What is Isothermal: Definition and 227 Discussions

In thermodynamics, an isothermal process is a type of thermodynamic process in which the temperature of the system remains constant: ΔT = 0. This typically occurs when a system is in contact with an outside thermal reservoir, and the change in the system will occur slowly enough to allow the system to continue to adjust to the temperature of the reservoir through heat exchange (see quasi-equilibrium). In contrast, an adiabatic process is where a system exchanges no heat with its surroundings (Q = 0).
Simply, we can say that in isothermal process




T
=

constant



{\displaystyle T={\text{constant}}}





Δ
T
=
0


{\displaystyle \Delta T=0}





d
T
=
0


{\displaystyle dT=0}

For ideal gases only, internal energy



Δ
U
=
0


{\displaystyle \Delta U=0}
while in adiabatic processes:




Q
=
0.


{\displaystyle Q=0.}

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  1. C

    Is a reversible isothermal process truly without energy change?

    Hi! I was just wondering if in a reversible isothermal process, there is a change in internal energy. I know that for the isothermal forward process the temperature is constant so internal energy is constant? What really stumps me is the word reversible.
  2. R

    Question on Thermodynamics (adiabatic and isothermal expansions)

    Homework Statement A cubic metre of air at 0degreesC and 1 atm is compressed reversibly to 10 atm. (a) What is the final temperature if it is compressed adiabatically? (b) How much heat must be removed if it is compressed isothermally? I understand what the two different terms...
  3. T

    Change in entropy, Gibbs and Helmholtz in an isothermal compression

    Homework Statement Determine the change in the entropy, Helmholtz free energy, and Gibbs free energy, when a mole of ideal gas is compressed from 1atm to 100atm at 20C. The Attempt at a Solution I am not entirely convinced by my attempt below -- can anyone spot something wrong? (I thought it...
  4. Q

    Isothermal titration calorimetry

    Homework Statement Using isothermal titration calorimetry, you calculate \DeltaH^{o}_{bind} (= -5000 cal/mol) for a protein-ligand binding reaction at 25°C. You then perform a separate assay in which you measure equilibrium ligand binding at two different temperatures: L_{0} (nM)...
  5. L

    Isothermal and reversible expansion work problem (Physical Chem)

    Homework Statement A sample of 2.00 mol. CH3OH (g) is condensed isothermally and reversibly to liquid at 64*C. The standard enthalpy of condensation of methanol @ 64*C is -35.3 kJ/mol. Find w and q for the reaction. Homework Equations w = -nRT * ln(Vf/Vi) (although I don't have volume...
  6. C

    Need help regarding finding out the max pressure in a isothermal cycle.

    A volume of 1.5 m3 of air initially at 1.31 bar and 293k undergoes three processes in order to complete a cycle: Process 1 to 2 Isothermal compression from state 1 through a volumetric compression ratio of Rv to state 2 2 to 3 Isobaric heating back to the original volume. 3 to 1...
  7. C

    Isothermal increase in pressure of solids

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  8. G

    Isothermal Process: Constant Temperature & Heat Capacity?

    In an isothermal process, does the temperature of an ideal gas remain constant? And if so does the heat capacity at constant volume = zero?
  9. B

    Understanding Isothermal Processes

    I've gone through a some of our textbooks but none of them effectively explains this process clearly. For the isothermal process, according to the first law of thermodynamics, ΔU = 0, indicating that Q = -W. So if heat flows into the system, all the energy put in is converted to work which the...
  10. M

    Confused about isothermal processes

    We are currently learning about isothermal processes in class and there's something i don't really get. i can visualize what happens when the piston is pulled or pushed very slowly, PV = constant and hence produces an isotherm on a PV diagram. And if since the temperature is constant...
  11. P

    Isothermal means constant temperture process

    Isothermal means constant temperture process. But thermal means heat. Presumably iso is short for isolated. So it should be isolated heat process or constant heat process rather than constant temperture process. Instead adiabatic means constant heat process. Even though it is a trivial matter, I...
  12. M

    Isothermal or adiabatic process

    :confused: :confused: i was reading my lecture note over the half term but i am still a bit confused and i was wondering if someone could describe in detail, using a p-v diagram, a well known engineering cycle which specifies a isothermal or adiabatic process. Thanks you very much
  13. T

    Isothermal Temperature: Real Life Examples of Constant Heat Flow

    I need to give examples of an instance in which temperature remains constant when heat flows in and out of a system, isothermal by definition. I know the textbook example (slowly heating an ideal gas in a cylinder with a piston on one end, volume increases as pressure decreases, etc.), but are...
  14. M

    Van der waal gas in isothermal free expansion

    Homework Statement A gas obeys the Van Der Waal equation of state. The gas undergoes a free expansion from volume Vi to Vf at a constant temperature T. Find the change in entropy of the gas.Homework Equations du=Tds-Pdv+mdn The Attempt at a Solution I can solve the problem assuming du= 0 but...
  15. F

    How Does Isothermal Expansion Affect Work Done and Temperature in an Ideal Gas?

