CBSE Class 11 > Class 11 Videos > L4 : State & path function - Thermodynamics, Class 11
L4 State & path function - Thermodynamics, Class 11 Video Lecture
FAQs on L4 : State & path function - Thermodynamics, Class 11
| 1. What is a state function in thermodynamics? |  |
Ans. A state function in thermodynamics is a property that depends only on the current state of a system and not on how the system reached that state. Examples of state functions include temperature, pressure, volume, and internal energy.
| 2. What is a path function in thermodynamics? | |
Ans. A path function in thermodynamics is a property that depends on the path taken to reach a particular state. It is not dependent on the initial and final states of the system. Examples of path functions include work and heat.
| 3. How is work related to path function? | |
Ans. Work is a path function in thermodynamics, which means that it depends on the path taken to achieve a certain change in a system. The work done on or by a system can be different depending on the specific path chosen to reach the final state. The formula for work, W, is given by the integral of the pressure, P, with respect to volume, V, over the chosen path: W = ∫PdV.
| 4. Can you give an example of a state function and a path function? | |
Ans. Temperature is an example of a state function because it only depends on the current state of a system, regardless of how the system reached that state. On the other hand, work is an example of a path function because it depends on the specific path taken to achieve a certain change in the system.
| 5. Why are state functions important in thermodynamics? | |
Ans. State functions are important in thermodynamics because they simplify the analysis and calculation of thermodynamic processes. Since state functions only depend on the current state of the system, they can be easily measured or determined. Additionally, the change in a state function between two states is independent of the path taken, making it easier to analyze and compare different thermodynamic processes.
Text Transcript from Video
hello friends this video on
thermodynamics parkour is brought you by
exam fear calm no more fear from exam
before watching the video please make
sure that you have washed part 1 - Part
3 don't that come on our eyes we deal
with only with the initials in - state
and that's why we have something of
state function path function let's let's
define state and the path function so
state function is something whose value
depends only on the state of the
substance not on how it is reached so
example was volume pair if you see the
river I take one river example have
norton from the picture this forever and
this water do I care from where the
water has come where it has come from
tributary one tributary to tributary
three or some drainage factory or some
drain from the home I don't care I just
care about the volume of the water that
river has correct so the path from where
DZ the water has come I don't care
so thus if you see the volume is
generally state function I don't care
how the volume King right or in the
flask oh so if you are doing the
experiment for example if you're doing
if you're doing is an experiment flask
and you need let suppose let us do 40 ml
of water for teaming up so do you care
whether this 40 ml this 40 ml has come
from tap one tap 2 or you pour this
using test tube or you pour this your
reason flask you here you don't care you
just care about a 40 ml of water if you
have 40 ml of water that's all for you
you don't care from where you've got
this may or 10 ml you you got from the
water 10 ml you what do you put for the
test tube 10 ml you take from our tube
from your friend 10 ml you to 40 he
won't care you will live here but the
part even awarding correct so such kind
of thing where you just give it a fine
modulation state you don't care how you
cut it that is state function heroes if
you see TV example they are kinder than
1
home and they are both starting from
this point so this is a single point
they're starting so you know what we
don't care actually if you don't care
the use more generation whether it's see
when this path this path of this time
you don't care but if you talk about
things like how much energy is spent in
reaching from point A to this home for
this girl that will differ based on the
path so if this example if she takes
this path so if you take this bar she'll
have to cover more distance so the work
done for this girl from moving point A
to point is different in all this path
because if she walk more she will need
more see that we see has n more work so
such thing example word will not be a
state version that will be path function
because that is depend on the path path
you take correct
so path function is something which is
dependent on the path you take example
here the work work is a path function
correct because from here to here if she
is going she is doing different amount
of work right if she is or if she is a
let's suppose I mean you just see the
four different paths you know and all
these different paths still have no
different amount of work you reach this
phone so the work done will be a path
function that depends on the project
correct so let's take some example for
the state and path function is volumes
Tito path function yes it is a state
function we have seen that if you are
