What is Adiabatic: Definition and 494 Discussions

In thermodynamics, an adiabatic process (from the Greek adiábatos, meaning “impassable”) is a type of thermodynamic process which occurs without transferring heat or mass between the system and its surroundings. Unlike an isothermal process, an adiabatic process transfers energy to the surroundings only as work. It also conceptually supports the theory used to explain the first law of thermodynamics and is therefore a key thermodynamic concept.
Some chemical and physical processes occur too rapidly for energy to enter or leave the system as heat, allowing a convenient "adiabatic approximation". For example, the adiabatic flame temperature uses this approximation to calculate the upper limit of flame temperature by assuming combustion loses no heat to its surroundings.
In meteorology and oceanography, adiabatic cooling produces condensation of moisture or salinity, oversaturating the parcel. Therefore, the excess must be removed. There, the process becomes a pseudo-adiabatic process whereby the liquid water or salt that condenses is assumed to be removed upon formation by idealized instantaneous precipitation. The pseudoadiabatic process is only defined for expansion because a compressed parcel becomes warmer and remains undersaturated.

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  1. H

    Filling Flat Tire - Adiabatic Reversible Process

    Homework Statement A nearly flat bicycle tire becomes noticeably warmer after it has been pumped up. Approximate this process as a reversible adiabatic compression. Take the initial P and T of the air (before it is put into the tire) to be 1.00 bar and 298.0K. The final volume of air (after it...
  2. S

    Work in Adiabatic/ Isothermal and Piston

    Homework Statement Is work greater in adiabatic or isothermal process? A piston with oxygen has a final volume 1/4 the initial. The temperature is also 5 times greater. Determine pressure change, heat released or absorbed, and work done on or by gas. Homework Equations the work for adiabatic...
  3. R

    Are these two equations for adiabatic processes the same

    Hi. I was just wondering about this because is most texts I've seen this one: Tf/Ti = (Vi/Vf)^y - 1 y= gamma (Cp/CV) However, in my worksheets I always see this one: Tf/Ti = (Vf/Vi)^1 -y And actually, when I tried to solve one problem, I tried to use the first one but the...
  4. S

    Thermaldynamics - Adiabatic system W = delta(U)

    Homework Statement After integrating the pressure formula of an adiabatic system, I have to show how this is equal to the change in energy. I know that my integral is correct (it was very straight forward), but I'm having trouble showing that it is equal to \DeltaU. Homework Equations...
  5. R

    Problem about adiabatic expansion of gases

    Hello everyone. I would like to know if I did this correctly. Homework Statement Calculate the heat, internal energy and work of 1 mol of hydrogen, which undergoes a reversible adiabatic expansion from a volume of 5.25 m^3 at 300 K to a volume of 25.5 m^3 The Attempt at a Solution...
  6. 1

    Born oppenheimer approximation vs adiabatic approximation

    I'm learning to deal with h2+ (hydrogen ion) problems and the like, which sure entails the infamous born oppenheimer approximation . i know the word "adiabatic" in a thermal sense, that is , an adiabatic process is the one in which no heat transfer occurs between the things of question and...
  7. O

    Reversable process with adiabatic expansion

    Homework Statement One mole of a monatomic ideal gas is taken through the reversible cycle shown below. http://img508.imageshack.us/img508/2595/newbitmapimageqm.png process bc is an adiabatic expansion, with P_b = 10.00 atm and V_b = 10^-3 m^3. Find (a) the energy added to the gas as heat...
  8. O

    Quickly Thermo Single-Component Adiabatic System Derive Energy Equation

    Homework Statement Show that if a single-component system is such that PVk is constant in an adiabatic process (k is a positive constant) the energy is U = [1/(k-1)]PV + Nf(PVk/Nk) where f is an arbitrary function.Homework Equations Fundamental relation: U = [1/(k-1)]PV + Nf(PVk/Nk). State...
  9. Q

    Adiabatic expansion of real vs ideal gas

    for the adiabatic expansion of a gas, why is the temperature drop smaller for a real gas , vs a bigger drop for an ideal gas even though the change in internal energy is greater for a real gas , vs a smaller change for an ideal gas assuming starting temperature, and volume change are the...
  10. Q

    Adiabatic Expansion of Gas: Does the Number of Moles Affect the Calculation?

    for 1 mole of gas, the adiabatic factor gamma is given by Cp,m / Cv,m where the C are molar heat capacities so if now i have 2 moles of gas will my calculation change at all? for example, if i use PVgamma = PVgamma will anything change? it seems weird, it doesn't depend on the...
  11. N

    Thermodynamics problem: Adiabatic free expansion

    Homework Statement A rigid ( ie. Constant volume), non-conducting ( ie. Perfectly insulated, no heat losses or gain) tank with a volume of 4.6 m^3. The tank is divided into two unequal parts by a thin membrane. One side of the membrane representing 1/3 of the tank is filled with nitrogen ( may...
  12. T

    Adiabatic piston-cylinder problems always constant temperature?

