What is Thermodynamics: Definition and 1000 Discussions

Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, radiation, and physical properties of matter. The behavior of these quantities is governed by the four laws of thermodynamics which convey a quantitative description using measurable macroscopic physical quantities, but may be explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a wide variety of topics in science and engineering, especially physical chemistry, biochemistry, chemical engineering and mechanical engineering, but also in other complex fields such as meteorology.
Historically, thermodynamics developed out of a desire to increase the efficiency of early steam engines, particularly through the work of French physicist Nicolas Léonard Sadi Carnot (1824) who believed that engine efficiency was the key that could help France win the Napoleonic Wars. Scots-Irish physicist Lord Kelvin was the first to formulate a concise definition of thermodynamics in 1854 which stated, "Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, and the relation of heat to electrical agency."
The initial application of thermodynamics to mechanical heat engines was quickly extended to the study of chemical compounds and chemical reactions. Chemical thermodynamics studies the nature of the role of entropy in the process of chemical reactions and has provided the bulk of expansion and knowledge of the field. Other formulations of thermodynamics emerged. Statistical thermodynamics, or statistical mechanics, concerns itself with statistical predictions of the collective motion of particles from their microscopic behavior. In 1909, Constantin Carathéodory presented a purely mathematical approach in an axiomatic formulation, a description often referred to as geometrical thermodynamics.

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  1. B

    Heat distribution in a piece of glass receiving protons

    First of all, I didn't know whether to pick this subforum or the engineering/compsci one, I understand this might need to be moved to a more appropriate subforum. The general approach is fairly obvious, use implicit method to construct the tridiagonal matrix for Thomas method and solve. However...
  2. J

    The Physics of cooking breakfast (basic thermodynamics)

    I eat eggs, ham, peppers, and a pancake for breakfast. I cook the ham and peppers at the same time. For purposes of this question, I have the eggs and the pancake figured out. Given a gas stove, a small, nonstick aluminum frying pan (with lid) and corn oil; If my goals are (in order of...
  3. Haozi02133

    I need a help on thermodynamics physics relating to Metallic Hydrogen

  4. A

    Gas - cylinder - piston problem

    Summary:: Seeking explanation to classical gas - cylinder - piston problem, not the solution. Problem 1.15 from 7th edition of Introduction to Chemical Engineering Thermodynamics by Smith, Van nes and Abbot) Classical problem, given: - gas in a confined cylinder - piston with weight is placed...
  5. T

    Thermodynamics -- Calculations for heating water up

    A thermal flask with water of temperature 90c is placed out in room temperature 20c, sealed. How long before it reaches 55c? outer radius and height: 5cm, 25cm volume of water is 1litre. R = 0.5 Km2/W using this equation to solve it combining these two and integrating with respect to T...
  6. Y

    Why use c_p and not c_v as specific heat - Thermodynamics

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  7. I

    Question about thermal physics -- Ice cubes melting in water

    First, I calculated the heat required for the ice to melt: Q=mLf Q=0.150×330 Q=49.5 J Then, I calculated the final temperature of the water by forming the following equation: Q=mcΔT −49.5=(0.15+0.35)×4200×(Tf −80) Tf=80.0 degrees Celcius But the answer says 32 degrees Celsius.
  8. H

    I Thermodynamics Differentiating logarithms

    <mentor: change title> In thermodynamics, there is a function which, for the three variables x, y, and z, can be given as ##G = xG_x+yG_y+zG_z + N[x\ln(x) + y\ln(y)+ z\ln(z)]+E(x,y,z)## where G_x, G_y, G_z, and N are some constants and E is some arbitrarily complicated term. There is a...
  9. RoisinCleary

    Impossible thermodynamics Q :(((

  10. A

    Conceptual thermodynamics problem about ammonia executing a Carnot cycle

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  11. A

    Conceptual thermodynamics question regarding specific heat ratio

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  12. jackdale

    The Second Law of Thermodynamics and the Stefan-Boltzmann Law

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  13. P

    Thermodynamics Problem: Reversible and Irreversible Processes

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  14. VVS2000

    Fundamental equation (thermodynamics) from Euler's equation

    by substituting all values in the euler equation you get most of the terms in the fundamental equation but not (N/No)^-(c+1) How do you get this term?
  15. M

    Thermodynamics Problem: Cylinder-Piston System with Friction

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  16. S

    High Energy Introductory notes on AdS/CFT or black hole thermodynamics

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  17. B

    Thermodynamics: calculate thermodynamic derivative from data?