doing a experiment
in the lab you just care about a volume
of let's suppose water or any acid
require I don't care how you got this
you get from bigger one we can do
because three till you using test-tube
you don't care
temperature yes it is a stake much why
for example same case as opposed no you
have this beaker and you want to
maintain eg Celsius for some experiment
do you care if you are getting use 80
degree Celsius from a Bunsen burner
burner here or you are putting some
immersion rod here or you got this hot
water from a user and you are using it
or you using firewood do you hear you
don't hear you don't care how this
evening this as this temperature came
whether it was a hot water from a geezer
with a Bunsen burner that I was little
but the drink is bad
oh it was a volt fire or it was a heater
you don't care or whether did you use a
microwave oven if it this one you don't
care you only care about the LEDs this
is temperature so it is also state
forest pressure
same thing with the pressure you don't
care how you got this pressure to doing
some experiment you want some let's
suppose five atmospheric pressure you
don't care how you got this whether you
need some chemical reaction to get this
pressure whether you example in this
case you you have put some iron here and
you squeeze the volume to get the
pressure or you are pressuring with your
hand you don't care or you need some
hydraulic device you don't care you only
care about let's suppose five
atmospheric pressure that's all you care
you don't care how you got this pressure
so pressure will also be a state
function
density density loss of a state but you
don't care how you got a density example
you had this water you had milk actually
had milk with some density and you want
to make it a little thicker
exactly 1 st 1 and you wanted to make it
nice to do it do thicker it will think
of more dense more dense you want make
it do you care whether if you are using
microwave oven to heat this up and
reduce density or you're using some gas
LPG gas or you are using wood do you
hear you don't hear just care about
different densities you don't care how
you got this right whether you use
microwave oh man you used it here maybe
heater to heat this boil this and review
density or did you use a LPG gas and the
gas stove and estaba or did you use a
wood you don't hear how you got this you
only care what density so it is also
stable same thing with the mass example
I want 10 kg of iron do I care if I got
this 10 kg from 10 different people each
1 kg each and I got 10 G's or do I care
if I got 2 kg 1 3 people and Fergie from
1 and I got 10 kg total or do I hear the
vigor got 10 the whole thing from my
teacher I don't care from where I got
how I got the same kg do I care if I
have put a glazing on that one I don't
hear I asked about 10 kg so it is also
state function interrelating do I care
how the Internet is G seen I don't care
I just care about the Internet in the
current internal energy of the system I
don't care how it is achieved the
internal energy also is a stable heat
his heat a stateful
this is tricky one he is not a state
nation he is a path function
see we did talk about heat we talk about
heat flow or heat transfer correct so it
suppose I take my system and I can't say
the heat is this much this you can't see
heat is applied only well let's suppose
there is a hot object and there is a
cold object when they are in touch the
heat flows from hot to cold and once
they are in equilibrium the heat doesn't
flow it
so heat flow doesn't happen always it
happens only to wreak a process where
the two objects are in different
temperature correct so I can't say that
heat is a state function that I can't
see for sure because example I have some
flasks with some water just with this
flask this and water I can tell that the
volume of this water is this small in
the state I can tell the temperature of
this water is this some Celsius so
temperature state function
I can tell the pressure here is this I
can tell the pressure also some X
atmospheric pressure I can't invest your
body so the density is also state
function I can tell the mass of what was
a mass is also stable or this I can tell
they internalized your internal GOCC
but heat I can't tell heat comes only
when this water is in touch with some
hot object a cold object and then
transfer of heat thickness right so heat
is nothing but heat flow so it is not
the state function it is not the state
correct we talk about work work is also
known as statements example I showed you
example this is one right here I have to
reach this destination
I can take this path do more work in
this this path are blue less one
similarly the next example I can take is
the length length is also not a state I
am saying that I am have to go from
point A to my point B so the length is
different if I take path 1 and if I take
part well it'll be different right all
right Nick passing length
so length is also not a state function
so if you see he'd work and length are
not a state function their path function
other things are generally state fish
also for state fertility just tell that
this is the correct
so heat and work is not a state please
note that he did work in order but the
trick part is internal energy you see it
will drag this law is nothing but heat
plus work
these two are not state function but
