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. O

    How are the adiabatic and isobaric expansions of an ideal gas related?

    I'm deriving this formula for the adiabatic expansion of an ideal gas. PV^{\gamma} = Constant_2 there are 3 ways to expand to end up at same internal energy dU. 1. this is the direct adiabatic expansion from T1 to T3 dU_{systA} = -dW_{systA} = -P_{systA} dV where P_{systA} is a function...
  2. Z

    Thermodynamics: adiabatic processes

    Homework Statement A multicylinder engine in an airplane operating at 2500 rev/min takes in energy 7.89 x 10^3 J and exhausts 4.58 x 10^3 J for each revolution of the crankshaft. (a) How many litres of fuel does it consume in 1.00 h of operation if the heat of combustion is 4.02 x 10^7 J/L ...
  3. C

    Explaining Adiabatic Cooling: What Is It & Why Does It Happen?

    I understand that adiabatic cooling is the reason as to why, a valve releasing compressed air from a tire, would become cold. But I'm having a hard time grasping why this actually happens. I've been searching online, and I can't seem to find the type of simplified answer I'm looking for...
  4. S

    Andrew mason ideal gas law and adiabatic expansion problem

    Q1. ADIABATIC FREE EXPANSION(unrestricted and free) in vacuum gas a volume of gas is released expected expansion proceeds withouut change in internal energy therefore temperature is contant (joule's law) . there is no pressure acting on this system threfore no work is done...
  5. P

    Adiabatic compression in a diesel engine

    Homework Statement In a diesel engine, atmospheric air is quickly compressed to about 1/20 of its original volume. Estimate the temperature of the air after compression , and explain why a Diesel engine does not require spark plugs. Homework Equations f/2*ln(T_f/T_i)=-ln(V_f/V_i) The...
  6. S

    Adiabatic Processes for an Ideal Gas

    Homework Statement The problem is derive the adiabatic processes for an ideal gas going through a point (v,p) on the p-V plane. Also, in terms of p,T and v,T. Draw the curves. Homework Equations First Law of Thermo Properties of an Ideal Gas Properties of Adiabatic Processes...
  7. C

    Delta U, H, S for an Irreversible Adiabatic process.

    Suppose that one mole of a monatomic perfect gas at 27°C and 1.00 atm pressure is expanded adiabatically (i.e. no heat transfer, so that the temperature must fall) in two different ways: (a) reversibly, to a final pressure of 0.5 atm, and (b) against a constant external pressure of 0.5 atm...
  8. K

    Exploring Entropy of Adiabatic Mixing of Two Gases

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  9. Y

    Sudden Approximation and Adiabatic theorem

    I am reading quantum mechanics (Messiah) now. And I get confused about the condition for the validity of the sudden approximation in CH. XVII. The author use perturbation theory to derive the result T<<\hbar/\delta \overline{H} ,when the Hamiltonian change over time T. The condition tells...
  10. P

    Adiabatic demagnetization of paramagnetic

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  11. S

    Calculate Air Temperature During Compression - TurboFast

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  12. J

    Adiabatic Spin Manipulation in EPR Experiment

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  13. J

    Adiabatic Process and Heat Absorption

    Homework Statement An adiabatic process is performed on 15 moles of an ideal gas. the initial temperature is 320 K and the initial volume is 0.80m^3. the final volume is 0.40m^3. the adiabatic constant for the gas is 1.44 the heat absorbed by the gas in kJ is closest to a. 0 b.+54 c.-14...
  14. J

    Adiabatic Process: Final Temp & Heat Absorbed Calculation

    Homework Statement twenty moles of a monatomic ideal gas (lambda=5/3) undergo an adiabatic process the initial pressure is 400kpa and the initial temperature is 450K. The final temperature of the gas is 320K. The heat absorbed by the gas in kJ is closest to? a.0 b.+54 c.+32 d.-54 e.-32...
  15. D

    Isobaric, Isochoric, Isothermal, and Adiabatic Processes

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  16. N

    What is an Adiabatic Expansion Coefficient?

    Hi, Can anyone tell me what this means? I'm trying to find the adiabatic expansion coefficient in order to use this air compressor calculator. http://www.engineeringtoolbox.com/horsepower-compressed-air-d_1363.html These are the variables I have at the moment... Number of stages-...
  17. S

    Thermodynamics - This time it really is adiabatic

    Homework Statement 14 grams of Nitrogen at 20 degrees Celsius in 1 atmosphere of pressure is compressed to a pressure of 20 atmospheres. What is its final temperature and what is the work done on the gas if the process is adiabatic? Obtain the compression ratio (i.e. Vmax/Vmin). How much...
  18. L

    Entropy of an adiabatic process

    Homework Statement A sample of 1.00 mol of an ideal gas at 300 K and 101325 Pa is expanded adiabatically in two ways: a) reversibly to .5 atm and b) against a constant external pressure of .5 atm. Determine the values of q, w, \DeltaU, \DeltaH, \DeltaS, \DeltaSsurr, and \DeltaStot for each...
  19. P

    Adiabatic Expansion: Final Temperature?