    Okay I think I get this but I just want to make sure: In a frictionless, fully insulated piston-cylinder arrangement, when an external force is applied to the piston and the gas inside the cylinder is compressed, the temperature of the gas remains constant, and none of the work done to the...
  13. A

    Gas Expansions: Monoatomic vs Diatomic - Adiabatic Curve Slope Comparison

    if there are two diabatic expansions of gases A and B and slope of their P/V curve are in this way: slopeA> slopeB then which gas is monoatomic and which is diatomic?
  14. K

    Molecular work in an Adiabatic process ?

    Molecular "work" in an Adiabatic process ? I have studied Adiabatic cooling in connection with a rising parcel of air. I’m confused. I understand that temperature is a macroscopic principle (not a Microscopic); molecules do not have a temperature, only velocity and Kinetic energy. I have read...
  15. V

    How to find maximum work done in an adiabatic process?

    My Question - Steam at 200 psi and 600 F flows through a turbine operating adiabatically and exits at atmospheric pressure. For every kilogram of steam flowing through the turbine there are 150 Btu of shaft work delivered. (a) What is the final condition of the exit steam? (b) What is the...
  16. M

    Adiabatic piston expansion with friction

    An ideal gas is contained in a piston-cylinder arrangement. The walls of the cylinder and the piston itself are "adiabatic", i.e. no heat energy can be exchanged between the piston-cylinder and its surroundings. The piston experiences friction as it moves. All the heat generated by the...
  17. S

    Irrev. adiabatic process entropy >0 or =0?

    My textbook says that Delta S (sys) > 0 for irrev. ad. proc., closed syst (or see http://www.britannica.com/EBchecked/topic/5898/adiabatic-process if you don't believe me) but since Delta S = 0 for reversible adiabatic process and entropy is a state function, shouldn't Delta S = 0 for...
  18. D

    Adiabatic approxmation, estimate of d\phi/dx

    Hi, Messiah writes in his Quantum Mechanics book in chapter XVIII, section 14 (pages 786-789): http://img827.imageshack.us/img827/4605/screenshot3si.png What does he mean, when he says "an increment of the order of 'a' is necessary to transform the function phi into a function that is...
  19. H

    Clement Desmorme's experiment for Adiabatic Index gamma

    Homework Statement Basically the experiment itself can be found in here: http://www.ce.tuiasi.ro/romana/publicatii/cursuri/radinschi_fizica/Lab2%20engleza.pdf or here: http://blog.cencophysics.com/2010/02/clement-desormes-experiment/ The experiment and all the necessary calculations...
  20. W

    Energy Change in Reversible Adiabatic Expansion of a van der Waals gas

    Homework Statement Suppose the equation of state of a gas is Beta p=rho/(1-b rho) - beta a rho^2 where beta=1/kb T, b is a constant and rho is the molecular density, N/V. The internal energy of this gas is given by U=(5/2)N kb T - N a rho Determine the final internal energy of the gas...
  21. C

    Adiabatic Expansion of a real gas

    I am having trouble with the very last part of this question. I will write the whole question just to make sure that I haven't screwed up the first part too :) When a certain freon used in refrigeration was expanded adiabatically from an initial pressure of 32 atm and 0degrees C to a final...
  22. B

    Isothermal, adiabatic, isovolumetric process

    Homework Statement Air with the mass of 10kg, with pressure 15 bar and temperature 50 C comes to a isobaric expansion to 3 times the original volume, then the air cools to the pressure of 6 bar(isovolumetricly). After that it comes to adiabatic expansion to original temperature (50 C i guess)...
  23. A

    Work done for an adiabatic process

    Hi, In deriving the equation for adiabats : V^{\gamma}P = C. It is assumed that the work done during the process is W = -P \Delta V. But calculating the work done from V^{\gamma}P = C we obtain: W = \frac{C}{1-\gamma}\left[ V^{1-\gamma}_{f} - V^{1-\gamma}_{i} \right] . Also, i believe to...
  24. S

    What is the definition of adiabatic CMb spectrum in simple inflationary models?

