I
iTeachChem•4mo ago
minttea

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
121 Replies
iTeachChem Helper
iTeachChem Helper•4mo ago
@Dexter
iTeachChem Helper
iTeachChem Helper•4mo ago
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.
Opt
Opt•4mo ago
Sign of work done is taken differently It's just convention
minttea
mintteaOP•4mo ago
ohk
Dexter
Dexter•4mo ago
see my teacher gave a very good reasoning for this
Opt
Opt•4mo ago
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.
minttea
mintteaOP•4mo ago
so is it safe to say in physics we consider a mechanical system and in chem we consider reactions ?
SirLancelotDuLac
SirLancelotDuLac•4mo ago
Different frame of references.
Opt
Opt•4mo ago
No, it's the same actually.
Dexter
Dexter•4mo ago
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
SirLancelotDuLac
SirLancelotDuLac•4mo ago
In chemistry the frame is the gas itself whereas in physics it is outside the gas.
Dexter
Dexter•4mo ago
but for Chemistry Expansion will cause us more problems we Study the system in chemistry but we study the surroundings in physics exactly
minttea
mintteaOP•4mo ago
what no why will we study the surroundings ?
Opt
Opt•4mo ago
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.
minttea
mintteaOP•4mo ago
..
Dexter
Dexter•4mo ago
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
minttea
mintteaOP•4mo ago
haan woh samajh gyi
Opt
Opt•4mo ago
No, both definitions work for both systems. You have to interchange signs a bit.
minttea
mintteaOP•4mo ago
applications ke hisaab se puch rhi thi ohk
Opt
Opt•4mo ago
I use the physics def in chem and chem def in physics too. It works both ways.
Dexter
Dexter•4mo ago
Physics ka to yahi hai ki expansion is positive because displacement is in direction of pressure
Opt
Opt•4mo ago
Just don't mix it up with the enthalpy definition and you're good.
Dexter
Dexter•4mo ago
Yeah lmao same like agar physics mein they make me calculate heat at constant pressure i just calculate enthalpy šŸ˜†šŸ˜†
minttea
mintteaOP•4mo ago
ooh tell me that too whats the diff TwT
Dexter
Dexter•4mo ago
its easier that way
minttea
mintteaOP•4mo ago
Yeah me too ahha
Dexter
Dexter•4mo ago
Physics ke syllabus mein to enthalpy hai hi nahi 🐓
Opt
Opt•4mo ago
Yeah, I used to get so confused about enthalpy
Dexter
Dexter•4mo ago
This happened to me in entropy and gibbs energy Gibbs energy to abhi tk nahi smjh aayi
minttea
mintteaOP•4mo ago
i loathe thermodynamis
Opt
Opt•4mo ago
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.
Dexter
Dexter•4mo ago
Nah its pretty scoring bhai Unlike mechanics
Opt
Opt•4mo ago
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.
minttea
mintteaOP•4mo ago
LMFAO mera mechanics mai 90+ aaya tha mains mai
Dexter
Dexter•4mo ago
physics mein the only chapter i truly hate is fluid mechanics Abhi aap 11vi mein ho
Opt
Opt•4mo ago
Fluids is nice and all, it's just a whole lot
Dexter
Dexter•4mo ago
🐓🐓
minttea
mintteaOP•4mo ago
nahi humaara 11th and12th dono hai.. so i finished my jee mains syllabus
Dexter
Dexter•4mo ago
mechanics Ke sawaal advanced mein bohot dikkat wait you were doing 3D a few months back no?
minttea
mintteaOP•4mo ago
yes its like mixed
Dexter
Dexter•4mo ago
and tera calculus nahi hua tha us samay if i remember correctly
minttea
mintteaOP•4mo ago
no its over
Dexter
Dexter•4mo ago
2 mahine mein calculus krwa diya poora??
Opt
Opt•4mo ago
....what is this mixed syllabus thing?
Dexter
Dexter•4mo ago
???? 😭😭😭
minttea
mintteaOP•4mo ago
actually humaara college APRIL shuru hua tha right after ICSE reuslts
Opt
Opt•4mo ago
I took three years for that crap
Dexter
Dexter•4mo ago
Bhai advanced level problems of fluids are really unsolvable 😭😭😭 still not perfect
minttea
mintteaOP•4mo ago
like they fnished 11th 12th syllabus before March
Opt
Opt•4mo ago
Yeah.
minttea
mintteaOP•4mo ago
and 12th is fulll revision and boards
Dexter
Dexter•4mo ago
Lemao ded
minttea
mintteaOP•4mo ago
yeah
Dexter
Dexter•4mo ago
Too much too handle
minttea
mintteaOP•4mo ago
but we get a lot of time somehow
Opt
Opt•4mo ago
Tenth - diff calc Eleventh - integration Twelfth - DEs and vector calc And still I get low in calculus questions Where the heck are you studying?