internal energy change is a state
function this is something it is strange
right and a good example to explain this
is for example I have to expand some gas
so from this volume I have to expand to
this one and making sure that this have
that opposed pressure per one and volume
v1 this guy also has a pressure it
expands they should even work so one we
can be if you want to maintain the
temperature if it expands since you are
keeping these constant we have this PV
is equal to NRT the ask equation we have
to supply some temperature some heat
some heat P a root of life or you want
we can expand adiabatically also where
we don't have to supply the heat and
expand in that case they'll be work done
by the system give me some volume my
system so if you see in both case the
energy change is same either this way
this is my gas I have to expand to this
this much volume right both has gas
there are two paths one option I am
saying is you read this another item
saying the work is done by system
idiotically in both case in internal
energy c barred if you see the path is
different so you see this Q and W both
are path function
the change in internal energy is a state
function we'll discuss more on these let
me take some examples similarly we
talked about a state we take an example
of a card just in case you're a little
bit confused with the thumb and I swore
let's take the car you talked about car
we talked about things like what is the
location of the sky where does point a
one point B what is the orientation
whether it's pointing with this fire or
pointing this side East Side west side
what is the speed of the car
all these are stage of the car correct
because with that C at a given point we
can tell the location orientation speed
so these are the states these are the
states which defined the state of the
car the point e supplied in Simon is
word when I say this is a flask it has
water I can say that how much volume of
water it has what is the temperature it
has what is the designate has what is
the pressure it has what is the mass of
the water it has all these are my state
function in the thermodynamics what so
similar to car we have states of the
system so they told pressure volume
temperature and the composition of the
system that is the mass of the system
example is my flask it has some water
so all these pressure volume temperature
the mass density all these things are my
state of the system the chemical system
to be more specific
and these are my state systems same as I
told state variables and other things
which depends only the state and my
examples are pressure volume temperature
internal energy mass density and we
define the chemical system by the state
variables not by the path alright so as
I told my thermodynamic system example
that we have a gas you can define the
seat of the gas by telling its pressure
volume temperature the number of moles
ejected
so those things those parameters will be
using more often to solve various
numerical
Dominic's sister and these videos
pressure volume temperature number of
moles all these are mines chain bales
correct and please note to define AG
state a system we don't define all even
if we know pressure of all living in
find temperature because we have this
gas laws so if you know some parameter
or if you know some state variable you
can very well find other signal even
also so you don't need to define all the
properties even if you have some
properties some state variables you can
find the other ones thank you visit exam
viacom to watch free educational videos
try free online tests get the best
quality study materials study from the
best tutors and mentors and much more
thanks and serene
thermodynamics parkour is brought you by
exam fear calm no more fear from exam
before watching the video please make
sure that you have washed part 1 - Part
3 don't that come on our eyes we deal
with only with the initials in - state
and that's why we have something of
state function path function let's let's
define state and the path function so
state function is something whose value
depends only on the state of the
substance not on how it is reached so
example was volume pair if you see the
river I take one river example have
norton from the picture this forever and
this water do I care from where the
water has come where it has come from
tributary one tributary to tributary
three or some drainage factory or some
drain from the home I don't care I just
care about the volume of the water that
river has correct so the path from where
DZ the water has come I don't care
so thus if you see the volume is
generally state function I don't care
how the volume King right or in the
flask oh so if you are doing the
experiment for example if you're doing
if you're doing is an experiment flask
and you need let suppose let us do 40 ml
of water for teaming up so do you care
whether this 40 ml this 40 ml has come
from tap one tap 2 or you pour this
using test tube or you pour this your
reason flask you here you don't care you
just care about a 40 ml of water if you
have 40 ml of water that's all for you
you don't care from where you've got
this may or 10 ml you you got from the
water 10 ml you what do you put for the
test tube 10 ml you take from our tube
from your friend 10 ml you to 40 he
won't care you will live here but the
part even awarding correct so such kind