    Can someone give a clear definition of what we mean when we say the CMb spectrum is adiabatic and what it means for simple infaltionary models?
  25. Z

    An adiabatic piston of mass m .

    An adiabatic piston of mass m... Homework Statement An adiabatic piston of mass m equally divides a diathermic container of volume V and length l. A light spring connects the piston to the right wall. In equilibrium pressure on each side of the piston is P. The container starts moving with...
  26. A

    Reversible Adiabatic Expansion for an Ideal Gas

    Homework Statement 1 mole of a monoatomic gas undergoes reversible expansion from 30 L and 400K to 60 L. The molar heat capacity in this situation is (3/2)R, independent of temperature. Calculate the final pressure and temperature of this process if it is adiabatic. Homework...
  27. D

    Adiabatic, Ideal gas, changing heat capacity, work calculation

    1. Propane vapour (1kmol) at a pressure of 40 bar and 230 C expands adiabatically to 0.25 bar and 95 C. Determine a)W, b)Delta S, c)The amount of work obtained if the expansion were done reversibly from the same initial conditions to the final pressure of 0.25bar 2. I am not sure how to...
  28. C

    Thermodynamics - Adiabatic Process

    Homework Statement A cylinder, A, containing a monatomic ideal gas, is fitted with a frictionless leakfree piston. The axis of the cylinder is oriented vertically, as in the figure below, so that the weight of the piston maintains the gas at a constant pressure P0. The cylinder is linked...
  29. Z

    Irreversible adiabatic process

    What is the concept behind 'irreversible adiabatic process' ? Why is the expression for work done in this case different from that when it is reversible?
  30. davidjonsson

    The adiabatic heat gradient is temperature dependent

    The adiabatic heat gradient is determined as \gamma = \frac{g}{c_{p}} where \gamma is the rate that temperature falls when rising in an atmosphere. g is gravitational acceleration and c_{p} is the heat apacity. On Earth it is 9.8 Kelvin per kilometer close to the surface of the Earth...
  31. V

    Adiabatic Process and the speed of sound

    Hi all, Sorry if this post is a bit wordy but I've been going round in circles and I thought I'd see if anyone on here can help, it's also my first post so be nice... I've been trying to understand how Newton miscalculated the speed of sound. I know that he thought that the propagation of...
  32. N

    Understanding Work and Energy Transfer in Adiabatic Systems

    Hello! I'm not sure if this should be in the physics section or chemistry, but I think it's covered in both. I apologise if this has been asked numerous times before! I am interested in the following adiabatic system, I think it counts as an isolated system: Here is my attempt to...
  33. P

    Entropy for adiabatic expansion

    How do I calculate the entropy of the surroundings for an adiabatic expansion? I know \DeltaSsur = qrev/T for reversible process and qirrev/T for irreversible process. But q=0 for adiabatic process, so are there any other formulas that I could use to calculate \DeltaSsurr (I know there is a...
  34. R

    Adiabatic expansion of an ideal gas.

    Problem: One mole of a diatomic ideal gas, initially having pressure P and volume V, expands so as to have pressure 2P and volume 4V. Determine the entropy change of the gas in the process. Attempt: I thought this would just be R ln(V2/V1)... So, I said (8.314)*ln(4) but it's wrong...
  35. A

    Infinite Square Well with an Adiabatic Evolution

    Homework Statement I'm trying to find the geometric phase for the adiabatic widening of the infinite square well. Griffiths defines the geometric phase to be: \gamma=i* \int^{w2}_{w1}<\psi_{n}|\frac{d\psi_{n}}{dR}>dR Where R is the aspect of the potential that is changing and w1, w2 are the...
  36. B

    Change in entropy for adiabatic compression

    Homework Statement A sample of 8.02*10^-1 moles of nitrogen gas (\gamma=1.4) occupies a volume of 2*10^-2m^3 at pressure 1*10^5pa and temperature 300K. The gas is adiabatically compressed to half its original volume. What is the change in entropy of the gas? Homework Equations...
  37. U

    Adiabatic process thermodynamics help

    Homework Statement An ideal diatomic gas at 75 K is adiabatically compressed to 40% its original volume. What is its final temperature? Homework Equations delta U = Q - W W = the integral of PdV PVgamma = constant U = 5/2nKT = 5/2nRT (diatomic, ideal gas) The Attempt at a Solution...
  38. D

    What is the final pressure of an adiabatically compressed gas in a container?

