## Useful Summary of Thermodynamic Definitions

isochoric/isometric: $\Delta V = 0$
isothermal: $\Delta T = 0$
isobaric: $\Delta P = 0$

Chem_Mod
Posts: 17238
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 367 times

### Useful Summary of Thermodynamic Definitions

In class today I forgot to mention this list I created to assist students.

An adiabatically isolated system has only adiabatic boundary sectors. Energy can be transferred as work, but transfers of matter and of energy as heat are prohibited. q = 0

Isothermal
An isothermal process is a change in a system where the temperature stays constant: ΔT = 0.

Isobaric
An isobaric process is a change in a system where the pressure stays constant: ΔP = 0.

Isochoric
An isochoric process is a change in a system where the volume stays constant: ΔV = 0.

Intensive property
An intensive property is a bulk property, meaning that it is a physical property of a system that does not depend on the system size or the amount of material in the system.

Note: The ratio of two extensive properties of the same object or system is an intensive property. For example, the ratio of an object's mass and volume, which are two extensive properties, is density, which is an intensive property.

State Function
A state function describes a physical property of the system and is independent of how the system arrived at its present condition.

Stevie Wisz
Posts: 59
Joined: Fri Sep 25, 2015 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

Thank you!! :)

jennymai96
Posts: 5
Joined: Fri Sep 25, 2015 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

So for adiabatic system, the energy as heat is different from the energy as work? Thanks!

Evelin Escobedo
Posts: 14
Joined: Fri Sep 25, 2015 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

This is going to be helpful when trying to keep track of the different vocab this quarter. Thanks!
Is this the main list for thermodynamics, or would it be recommended to extend the list on out own ?

Melissa Kulon 2D
Posts: 22
Joined: Fri Sep 25, 2015 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

Thank you! Just to clarify, are the only terms that are NOT state functions, work and heat?

chrispolo15
Posts: 13
Joined: Fri Sep 25, 2015 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

can someone elaborate on state functions? i'm still kind of confused. are they dependent or dependent?

VivianYang2A
Posts: 8
Joined: Fri Sep 25, 2015 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

chrispolo15 wrote:can someone elaborate on state functions? i'm still kind of confused. are they dependent or dependent?

State functions are dependent on the state of the moment (temp/press/vol), but are independent of system "history"; I think it's more important to note that they are additive, like what we do with Hess's Law in enthalpy.

Rhiannon Imbeah 2I
Posts: 30
Joined: Fri Sep 25, 2015 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

Thank you for posting this!

204635822
Posts: 25
Joined: Fri Sep 25, 2015 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

chrispolo15 wrote:can someone elaborate on state functions? i'm still kind of confused. are they dependent or dependent?

For a state property, you only need to know initial and final values. The pathway is not important.

Brianna
Posts: 13
Joined: Fri Sep 25, 2015 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

jennymai96 wrote:So for adiabatic system, the energy as heat is different from the energy as work? Thanks!

energy as heat is always separate from energy as work. For Adiabatic systems, since there is no heat transfer, q=0 and Delta U = w

carissa1F
Posts: 7
Joined: Sat Nov 23, 2013 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

can someone elaborate more on the adiabetic system and its conditions?

Karina Saucedo 2I
Posts: 4
Joined: Fri Sep 20, 2013 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

Adiabatic as also defined in the textbook is, "not permitting or accompanied by the passage of energy as heat." This can be be categorized into two different processes, reversible and irreversible. Reversible is quasi-static where as the irreversible process is spontaneous since there is a big change in the external restriction. For reversible, quasi-static, it starts were gas pressure equals external pressure then there is a change externally where there is a slight decrease in the outside pressure. Therefore the gas expands just a bit before reaching equilibrium which occurs in a fast pace. This process is repeated until the desired pressure is reached. On the other hand if the outside pressure greatly decreased rapidly than the gas would expand until it reached equilibrium this process however will do so in a different manner than the reversible process.