of thing where you just give it a fine
modulation state you don't care how you
cut it that is state function heroes if
you see TV example they are kinder than
1
home and they are both starting from
this point so this is a single point
they're starting so you know what we
don't care actually if you don't care
the use more generation whether it's see
when this path this path of this time
you don't care but if you talk about
things like how much energy is spent in
reaching from point A to this home for
this girl that will differ based on the
path so if this example if she takes
this path so if you take this bar she'll
have to cover more distance so the work
done for this girl from moving point A
to point is different in all this path
because if she walk more she will need
more see that we see has n more work so
such thing example word will not be a
state version that will be path function
because that is depend on the path path
you take correct
so path function is something which is
dependent on the path you take example
here the work work is a path function
correct because from here to here if she
is going she is doing different amount
of work right if she is or if she is a
let's suppose I mean you just see the
four different paths you know and all
these different paths still have no
different amount of work you reach this
phone so the work done will be a path
function that depends on the project
correct so let's take some example for
the state and path function is volumes
Tito path function yes it is a state
function we have seen that if you are
doing a experiment
in the lab you just care about a volume
of let's suppose water or any acid
require I don't care how you got this
you get from bigger one we can do
because three till you using test-tube
you don't care
temperature yes it is a stake much why
for example same case as opposed no you
have this beaker and you want to
maintain eg Celsius for some experiment
do you care if you are getting use 80
degree Celsius from a Bunsen burner
burner here or you are putting some
immersion rod here or you got this hot
water from a user and you are using it
or you using firewood do you hear you
don't hear you don't care how this
evening this as this temperature came
whether it was a hot water from a geezer
with a Bunsen burner that I was little
but the drink is bad
oh it was a volt fire or it was a heater
you don't care or whether did you use a
microwave oven if it this one you don't
care you only care about the LEDs this
is temperature so it is also state
forest pressure
same thing with the pressure you don't
care how you got this pressure to doing
some experiment you want some let's
suppose five atmospheric pressure you
don't care how you got this whether you
need some chemical reaction to get this
pressure whether you example in this
case you you have put some iron here and
you squeeze the volume to get the
pressure or you are pressuring with your
hand you don't care or you need some
hydraulic device you don't care you only
care about let's suppose five
atmospheric pressure that's all you care
you don't care how you got this pressure
so pressure will also be a state
function
density density loss of a state but you
don't care how you got a density example
you had this water you had milk actually
had milk with some density and you want
to make it a little thicker
exactly 1 st 1 and you wanted to make it
nice to do it do thicker it will think
of more dense more dense you want make
it do you care whether if you are using
microwave oven to heat this up and
reduce density or you're using some gas
LPG gas or you are using wood do you
hear you don't hear just care about
different densities you don't care how
you got this right whether you use
microwave oh man you used it here maybe
heater to heat this boil this and review
density or did you use a LPG gas and the
gas stove and estaba or did you use a
wood you don't hear how you got this you
only care what density so it is also
stable same thing with the mass example
I want 10 kg of iron do I care if I got
this 10 kg from 10 different people each
1 kg each and I got 10 G's or do I care
if I got 2 kg 1 3 people and Fergie from
1 and I got 10 kg total or do I hear the
vigor got 10 the whole thing from my
teacher I don't care from where I got
how I got the same kg do I care if I
have put a glazing on that one I don't
hear I asked about 10 kg so it is also
state function interrelating do I care
how the Internet is G seen I don't care
I just care about the Internet in the
current internal energy of the system I
don't care how it is achieved the
internal energy also is a stable heat
his heat a stateful
this is tricky one he is not a state
nation he is a path function
see we did talk about heat we talk about
heat flow or heat transfer correct so it
suppose I take my system and I can't say
the heat is this much this you can't see
heat is applied only well let's suppose
there is a hot object and there is a
cold object when they are in touch the
heat flows from hot to cold and once
they are in equilibrium the heat doesn't
flow it
so heat flow doesn't happen always it
happens only to wreak a process where
the two objects are in different
temperature correct so I can't say that
heat is a state function that I can't
see for sure because example I have some
flasks with some water just with this