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  20. S

    Adiabatic Expansion Homework: q,w,ΔU,ΔT,ΔH

    Homework Statement A sample of 2.5 mol O2 (Cp,m = 29.355 J K-1 mol-1) is originally confined in 23 dm3 at 270 K and then undergoes adiabatic expansion against a constant pressure of 600 Torr until the volume has increased by a factor of 3.0. Calculate q, w, ΔU, ΔT, and ΔH. (The final...
  21. F

    Calculating Pressure & Temp for NH3 Quasistatic Adiabatic Expansion

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  22. T

    Calculating Ideal Gas Temperature in an Insulated Tank | Cp and Cv Known

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  23. J

    What is the Error in My Derivation of the Dry Adiabatic Lapse Rate?

    I am aware of the derivation for the dry adiabatic lapse rate using the enthalpy approach: ncpdT+VdP=0, but I can't seem to spot the error in my own derivation. If anyone sees it, I would be especially grateful. dU=\deltaQ-\deltaW ncvdT=0 - PdV \frac{dT}{dV}=-\frac{P}{nc_{v}}...
  24. J

    Adiabatic steady state flow in a nozzle

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  25. J

    Help to understand fast adiabatic expansion

    Hi, I am going through a book on thermal physics (specifically on a section on the 2nd Law) It talks about an extremely fast adiabatic expression (as a gas in one flask separated by a valve to another flask in vacuum and then the valve is opened). What I fail to understand is that...
  26. T

    Adiabatic Hot-Air Balloon Rising Question

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  27. G

    Adiabatic expansion of a balloon

    Homework Statement A flexible balloon contains 0.375 mol of hydrogen sulfide gas H2S. Initially the balloon of H2S has a volume of 6750 cm^3 and a temperature of 29.0 C. The H2S first expands isobarically until the volume doubles. Then it expands adiabatically until the temperature returns...
  28. M

    Adiabatic Slope: Ideal Gas Equation

    Homework Statement The slope of an adiabatic curve will be equal to r times the slope of an isothermal curve only when we use the ideal gas equation Homework Equations The Attempt at a Solution Adibatic process, P(V)^g = constant Differentiating w.r.t V...
  29. L

    SLI webinar: Solving the Adiabatic Balloon Problem

    I need to solve this problem. A big balloon with volume V1 = 2.00 * 10^3 m^3 contains helium at 15 degrees celcius and 1 atm. The balloon now rises from the ground to a height 'h' where the pressure is 0.900 atm. The process is adiabatic: a) find the volume at height h b) find the...
  30. A

    Reversible adiabatic expansion/compression equal to zero

    So, I am looking a question about adiabatic expansions and the associated entropy changed. Why exactly is the change in entropy for a reversible adiabatic expansion/compression equal to zero? The book says its because there is no heat transfer, but for irreversible adiabatic processes, there...
  31. N

    Adiabatic Compression Temperatures

    Hi, When a gas is compressed, its temperature increases. But what is the formula to calculate this rise? Could you please explain the formula too. This isn't homework btw! Thanks!
  32. T

    What is the work done during an adiabatic process?

    Homework Statement During an adiabatic process, the temperature of 5.50 moles of a monatomic idea gas drops from 495 C to 215 C. For this gas, find (a) the work it does, (b) the heat it exchanges with its surroundings, and (c) the change in its internal energy Homework Equations I know...
  33. J

    Proof that PV^gamma is constant in a reversable adiabatic condition.

    I've been working on this proof, and I just can't get it backwards or forwards, so I must be going about it wrong or missing something. I'm on a re-do for the homework, because my first attempt was completely wrong, so here I go with the second. Any guidance would be appreciated. Homework...
  34. N

    Thermodynamics, adiabatic process

    Homework Statement I have the equation for the internal energy: U = (f/2) * N * k * T, where f is the degrees of freedom, N is the number of molecules, k is Bolzmann's constant and T is the temperature in Kelvin. This can be written as U = (f/2)*p*V using the ideal gas law...
  35. nicksauce

    How Is Temperature Related to Pressure in Adiabatic Expansion of an Ideal Gas?

