Thermodynamics Definition and 1000 Threads

  1. L

    Thermodynamics: gas expansion formula or approximation error?

    FIRST TYPE: REVERSIBLE PROCESS At the temperature of 127 ° C, 1 L of CO2 is reversibly compressed from the pressure of 380 mmHg to that of 1 atm. Calculate the heat and labor exchanged assuming the gas is ideal. Q = L = - 34.95 J CONDUCT 380 mmHg = 0.5 atm L = P1 * V1 * ln (P1 / P2) = 0.5 * 1...
  2. R

    I Irreversible Isochoric Process in a Cycle

    Consider a reversible ideal gas cycle consisting of: 1. An isochoric heat addition, 2. An isothermal expansion to the initial pressure, and 3. An isobaric compression to the initial volume. What, if any, is the difference in net work done by the gas in the cycle if the isochoric heat addition...
  3. P

    Gas effusing through hole, working out time dependence

    Consider instead a thermally insulated container of volume V with a small hole of area A, containing a gas with molecular mass m. At time t = 0, the density is ##n_0## and temperature is ##T_0##. As gas effuses out through a small hole, both density and temperature inside the container will...
  4. A

    Looking for a good introductory book on thermodynamics

    Hi, I have been studying physics again and I was looking for a good introductory book for thermodynamics. I wanted to know if there is a book in thermodynamics that would be the equivalent to "An introduction to Mechanics" by Kleppner/Kolenkow, or "Electricity and Magnetism" by Purcell? These 2...
  5. bryanso

    Understanding the Laws of Thermodynamics as described by Feynman

    Hi, there is no other topics in my adventure in Feynman Lectures that makes me so loss in thoughts (https://www.feynmanlectures.caltech.edu/I_44.html). I seem to understand every sentence. But the whole thing is completely unintelligible. Let me start by asking one fundamental question. I am...
  6. A

    Thermodynamics of a Fire Resistant Safe

    Hi, I have been researching how to protect my card collection from the unlikely event of a house fire, however there is not enough data for me to estimate whether my set up is adequate or not. If anyone could approximate anything here without knowing all the exact variables (r-values) that...
  7. J

    Thermodynamics problem relating to Chemical Potentials

    For part (a), I used this formula where where the i's represent the substance being used and mu_i^0 represents some reference potential. However, to my knowledge this simply calculates the change in chemical potential from one state to another which is not of much help in finding the relative...
  8. fluidistic

    I About divergence, gradient and thermodynamics

    At some point, in Physics (more precisely in thermodynamics), I must take the divergence of a quantity like ##\mu \vec F##. Where ##\mu## is a scalar function of possibly many different variables such as temperature (which is also a scalar), position, and even magnetic field (a vector field)...
  9. E

    Stability and concavity of the entropy function

    I am struggling to understand Callen's explanation for stability, I understand that the concavity of S(U) must be negative because otherwise we can show that this means that the temperature increases as the internal energy decreases (dT/dU<0) but I cannot understand equation (8.1) which...
  10. Will26040

    How do you approximate between the Cp of a gas and a solid?

    I have the Cp of Benzoyl peroxide (BPO) in gas form (454.39 J/molK). What approximation could I make to find the Cp of solid BPO as I cannot find this info online? thanks
  11. GranMix

    Thermodynamic meaning of molar Gibbs free energy

    I know that when it is ΔG>0 , it means there is no spontaneity, when ΔG=0 there is equilibrium, and when ΔG<0, there is spontaneity. But what happens when this is in the context of partial molar properties, when G is molar? I suppose molar ΔG is referred to a solution. Right? In that case, is...
  12. B

    Help with Thermodynamics process equations and units

    For part 1. I need to find the temperature, I rearranged the equation so that: T = pV/nR (28000000)(0.45) / (28.96)(8.314) This gives me a value of 52331.4 I am unsure where the units I have used in the equation are correct. I have used pa for pressure, or should I be using kpa? this would...
  13. J

    Is there a conflict between CPT symmetry and the 2nd law of thermodynamics?