    Suppose 145 moles of a monatomic ideal gas undergo an isothermal expansion from 1.00m^3 to 4.00m^3, as shown in figure. what is the temp at the beginning and end of this process? how much work is done by the gas during the expansion? http://www.physics.brocku.ca/Courses/1p23/images/FG18_24.JPG...
  16. C

    Adiabatic, isothermal, or isovolumetric

    Here's my problem: 300 calories of heat are added to a gas as the internal energy of the gas increases by 500 calories. The described thermodynamic process is best described as? My guess is that the process is isothermal b/c work is being done in the system.
  17. M

    Help! I Need a Hint on Isothermal Balloon Expansion Problem

    I got stuck on the following problem, which is very important for my exam preparations - would anyone mind giving me a hint? A balloon of Volume V(0) is tethered to the ground using a light cable. It is filled with helium gas of density rho (He). At ground level the pressure and density in...
  18. P

    Find Work of Isothermal Expansion: Questions Answered

    have a question. the viral eqn of state for one mole of aragon is: pV=RT(1+B/V +c/V^2) T is known and so is B and C. but p is not known. initial V is known and so is final V. the question is "find out the work of a reversible isothermal expansion at this temperature" Know I'm wondering is...
  19. J

    Statistical Mechanics to Thermo for Isothermal Isobaric Ensemble

    I am trying to make the connection from statistical mechanics to thermodynamics for the isothermal isobaric ensemble. Partition function = (sum of)exp(-BEj-gamma*Vj). I have followed T.L. Hill [Statistical Mechanics, p. 67] but can not understand how he justifies dE=(sum of)EdP, rather than...
  20. S

    Analyzing Dark Matter Halos: Isothermal vs NFW Profiles

    Hi all, I have currently been reading up on dark matter halos as I’m considering doing a small project on them for my degree. I plan to use an (approximated) analytical equation for the density at r of an isothermal halo in terms of the halos central density and core radius. density(r) =...
  21. I

    Solving Isothermal Expansion of an Ideal Monatomic Gas

    ok i really don't understand this question, especially about finding the functions for the recompressed isothermal and about the recompression stuff, I am just stuck An ideal monatomic gas is expanded from initial volume V1 = 1 litre, P1 = 2atm, and T1 = 300K to a volume V2 = 2 litres, and P2...
  22. S

    Solve Isothermal Expansion - Pressure, Volume & Work Explained

    If air has a pressure of 40 psig and a volume of 8 cu. ft. expands isothermally to a pressure of 10 psig, find the external work performed during the expansion. How do I do this, do I first have to change 40 psig to psia, and how do I do that? This question has me lost! Any help appreciated...
  23. B

    Calculating Isothermal Expansion Work - 2 Moles Ideal Gas, 380K

    Hello, I have what should be an easy problem, but I, of course, am having some issues. Here's the problem: The temperature of 2 moles if an ideal gas is 380 K. How much work does the gas do in expanding isothermally to 3 times its initial volume? So I know I'm going to to need to use...
  24. J

    Quasistatic isothermal expansion

    How would I show that during quastatic isothermal expansion of a monatomic ideal gas, the change in entropy is related to the heat input Q by the simple formula: delta S=Q/T Show that it is not valid for the free expansion process described. Answer: Putting heat into a system always...
  25. A

    Isothermal compressibility & Volume expansitivity

    I need equations for Isothermal compressibility & Volume expansitivity in terms of temperature and pressure. Please help. It is for refrigerants in both liquid but especially gaseous phase. Ade:wink:
  26. Z

    Isothermal compression of monatomic gas ?

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  27. D

    How Do Isothermal and Isochronic Processes Compare in Thermodynamics?

    Hello again, Last question for a while kinda confused between these two. Let's say i have these two processes, the internal energy of a system is removed(isothermal) and decreases by 50J(both of them). Now for isothermal Q=W which would tell me that work equals 50J, correct and...
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