    Homework Statement Show that when an ideal gas expands adiabatically, the temperature and pressure are related by the differential equation: \frac{dT}{dP} = \frac{2T}{5P} Homework Equations Ideal gas law The Attempt at a Solution PV = nkT T = \frac{PV}{nk} \frac{dT}{dP} =...
  36. F

    Adiabatic & Quasistatic Expansion of Photon & Fermion Gases

    Homework Statement 1.Show that PV^Y is a constant for adiabatic,quassistatic expansion of a photongas and determine Y 2. Show the same for full degenerate gas of fermions at T=0 Homework Equations The Attempt at a Solution Plz help thx
  37. M

    Heat and adiabatic processes perhaps

    You have two cups, one with m1 = 2.73 kg of water at t1 = 42.32oC and the other with m2 = 1.88 kg at t2 = 21.34oC. You mix the two in an insulated thermos. What is the final temperature of the water? I'm pretty sure that this is supposed to be an adiabatic process, because you are trying to...
  38. I

    Rapid adiabatic compression - puzzle

    I want to know if in rapid adiabatic compression of a gas, is work done by gas on surrounding (atmosphere) numerically same as work done by surrounding on the gas. Please tell if there exists some solid proof of the answers you guys are giving.
  39. I

    Work done in irreversible adiabatic process

    This question came some time back in Stony Brooks exam. I have the solution also. But i am having some conceptual doubts. Can someone help me please. The question is: Consider ‘n’ moles of an ideal monoatomic gas placed in a vertical cylinder. The top of the cylinder is closed by a piston...
  40. M

    Adiabatic Process Homework: 2 moles of CO Gas

    Homework Statement 2 moles of Carbon monoxide gas start at a pressure of 1.2 atm and a volume of 30 litres. The gas is then compressed adiabatically to 1/3 this volume. Assume that the gas may be treated as ideal. What is the change in the internal energy of the gas? Does the internal energy...
  41. T

    Calculating work in Adiabatic compressions

    Hi, I'm thinking about how to derive an expression for the final temperature (call it T2) and the work done (call it W) in an adiabatic compression, when you only know the initial and final pressures (call them P1 and P2), and the initial temperature (call it T1). I'm not sure about my...
  42. L

    Irreversible adiabatic reaction

    Hey everyone =) This is my first post here but I've been lurking for a while. Anyway, so i am taking this physical chemistry class and I can't seem to solve this problem. I think it is still a physics problem. Anyway, it goes like this: small amount of moles of steam (.83 moles) @ 100...
  43. D

    Is there any way for the entropy to increase in an closed adiabatic sy

    1) Is there any way for the entropy to increase in an closed adiabatic syatem? 2) what are the mechanisms of entropy generation within a closed thermodynamic system? Thank you
  44. M

    Adiabatic expansion of CO2 - rate of cooling

    Hi Physics forum, I have a pipe which is of length L, inner diameter D. It is packed with CO2 at pressure P (assume it's still a gas with none of this funny supercritical business!) and temperature T. The density of the CO2 is rho and the joule-kelvin coefficient is mu. the pipe is initially...
  45. A

    Adiabatic expansion of a monatomic gas

    Homework Statement The molar energy of a monatomic gas which obeys van der Waals' equation is given by E = (3/2)RT - a/V V volume, T temperature, a is a constant. Initially you have T1 at V1, and the gas expands adiabatically in a vacuum so that you have V2. What is T2? Homework...
  46. S

    Adiabatic Cooling: Q&A for Dummies

    Hi, I don't fully understand this thing. I've read it on wiki, but it just doesn't get through. Perhaps I am a dumbass. I've 3 questions that hopefully will help clear it up. 1) How do you stop adiabatic cooling? 2) In a closed and insulated system where there is a compressed gas...
  47. S

    Explaining Adiabatic Process taking Van Der Waals Equations?

    To Forum Physicists / Administrators... Equations for an ideal gas undergoing an adiabatic process are 3 viz 1) P(v^g)=const 2)T(V^(g-1)) =constant and 3)T(P^((1-g)/g))= constant where g=specific heat for const pressure/specific heat for const volume.These equations suits the Ideal gas...
  48. I

    How Does Adiabatic Compression Affect Entropy and Temperature in Nitrogen Gas?

    Homework Statement A sample of 5 moles of nitrogen gas (γ = 1.40) occupies a volume of 3.00 × 10^−2 m3 at a pressure of 2.00 × 10^5 Pa and temperature of 280 K. The sample is adiabatically compressed to half its original volume. Nitrogen behaves as an ideal gas under these conditions...
  49. G

    Adiabatic Compression: Understanding Internal Energy and Work in Gases

    If a gas is adiabatically compressed and the calculated change in internal energy is 1600J, is the WORK done on the gas also 1600J??
  50. G

    Change in Entropy and adiabatic process

    If a process is adiabatic and reversible, such as a gas in a tube that has been compressed, is it true to say that there is no change in entropy from the gas being uncompressed to being compressed? If not, why not?
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