s higher on a rainy

day than on a sunny

day


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20

arometer

A barometer:

• Measures the pressure

e/erted by the gases

in the atmosphere

• %ndicates atmospheric

pressure as the height

in mm of the mercury

column


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21

A$ #he downward pressure of the Hg in a barometer is 66666 than (as) the pressure of the atmosphere$

) greater 1) less 2) the same

3$ A water barometer is 2$* times taller than a Hgbarometer (5Hg & 2$* g7m8) because:

) H19 is less dense

1) H19 is heavier

2) air is more dense than H19

Learning Check


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22

A$#he downward pressure of the Hg in a barometer is

2) the same (as) the pressure of the atmosphere$

3$ A water barometer is 2$* times taller than a Hgbarometer (5Hg & 2$* g7m8) because:

) H19 is less dense

Solution


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)tmos&heric Press!re

)tmos&heric &ress!re is theforce &er !nit area e*erted into as!rface by the weight of air

abo+e that s!rface.)tmos&heric &ress!re is calc!lated in +ario!s!nits. ,he following e!i+alence is the mostcommonly !sed.

1 atm- 11/0 Pa- / mmg-/ torr)tmos&heric &ress!re can sim&ly be meas!redby a barometer by balancing the weight of


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,em&erat!re(t is a meas!re of the thermalenergy of molec!les or atoms of as!bstance.

,em&erat!re too has many !nits as&ress!re.

,he relationshi& between these

scales can be s!mmari$ed asfollows:

4#- 567084C 9 32

- 4 C 9 23


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"as Laws ,here are si* main gas lawsassociated with the beha+ior ofgases:

1. Law3.Charles?"ay?L!ssac=s law

@.Combined "as Law0.)+ogadro>s law.%alton=s law of &artial &ress!re


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THE GASLAWS


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BOYLE’S LAWThe inverse relationshipbetween pressure and volume

It states that the volume o asample o !as "han!esinversel# with the pressure o

the !as as lon! as thetemperature and the amounto the !as remain "onstant$


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Bhen the &ress!re of the

gas decreases the +ol!meof the gas increases.

Bhen the &ress!re of a gasincreases the +ol!me of thegas decreases.

%&'& ( %)')


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SA*%LE %+OBLE*S,

1. ) tanD of nitrogen has a+ol!me of 1@./ L and a

&ress!re of /./ mmg.#ind the +ol!me of thenitrogen when its &ress!re is

changed to @//./ mmgwhile the tem&erat!re is

held constant.


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2. ) 2//?L heli!m gas at a

&ress!re of 2E/C and a&ress!re of 2./ atm wastransferred to a tanD with a+ol!me of E./ L. Bhat isthe internal &ress!re of the

tanD if the tem&erat!re ismaintainedF


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3. ) balloon contains 1@./ L of

air at a &ress!re of / torr.Bhat will the +ol!me of theair be when the balloon istaDen to a de&th of 1/ ft in aswimming &ool where the

&ress!re is 6E1 torrF ,hetem&erat!re of the air doesnot change.


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C)ALGS= L)BStates that the el+in tem&erat!reand the +ol!me of a gas are directlyrelated when there is no change in&ress!re or amo!nt of gas.

,he relationshi& between +ol!me

and tem&erat!re was rst obser+edby #rench &hysicist and balloonist Hac!es Charles.


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Charles> Law

)&&licable only if: Press!re staysconstant

)&&licable to:1.(deal gases at any tem&erat!re

2.Aeal gases which beha+e

a&&ro*imately as ideal gasess&ecially at low &ress!res.


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2

2

1

1

T

V

T

V =

2

2

1

1

T

V

T

V =


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S)MPLG PAI


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2. #ind the naltem&erat!re of a 2.//?L gas sam&le at 2/.//Ccooled !ntil it occ!&iesa +ol!me of 0// mL.


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%o the J. e*ercises:

1. ) sam&le of #reon gas !sedin air conditioner has a +ol!me

of 320./ L and a &ress!re of6.3 DPa at 2//C. Bhat will the&ress!re of the gas be whenits +ol!me is 60./ L at 2//CF


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2. ) balloon contains 3/./Lof heli!m gas at 1// DPa.Bhat is the +ol!me when

the balloon rises to analtit!de where the

&ress!re is only 20./ DPaF


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3. Bhat is the +ol!me ofa sam&le of ethane at

@ and 2.20 atm if itocc!&ies 1.@/0 L at

3// and 2.20 atmF


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")K?LSS)C=S L)B ,em&erat!re and&ress!re relationshi&

,he &ress!re of a gasis directly related to

its el+in tem&erat!re.


