WHY is first law of thermodynamics different in physics and chemistry
please agar accha se pata h tab hi reply karna I can't afford to be confused anymore
119 Replies
@Dexter
Note for OP
+solved @user1 @user2... to close the thread when your doubt is solved. Mention the users who helped you solve the doubt. This will be added to their stats.Sign of work done is taken differently
It's just convention
ohk
see my teacher gave a very good reasoning for this
Chemistry does the sensible thing and says that work done is positive when gas gets energy.
Physics says work done should have same sign as volume change.
so is it safe to say in physics we consider a mechanical system and in chem we consider reactions ?
Different frame of references.
No, it's the same actually.
In physics what we study in thermodynamics is Basically pistons and engines
we need work done FROM the system in physics
thats why we take expansion as positive
In chemistry the frame is the gas itself whereas in physics it is outside the gas.
but for Chemistry
Expansion will cause us more problems
we Study the system in chemistry
but we study the surroundings in physics
exactly
what no why will we study the surroundings ?
Physics law: The heat supplied is converted into expansion(work done) and change in internal energy
Chem law:The change in internal energy is the sum of the work done on the gas and the heat provided.
..
Physics mein Its like ki
you have a piston
you give gas heat
it expands
boom
work is positive in expansion because YOU got Work from this
haan woh samajh gyi
No, both definitions work for both systems. You have to interchange signs a bit.
applications ke hisaab se puch rhi thi
ohk
I use the physics def in chem and chem def in physics too. It works both ways.
Physics ka to yahi hai ki expansion is positive because displacement is in direction of pressure
Just don't mix it up with the enthalpy definition and you're good.
Yeah lmao same
like agar physics mein they make me calculate heat at constant pressure
i just calculate enthalpy
šš
ooh tell me that too whats the diff TwT
its easier that way
Yeah me too ahha
Physics ke syllabus mein to enthalpy hai hi nahi
š“
Yeah, I used to get so confused about enthalpy
This happened to me in entropy and gibbs energy
Gibbs energy to abhi tk nahi smjh aayi
i loathe thermodynamis
Enthalpy is a quantity defined as the sum of the internal energy (kinetic energy of particles) and the energy stored due to compression of the gas (pressure energy)
I like the theory, I hate the numbers.
Nah its pretty scoring bhai
Unlike mechanics
I got 15/100 on a thermo part test
In chem
I also got 95 on the thermo part test in physics.
Don't ask how.
LMFAO mera mechanics mai 90+ aaya tha mains mai
physics mein the only chapter i truly hate is fluid mechanics
Abhi aap 11vi mein ho
Fluids is nice and all, it's just a whole lot
š“š“
nahi humaara 11th and12th dono hai.. so i finished my jee mains syllabus
mechanics Ke sawaal advanced mein bohot dikkat
wait you were doing 3D a few months back no?
yes its like mixed
and tera calculus nahi hua tha us samay if i remember correctly
no its over
2 mahine mein calculus krwa diya poora??
....what is this mixed syllabus thing?
????
ššš
actually humaara college APRIL shuru hua tha
right after ICSE reuslts
I took three years for that crap
Bhai advanced level problems of fluids are really unsolvable
ššš still not perfect
like they fnished 11th 12th syllabus before March
Yeah.
and 12th is fulll revision and
boards
Lemao
ded
yeah
Too much too handle
but we get a lot of time somehow
Tenth - diff calc
Eleventh - integration
Twelfth - DEs and vector calc
And still I get low in calculus questions
Where the heck are you studying?
Calculus is pretty spontaneous
questions click krna chahiye bas
wahi
we get a lot of time since we don't get time to procrastinate
what is this pace dude
SCS
scs
Even Narayana isn't this crazy
yes
wharsdat
They finish syllabus in July.
Narayana is like this too lol.
Revision from August onwards.
Chaitanya ?
they finish 90% syllabus by Jan and few till july, just like for us
š“
We have few chapters in 12th CHEM and Physics
mujhe fomo hogaya
my syllabus got over in November
lmao
šš
My portions were till three days before my bday lol
arey time lekar padhna sahi hai, this is like some survival game
Sept end.
That's when they finished polymers and p block.
yeah dude 2 mahine mein calculus is crazy
We started revision for the other subjects by then.
hume to ek mahine bas limits padhaya tha
šš
Sri Chaitanya is the only SCS i can think of.
What's the last S?
mujhe utna kuch samajh mai nahi aaya although i was able to solve questions
they taught is p block in the end too lmao
that only maga
Ayyayyo.
we alr finsihed polymers but its not like the teachers taught us we had to learn it ourselves. isnt it deleted syllabus tho
calculus is more about concepts than questions but good for you
just keep revising shi
mains se deleted yes
Did you write this uhh 27/12/2024 paper? It says Sr.60Elite, Target sections
whats that
haan
no
oh ok chaintanya stuff
thats for Sr
My institute did till polymers, told us to self study Everyday Life.
Im JR
Oh
Ok
Dexter, I'll share the paper.
I got 139 š
It was also my first ever full syllabus test
im not in Super60 im in C120
wbhu
MUJHE BHI
PWEESE
I'm not in Chaitanya
who cares
My college pirated it to make us write lol
OLMFALDJFKLA
LMFAO
WHAT
I'll share it in media
send issok
Maths was hell
Just Assertion reason
Worst paper ever
which institude are u from ?
institude
institute*
fyck
DMs
ok
Because you actually will know the name
@minttea @Dexter
Yes I made the silliest of mistakes. Ignore those. I had not studied.
And I reckon I'd get in the 170-180 range if I wrote it blind now.
interesting one !!
the definition of 'W' in both the subjects is different (Note that, definition of work done is universal; provided the displacement and force is specified).
In Chemistry, we define 'W' as work done by the surroundings(piston) on the system (gas). so whenever gas expands, it does displacement against the force applied by the piston, which results in negative value of 'W'.
whereas,,
In Physics, we define 'W' as work done by the system (gas) on the surroundings (piston). Here say, if the gas is expanding, the displacement of the piston is in the direction of the force applied on it by the gas. so, according to the definition of 'W', its positive.
In short, the symbol 'W' has different meanings in physics and Chemistry. Its up to us, whether we are considering the force applied is by the gas or by the piston.
Conventionally, if we write 'W' in chemistry, it means work done by the piston on the system.
Technically we should specify it, inspite of writing just 'W'.
hope it helpss !!
Ask physics people
Yes sir, thank you so much!
So chemistry ppl are bankers and physics ppl are just normal ppl who get loans
Humko to simple si cheez batayi ki diffrence of of Pressure taken
Ek me Internal P is taken
Doosre me External Pressure
Idk kitna sahi hai but šš
Hn ye bhi sahi hai, kyunki in physics work DONE by sys is +ve toh by thaf we can change
But it's kinda incomplete to understand
Mere hisaab se
yeah because physics mein we rarely deal with irreversible processes
so physics wale just take Pgas=Pext
by default
hain>
all processes are irreversible no (real ones)
yeah
but physics mei we only study reversible na
Accha!