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  18. Sokolov

    Integration of inexact differentials in Thermodynamics

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  19. Y

    Engineering Find out the percent exergy loss

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  20. WateryFungi

    Engineering Thermodynamics - Control Volumes find final temperature

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  21. A

    Thermodynamics energy balance for control volume

    Why is energy balance for a control volume dE/dt = dQ/dt-dW/dt-dm/dt(ΔH+ΔKE+ΔPE) 0 = dQ/dt-dW/dt-dm/dt(ΔH+ΔKE+ΔPE) whereas for other systems it is ΔE =Q-W-(ΔU+ΔKE+ΔPE) 0 = Q-W-(ΔU+ΔKE+ΔPE) with enthalpy, h = u +pv, replaced by only the internal energy? How is the pv term accounted for...
  22. M

    Engineering Thermodynamics - Second Law: 2 Heat Engines Connected Between 3 Metal Blocks

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  23. M

    Thermodynamics Problem: Heat Engine Between Two Blocks

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  24. obstinatus

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  25. C

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  26. Anon_Miner

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  27. Robert DeVries

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  28. Z

    Thermodynamics: find the change of internal energy, the work and Q

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  29. Rahulx084

    Thermodynamics -- Temperature of a Heat Source?

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  30. T

    1st Law of thermodynamics : moving reference frame

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  31. E

    Confused about use of external vs internal pressure in thermodynamics

    I've learned that ##W = -\int{P_{ext} dV}##, and only during a reversible/quasi-static process where ##P_{int} = P_{ext}## can we write the work done on the gas in terms of the internal pressure (and consequently use ##PV=nRT## etc. which apply to the internal gas). However, a lot of sources...
  32. E

    Ignoring the acceleration of a piston in thermodynamics

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  33. C

    B Irreversible expansion of gas against gas

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  34. T

    Adiabatic approximation in the derivation of the speed of sound

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  35. F

    Temperatures of the hot source and cold sink in a heat engine

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  36. H

    Thermodynamics: Why does salt lower the melting point of ice?

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  37. C

    Thermodynamics - Change in temperature for heated slabs of steel

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  38. Stephen Bulking

    Thermodynamics problem involving engine efficiency

    Q2: An engine has power of 26.5 kW, needs 9 kg coal during an hour for energy. The heat capacity of coal is 7800 cal/g. Define the engine’s efficiency. Qh= mcΔT = 9000x7800xΔT ( stuck) P=26.5kW(is this the power output of the engine in an hour?) If only I could find ΔT, thenI would be able to...
  39. WhiteWolf98

    Finding Isentropic Enthelpy, knowing Isentropic Entropy

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  40. A

    Does classical statistical physics predict newer things vs. thermodynamics?

    I'm wondering if the passage from a classical thermodynamic theory, i.e. which does not resort to an atomistic theory and methods of probability and statistics, to classical (i.e. non-quantum) statistical mechanics, led to new discoveries and especially if it was able to explain properties of...
  41. Physics345

    Entropy and the Laws of Thermodynamics

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  42. C

    Is Specific impulse indicative of performance as a gun propellant?

    Black powder has specific impulse of around 80s, while rocket candy has up to 130s of specific impulse. Does that mean I could replace the propellant in a BP cartridge with 80/130 of the weight in rocket candy and obtain the same performance in an idealized gun? (as in without considering...
  43. D

    Entropy and the second law of thermodynamics

  44. WhiteWolf98

    Clausius-Clapeyron equation to estimate sublimation pressure of water

    Before this question, the questions were about the Clapeyron equation, and how to estimate ##\Delta s##. I'm completely put off by this question however, and don't know where to start. I've found that the triple point of water is at ##0.01°C##, and there is indeed data in the table for...
  45. K

    Gibbs' theorem and partial molar volume

    In the chemical engineering text of Smith, VanNess, and Abbott, there is a section on partial molar volume. It states that Gibbs theorem applies to any partial molar property with the exception of volume. Why is volume different? In other words, when evaluating the partial molar volume of a...
  46. P

    Temperature and non-equilbrium thermodynamics

    Suppose we have a body that isn't a black body, but has an arbitrary emission spectrum. In the general case, can the radiation from this body be characterized as having a temperature, and if so, how? If not, what conditions are needed to make the concept of temperature meaningful in this case?
  47. Romantic_night

    Thermodynamics question about glass (quartz)

  48. R

    Question about the first law of thermodynamics

    In thermodynamics, the internal energy (U) is the function of the volume (V) and temperature (T), U = U (T). Therefore, according to the mathematics, dU = π dV + Cv dT, where π is internal pressure and Cv is the constant volume heat capacity. Meanwhile, according to the 1st law, dU = δ w + δq...
  49. yecko

    Why is the change in entropy of a heat pump in one cycle equal to zero?

    as it is not ideal, total change of entropy > 0 entropy loss of hot reservoir > entropy gain of cold reservoir why would the change in entropy of the heat pump in one cycle equals to zero? thank you
  50. Sai Maurice

    Temperature change brought about by radiation

    I tried modeling the problem quite a few ways. one was to say that the difference between the heat emitted by the room and the heat emitted by the bulbs would equal the heat absorbed by the room, and that could allow us to calculate temperature. This did not work. I'd appreciate your help
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