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This means that an in"rease

in temperature in"reasesthe pressure o a !as- and ade"rease in temperature

de"reases the pressure othe !as as lon! as the

volume and number omoles o the !as remain"onstant$


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"ay?L!ssac=s Law: Aelating&ress!re and tem&erat!re


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2

2

1

1

V

n

V

n=

2

2

1

1

T

P

T

P =


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S)MPLG PAI


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2$ The pressure in

automobile tire is ).. /%aat a temperature o )0.1$At the end o a 5ourne# on

a hot sunn# da#- thepressure has risen to ))6/%a$ What is thetemperature o the air inthe tire4


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)'I")%AI=S L)BLaw: G!al +ol!mes of gases at thesame tem&erat!re and same &ress!recontain the same no. of molec!les 7

atoms.Modied law: G!al +ol!mes of gasesat the same tem&erat!re and same

&ress!re contain the same no. ofmoles.

5Since no. of moles- no. of atoms ormolec!les )+ogadro N!mber8


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2

2

1

1

n

V

n

V =

S)MPLG PAI


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S)MPLG PAI


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9etermine the

volume in literso""upied b# .$).)

mol o a !as at ST%$How man# o7#!en

mole"ules are in 6$6liters o o7#!en !asat ST%4

9 i h


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9etermine the

volume in literso""upied b# &:$. !o ;) at ST%$

What volume iso""upied b# :$.) 7&.)) mole"ules o ))! o H) at ST%4


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,G CIM


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Combined "as Law

P' ,

D

Bhen P ismaintainedconstant'7, - D. ,herefore

the system obeys=

Bhen , ismaintainedconstant P' -D. ,herefore the

system obeysthe


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S)MPLG PAI


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2. ) 0./ L air sam&le at a

tem&erat!re of 0/.//C hasa &ress!re of 1/./ DPa.

Bhat will the new &ress!rebe if the tem&erat!re israised to 1//.//C and the

+ol!me e*&ands to ./ LF


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3. ) 3.0/?L gas sam&le at2//C and a &ress!re of E.

DPa is allowed to e*&and toa +ol!me of E./ L. ,he nal&ress!re of the gas is 0.

DPa. Bhat is the naltem&erat!re of the gasF


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,G (%G)L ")S L)B

,he law that describes

the &ress!re +ol!metem&erat!re andn!mber of moles of agas.


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%'( n+T

Where,%( pressure o the !as

'( volume o the !asn( amount o !as

+( ideal !as "onstant

T( temperature o the!as


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At ST%-

P- 1./ atm- 1/1.320 DPa'- 22.@ L

n- 1./ mole ,- 23

A- /./E21 atm * L7 mol * - E.31DPa * L7 mol *


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S)MPLG PAI


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2. ow many moles ofgas are contained in a0/./?L cylinder at a

&ress!re of 1//./ atmand a tem&erat!re of

30.//CF


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3. Bhat &ress!re will bee*erted by /.@0/ mol

of a gas at 20/C if it iscontained in a +essel

whose +ol!me is /.0LF


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) th f ll i


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)nswer the followinge*ercises:

1. ) dee& !ndergro!nd ca+erncontains 2.2@ * 1/ L of

methane gas5C@8 at a&ress!re of 10// DPa and atem&erat!re @2/C. ow many

Dg of methane does this gasde&osit containF


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2. ,he +ol!me of a gas?lled balloon is 3/./ L

at @/.//C and 10/ DPa&ress!re. Bhat +ol!me

will the balloon ha+e atS,PF


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@. Bhen a rigid hollow

s&here containing E/ Lof heli!m gas is heated

from 3// to // the&ress!re of the gasincreases to 1 E// DPa.

ow many moles ofheli!m are in the s&hereF


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0. ) container with an initial

+ol!me of 1./ L is occ!&iedby a gas at a &ress!re of 10/DPa at 20/C.


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S!mmary

(deal gase!ationP' -nA,

"as law&roblems

Combinedgas e!ation

5P'87, - D

Charles?"ayL!ssac=s law

P7, - D

Charles=slaw

'7, - D


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9ALTO;’S LAW

At "onstant volume andtemperature- the total

pressure e7erted b# ami7ture o !ases ise


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Ptotal-

P19P29P3

S)MPLG PAI


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S)MPLG PAI


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A balloon "ontains mostl# Heand a little methane$ The

partial pressure o helium is&.&$) /%a$ I the pressureinside the balloon is &.&$6/%a- what is the partialpressure o methane4


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A 8$06> L ?as/ at )8.1"ontains .$.6@@ mol o

;)- .$& :0 mol o 1O- [email protected] mol o H)$ Whatis the pressure in the

?as/ in atm and /%a4

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States of Matter_gas