flask this and water I can tell that the
volume of this water is this small in
the state I can tell the temperature of
this water is this some Celsius so
temperature state function
I can tell the pressure here is this I
can tell the pressure also some X
atmospheric pressure I can't invest your
body so the density is also state
function I can tell the mass of what was
a mass is also stable or this I can tell
they internalized your internal GOCC
but heat I can't tell heat comes only
when this water is in touch with some
hot object a cold object and then
transfer of heat thickness right so heat
is nothing but heat flow so it is not
the state function it is not the state
correct we talk about work work is also
known as statements example I showed you
example this is one right here I have to
reach this destination
I can take this path do more work in
this this path are blue less one
similarly the next example I can take is
the length length is also not a state I
am saying that I am have to go from
point A to my point B so the length is
different if I take path 1 and if I take
part well it'll be different right all
right Nick passing length
so length is also not a state function
so if you see he'd work and length are
not a state function their path function
other things are generally state fish
also for state fertility just tell that
this is the correct
so heat and work is not a state please
note that he did work in order but the
trick part is internal energy you see it
will drag this law is nothing but heat
plus work
these two are not state function but
internal energy change is a state
function this is something it is strange
right and a good example to explain this
is for example I have to expand some gas
so from this volume I have to expand to
this one and making sure that this have
that opposed pressure per one and volume
v1 this guy also has a pressure it
expands they should even work so one we
can be if you want to maintain the
temperature if it expands since you are
keeping these constant we have this PV
is equal to NRT the ask equation we have
to supply some temperature some heat
some heat P a root of life or you want
we can expand adiabatically also where
we don't have to supply the heat and
expand in that case they'll be work done
by the system give me some volume my
system so if you see in both case the
energy change is same either this way
this is my gas I have to expand to this
this much volume right both has gas
there are two paths one option I am
saying is you read this another item
saying the work is done by system
idiotically in both case in internal
energy c barred if you see the path is
different so you see this Q and W both
are path function
the change in internal energy is a state
function we'll discuss more on these let
me take some examples similarly we
talked about a state we take an example
of a card just in case you're a little
bit confused with the thumb and I swore
let's take the car you talked about car
we talked about things like what is the
location of the sky where does point a
one point B what is the orientation
whether it's pointing with this fire or
pointing this side East Side west side
what is the speed of the car
all these are stage of the car correct
because with that C at a given point we
can tell the location orientation speed
so these are the states these are the
states which defined the state of the
car the point e supplied in Simon is
word when I say this is a flask it has
water I can say that how much volume of
water it has what is the temperature it
has what is the designate has what is
the pressure it has what is the mass of
the water it has all these are my state
function in the thermodynamics what so
similar to car we have states of the
system so they told pressure volume
temperature and the composition of the
system that is the mass of the system
example is my flask it has some water
so all these pressure volume temperature
the mass density all these things are my
state of the system the chemical system
to be more specific
and these are my state systems same as I
told state variables and other things
which depends only the state and my
examples are pressure volume temperature
internal energy mass density and we
define the chemical system by the state
variables not by the path alright so as
I told my thermodynamic system example
that we have a gas you can define the
seat of the gas by telling its pressure
volume temperature the number of moles
ejected
so those things those parameters will be
using more often to solve various
numerical
Dominic's sister and these videos
pressure volume temperature number of
moles all these are mines chain bales
correct and please note to define AG
state a system we don't define all even
if we know pressure of all living in
find temperature because we have this
gas laws so if you know some parameter
or if you know some state variable you
can very well find other signal even
also so you don't need to define all the
properties even if you have some
properties some state variables you can
find the other ones thank you visit exam
viacom to watch free educational videos
try free online tests get the best
quality study materials study from the
best tutors and mentors and much more
thanks and serene
About this Video
4.7/5 Rating
Apr 19, 2026 Last updated
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