    Naively there is a conflict between CPT symmetry being at heart of fundamental physics models like QFT, and 2nd law of thermodynamics: saying that entropy grows toward future. Is there really a conflict here - so is physics symmetric or not? How to understand it? Personally I disagree with that...
  14. LCSphysicist

    Thermodynamics and adiabatic lines -- Prove this statement

    I tried by one way, seems ok and makes sense, but i am not sure if it is valid yet. $$P_{a} = c_{a}V_{a}^{(-\gamma_{a})}$$ $$P_{b} = c_{b}V_{b}^{(-\gamma_{b})}$$ $$(Pa,va = Pb,vb)$$ $$\frac{c_{a}}{c_{b}} =\frac{[V_{b}^{-\gamma_{b}}]}{[V_{a}^{-\gamma_{a}}]} = V^{-\gamma_{b}+\gamma{a}}$$ Now this...
  15. LCSphysicist

    Thermodynamics: work done on the atmosphere by an expanding gas

    V = V(n,P) PV = nc dV = (-cn/P²)dP + (c/P)dn dW = (cn/P)dP - (c)dn This was how i tried to attack the problem, but it will end with log and probably it is wrong, any tips to fix it?
  16. WMDhamnekar

    MHB What are some questions about thermodynamics and their potential answers?

    Hello, Here are the questions with unknown answers. (These chemistry questions are other math topics.) 1) At 1 bar, the boiling point of water is 372.78 K. At this temperature and pressure, the density of liquid water is $958.66 kg/m^3$ and that of gaseous water is $0.59021 kg/m^3.$ What are...
  17. L

    Engineering Why is the first law of thermodynamics useful in developing these equations?

    why it is first law of thermodynamics useful in developing the non-flow energy equation and steady-flow energy equation. First Law Equation (FLE) = 1 1.1 Non-Flow Equation = 2 Steady-Flow Equation = 3 Specific Entrapy of Steady-Flow 4 Mass Flow 5 I understand (i think) but can't explain...
  18. B

    Engineering Steady flow energy equation in Thermodynamics

    I am looking for help on the following: a) Given the system shown in the figure below, derive the steady flow energy equation from first principle. b) Again using first principles, show how the energy equation would change for the case when the system is unsteady. I am trying to learn this...
  19. Gaby

    The first law of thermodynamics for open systems

    Please see enclosed my calculations for parts 1-3. I am stuck on the final part of of a 4 part question, any help or guidance would be very much appreciated, thanks.
  20. Amaterasu21

    I How Does Relativity of Simultaneity Clash w/Thermodynamics?

    In special relativity, observers can disagree on the order of events - if Alice thinks events A, B and C are simultaneous, Bob can think A happened before B which happened before C, and Carlos thinks C happened before B which happened before A - provided A, B and C are not causally connected, of...
  21. mcastillo356

    First law of Thermodynamics and energy conservation

    Hi PF! I don't understand the sentence: on one side says the energy is preserved, and, at the end, the total energy of the system will change if ##W## or ##Q## is added: ##\Delta{U}=Q+W##. Greetings!
  22. E

    "Where’s your second law of thermodynamics now?"

    Prof. Tong used the Liouville theorem to prove the Poincaré recurrence theorem in his notes, that given an initial point ##P## in phase space, for any neighbourhood ##D_0## of ##P## there exists a point ##P' \in D_0## that will return to ##D_0## in a finite time. To illustrate the theorem, he...
  23. Tony Hau

    Problems understanding the 2nd law of thermodynamics

    So my professor says that the implication of 2nd law of thermodynamics is that high quality energy will be degraded into low quality energy. By high quality energy he means something like coal or fuel. By low quality energy he means something like heat entering the cold resevoir in a heat...
  24. T

    Help with this thermodynamics and entropy question please

    So I've answered the first question and I got a final temp of 42.06 Celsius. Now for this second one, I don't know why I am getting it wrong: Im doing 0.215*ln(315.06/291.46) + 1*ln(315.06/319.91) But it says I am wrong. What about my process is faulty?
  25. nomadreid

    What Is the Meaning of Thermokinetics?

    Wikipedia https://en.wikipedia.org/wiki/Thermokinetics says that "thermokinetics" studies the rate of chemical decomposition, whereas a dictionary https://www.yourdictionary.com/thermokinetic gets no further than saying that it combines thermodynamics and kinetics, and a book on it...
  26. nomadreid

    I Ratio of a real value to the max theoretical value: what term to use?