Dexter
Dexter•4mo ago
Calculus is pretty spontaneous questions click krna chahiye bas wahi
minttea
mintteaOP•4mo ago
we get a lot of time since we don't get time to procrastinate
Dexter
Dexter•4mo ago
what is this pace dude
minttea
mintteaOP•4mo ago
SCS
Dexter
Dexter•4mo ago
scs
Opt
Opt•4mo ago
Even Narayana isn't this crazy
minttea
mintteaOP•4mo ago
yes
Dexter
Dexter•4mo ago
wharsdat
Opt
Opt•4mo ago
They finish syllabus in July.
minttea
mintteaOP•4mo ago
Narayana is like this too lol.
Opt
Opt•4mo ago
Revision from August onwards. Chaitanya ?
minttea
mintteaOP•4mo ago
they finish 90% syllabus by Jan and few till july, just like for us
Dexter
Dexter•4mo ago
🐓
minttea
mintteaOP•4mo ago
We have few chapters in 12th CHEM and Physics
Dexter
Dexter•4mo ago
mujhe fomo hogaya my syllabus got over in November lmao 😭😭
Opt
Opt•4mo ago
My portions were till three days before my bday lol
minttea
mintteaOP•4mo ago
arey time lekar padhna sahi hai, this is like some survival game
Opt
Opt•4mo ago
Sept end. That's when they finished polymers and p block.
Dexter
Dexter•4mo ago
yeah dude 2 mahine mein calculus is crazy
Opt
Opt•4mo ago
We started revision for the other subjects by then.
Dexter
Dexter•4mo ago
hume to ek mahine bas limits padhaya tha 😭😭
Opt
Opt•4mo ago
Sri Chaitanya is the only SCS i can think of. What's the last S?
minttea
mintteaOP•4mo ago
mujhe utna kuch samajh mai nahi aaya although i was able to solve questions
Dexter
Dexter•4mo ago
they taught is p block in the end too lmao
minttea
mintteaOP•4mo ago
that only maga
Opt
Opt•4mo ago
Ayyayyo.
minttea
mintteaOP•4mo ago
we alr finsihed polymers but its not like the teachers taught us we had to learn it ourselves. isnt it deleted syllabus tho
Dexter
Dexter•4mo ago
calculus is more about concepts than questions but good for you just keep revising shi mains se deleted yes
Opt
Opt•4mo ago
Did you write this uhh 27/12/2024 paper? It says Sr.60Elite, Target sections
Dexter
Dexter•4mo ago
whats that
minttea
mintteaOP•4mo ago
haan no
Dexter
Dexter•4mo ago
oh ok chaintanya stuff
minttea
mintteaOP•4mo ago
thats for Sr
Opt
Opt•4mo ago
My institute did till polymers, told us to self study Everyday Life.
minttea
mintteaOP•4mo ago
Im JR
Opt
Opt•4mo ago
Oh Ok Dexter, I'll share the paper. I got 139 šŸ’€ It was also my first ever full syllabus test
minttea
mintteaOP•4mo ago
im not in Super60 im in C120 wbhu MUJHE BHI PWEESE
Opt
Opt•4mo ago
I'm not in Chaitanya
minttea
mintteaOP•4mo ago
who cares
Opt
Opt•4mo ago
My college pirated it to make us write lol
minttea
mintteaOP•4mo ago
OLMFALDJFKLA LMFAO WHAT
Opt
Opt•4mo ago
I'll share it in media
minttea
mintteaOP•4mo ago
send issok
Opt
Opt•4mo ago
Maths was hell Just Assertion reason Worst paper ever
minttea
mintteaOP•4mo ago
which institude are u from ? institude institute* fyck
Opt
Opt•4mo ago
DMs
minttea
mintteaOP•4mo ago
ok
Opt
Opt•4mo ago
Because you actually will know the name
Opt
Opt•4mo ago
@minttea @Dexter Yes I made the silliest of mistakes. Ignore those. I had not studied.
Opt
Opt•4mo ago
And I reckon I'd get in the 170-180 range if I wrote it blind now.
aspargine
aspargine•4mo ago
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 !!
iTeachChem
iTeachChem•4mo ago
Ask physics people
minttea
mintteaOP•4mo ago
Yes sir, thank you so much! So chemistry ppl are bankers and physics ppl are just normal ppl who get loans
flower
flower•4mo ago
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 šŸ™šŸ™
minttea
mintteaOP•4mo ago
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
Dexter
Dexter•4mo ago
yeah because physics mein we rarely deal with irreversible processes so physics wale just take Pgas=Pext by default
iTeachChem
iTeachChem•4mo ago
hain> all processes are irreversible no (real ones)
Dexter
Dexter•4mo ago
yeah but physics mei we only study reversible na
iTeachChem
iTeachChem•3mo ago
Accha! +solved @Opt @Dexter
iTeachChem Helper
iTeachChem Helper•3mo ago
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iTeachChem
iTeachChem•3mo ago
YES @nermal @į“˜ÉŖį“„į“„ŹœÉŖ | šŸŽ§ šŸŽ¶ wooohooo ty <3

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