Rachel Lipman
Posts: 45
Joined: Fri Sep 25, 2015 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

This is great! Thank you for sharing these key terms in such a simple and concise way! These terms are essential to memorize for future quizzes and tests.

Sochima1J
Posts: 2
Joined: Mon Jan 26, 2015 2:17 pm

### Re: Useful Summary of Thermodynamic Definitions

I agree! This is really helpful.

Crystal Ma
Posts: 9
Joined: Fri Sep 25, 2015 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

Thank you!!

Katelyn 2E
Posts: 35
Joined: Sat Jul 22, 2017 3:01 am

### Re: Useful Summary of Thermodynamic Definitions

will we be discussing these different types of systems each in detail or should we just know the general conceptual idea behind them such as is provided here? thank you!

Michelle Steinberg2J
Posts: 73
Joined: Fri Sep 29, 2017 7:04 am

### Re: Useful Summary of Thermodynamic Definitions

Would someone be able to briefly explain the difference between isobaric, isochoric, and isothermal? I have these definitions written down and I've read through the textbook, but I feel as though I've memorized the differences and don't fully grasp the concept. Thanks!

Kailey Brodeur 1J
Posts: 34
Joined: Thu Jul 27, 2017 3:00 am

### Re: Useful Summary of Thermodynamic Definitions

These 3 situations each have a different factor that remains the same. Isobaric refers to a system in which pressure remains constant, isochloric refers to a system in which volume remains constant, and isothermal refers to a system in which temperature remains constant. This means other factors are changing in order to change the entropy of a system. This is important because we use different equations in order to calculate entropy change based upon what the system's constants and variables are.

Rishi Khettry 1L
Posts: 29
Joined: Fri Sep 29, 2017 7:05 am

### Re: Useful Summary of Thermodynamic Definitions

To clarify, intensive properties are ratios. For example, density would be an intensive property because it is mass/volume. Where mass and volume are both extensive properties.

Angela 1K
Posts: 80
Joined: Fri Sep 29, 2017 7:05 am

### Re: Useful Summary of Thermodynamic Definitions

Michelle Steinberg2J wrote:Would someone be able to briefly explain the difference between isobaric, isochoric, and isothermal? I have these definitions written down and I've read through the textbook, but I feel as though I've memorized the differences and don't fully grasp the concept. Thanks!

As Dr. Lavelle explained in his post,
Isobaric : constant pressure
Isochoric: constant volume
Isothermal: constant temperature

Brian Kwak 1D
Posts: 88
Joined: Fri Sep 28, 2018 12:17 am

### Re: Useful Summary of Thermodynamic Definitions

Just asking for clarification but for an Adiabatic isolated system as dr.lavelle stated that there can be exchange or more specificly loss of internal energy as work correct? So compared to an isolated system where there is no exchange of matter or energy because there is no surroundings therefore meaning that the internal energy is constant and doesn’t change for a Adiabatic isolated system the internal energy can DECREASE due to work correct? So between the two essentially the only difference would be that an Adiabatic system can lose internal energy as work because work is not within the limits of the Adiabatic boundaries correct? Verses the isolated system where there is absolutely no exchange of energy or matter because the system is “isolated” surroundings therefore meaning that there is no change at all in internal energy.

Nikki Bych 1I
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

### Re: Useful Summary of Thermodynamic Definitions

I am having trouble distinguishing the difference between a state function and an intensive property, they seem very similar to me.

Abby-Hile-1F
Posts: 46
Joined: Fri Sep 28, 2018 12:16 am

### Re: Useful Summary of Thermodynamic Definitions

will we need to identify processes as isobaric, isochoric, or isothermal?

Matthew Casillas 1C
Posts: 29
Joined: Fri Sep 28, 2018 12:21 am

### Re: Useful Summary of Thermodynamic Definitions

Abby-Hile-1F wrote:will we need to identify processes as isobaric, isochoric, or isothermal?
I don't believe so, I think they tell us in the question so we use specific equations.