    Homework Statement a container with air (M = 29 g/mol, treated as an ideal gas). In the container, we have 2.0 L of the gas with p1 = 1.0 atm at T1 = – 50C. The gas is compressed adiabatically to a final volume of 0.5 L. What is its final pressure? Homework Equations I am really not...
  39. L

    Adiabatic Curvature - Deduce the Local Adiabatic Curvature K

    Hi, I am working on the Laughlin model of Quantum Hall Effect, which relates to the concept ' adiabatic curvature'. The paper didn't include much details, and I knew little about berry phase. Could some one please give me some idea that how is the local adiabatic curvature deduced? ( the...
  40. C

    State Function Conditions in Isothermal, adiabatic

    In an Isothermic and reversible condition why is DH=0? (D=delta) I can understand that DU=0 but DH? but why would DH not change? DH should also =0 if it was an adiabtic and irreversible condition? since DH=dq/T -> as long as there is no heat transfer DH=0? Since it's reversible would...
  41. T

    Thermodynamics problem - adiabatic process

    Homework Statement One cylinder in the diesel engine of a truck has an initial volume of 600 cm^3. Air is admitted to the cylinder at 35 C and a pressure of 1.0 atm. The piston rod then does 500 J of work to rapidly compress the air. What is the final temperature and volume? I found the final...
  42. R

    Adiabatic bulk modulus of a free electron gas at T=0

    Homework Statement Show that the adiabatic bulk modulus of a free electron gas can be given by B= \frac{2nE_{F}}{3} where n-number density E_{F} -Fermi energy Homework Equations I started with the adiabatic bulk for an ideal gas K=\gamma P where...
  43. E

    Reversible adiabatic compression

    Two moles of a diatomic gas occupies a volume of 50 L and is at a pressure 4atm. The gas then undergoes a process: a reversible adiabatic compression, so that is temperature doubles. Find both temperatures, and find the volume and the pressure after the compression process. my thoughts...
  44. E

    Thermodynamics - work in adiabatic, isothermal, isobaric

    Homework Statement 21. A quantity of an ideal gas is compressed to half its initial volume. The process may be adiabatic, isothermal, or isobaric. Rank those three processes in order of the work required of an external agent, least to greatest. A. adiabatic, isothermal, isobaric B...
  45. L

    Claculating volume in an adiabatic container

    25g of ice frozen at -15 degrees C is combined with an unknown volume of steam at 200 degress C in an adiabatic container one wall of which is an adiabatic frictionless and weightless piston. Initial pressure in the container equals constant external pressure of 1 bar. CALCULATE the volume of...
  46. N

    Solve Adiabatic Process Homework: Determine Final Volume & Heat/Energy

    Homework Statement Two moles of helium at 27 deg Celsius occupies 20 liters. The gas is expanded first at constant pressure until the volume has doubled, and then adiabatically until the temperature returns to its initial value Treat helium as an ideal monatomic gas and assume that both...
  47. R

    Finding the change in pressure and entropy of a quasistatic adiabatic process

    Homework Statement Suppose that one mole of an ideal gas expands in a quasi-static adiabatic process from P1 = 1 Pa and V1 = 1m3 to V2 = 8m3. What is the change in the pressure and the entropy of the gas? Homework Equations PV\gamma=constant The Attempt at a Solution I can't come...
  48. W

    Archived Adiabatic expansion in a steady flow question

    I an working on a problem in the text "Mechanics and Thermodynamics of Propulsion" 2e. The problem states a perfect gas with molecular weight M=20 and a specific heat ratio of Y=1.2 expands adiabatically in steady flow from a pressure of 6MPa, a temperature of 3000K, and a velocity of 200 m/s...
  49. S

    Free expansion and adiabatic process

    I hope someone in here can help me out of this problem. I know that for calculating the change in entropy of a system (\Delta S) we can use this formula : \Delta S=\intδq/T Well the problem is here, when we calculating ΔS for an adiabatic process we know Q= 0 so ΔS=0 in this process, but...
  50. A

    What's the difference between isothermal and adiabatic processes?

    What's the difference?
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