    If the Summary is not clear, the following is an example translated from: https://telecombloger.ru/7335 '... air conditioning systems. For example, the efficiency of a compressor is about 85%. The remaining 15% is spent on friction, oil movement, overflows, heating, etc. The efficiency of the...
  27. M

    Types of thermodynamics processes that happen in solids or continuum medium

    What are the types of thermodynamics processes that happen in solids or continuum medium
  28. P

    Interpreting a thermodynamics formula using a picture

    I notice that ##pv=t## looks like the ideal gas law but with ##T## in units of energy. I know that ##pV = \text{constant}## means that the pressure of a gas decreases as you expand it (Boyle-Mariotte's law), explaining for instance how we breathe. I guess I could put everything in words even...
  29. Hamiltonian

    Work done by irreversible and reversible processes

    I am not able to follow the derivation of work done in a reversible and irreversible process as I don't get why the work done should be different in the two processes. a reversible process is said to be a process that occurs infinitesimally slowly and an irreversible process goes from initial to...
  30. Hamiltonian

    First law of thermodynamics and the work done on a system

    The first law of thermodynamics states that the change in the internal energy of a system equals the net heat transfer into the system minus the net work done by the system. In equation form, the first law of thermodynamics is ΔU = Q − W. in the mathematical expression of the first law of...
  31. aspodkfpo

    Dodgy solution for a thermodynamics problem?

    https://www.asi.edu.au/wp-content/uploads/2020/07/ASOE_Physics_2019-answers.pdf Question 14 B) Re: " The graph of force per area vs amount of gas will change, as the pressure is increasing due to increasing temperature, so the amount of gas in a volume at a given pressure will be decreasing...
  32. M

    Is the change in internal energy really a state function?

    Here is the figure: The answer is $$Q_A<Q_B$$ which I can show by calculation using the above equations. What's confusing to me is I thought that the change in internal energy was a state function. Which would mean since the initial and final points are the same, $$\Delta E_A=\Delta E_B$$ or by...
  33. LCSphysicist

    Thermodynamics: internal energy and pressure

    The question is simply why i can't use ∂U/∂V = -P? (
  34. bsharvy

    Energy Conservation and the Dragons (Game of Thrones)

    I thought I'd calculate how much heat was required to melt the Iron Throne, and then multiply that by the number of flame-gushes during the sack of Kings Landing, to get a total amount of energy expended. Then I'd convert that to calories and use the average number of calories per goat to...
  35. Rahulx084

    Thermodynamics: Single/Homogeneous Phase Differences

    #Can somebody please explain what is the difference between single phase and homogeneous phase in context with thermodynamics? #Also in the fundamental relations in thermodynamics like dg=vdp-sdT , it says this is applicable to homogeneous phase of constant composition. Isn't this equation...
  36. TechieDork

    Need help with calculating a Cv in PHYWE's Heat Capacity of gases

    I've conducted this experiment yesterday. The main goal of this experiment is to find a gas constant R and compare it with its theoretical counterpart but I get stuck in calculating a Cv so I tried to find out what's wrong with my calculations by trying to calculate a Cv from the given data...
  37. Traced

    Chemistry Thermodynamics: The molar enthelpy of a solution

    My answer is -0.40 kJ/mol. I'm having trouble understanding why the molar enthalpy of the solution is a negative number. Wouldn't this mean that the solution is losing energy? If the temperature of the water heats up from 20 degrees Celsius to 36 degrees Celsius shouldn't the final answer be...
  38. P

    Heat engine that uses a rubber band (Thermodynamics)

    Nota that the path a to b is isothermal since J is proportional to L, then we can find the value of T_a and T_b using the equation of state and the figure. We have, \begin{equation} J_0=\alpha L_0T_b \end{equation} or \begin{equation} T_b=T_a=\frac{J_0}{\alpha L_0}=T_0 \end{equation} Also, by...
  39. Ron19932017

    Euler's equation of thermodynamics in free expansion (Joule expansion)

    Hi everyone, I am confused when I apply Euler's equation on the free expansion of an ideal gas. Consider a free expansion (expansion of gas in vaccum) where the volume is doubled (V->2V) The classical free expansion of an ideal gas results in increase in entropy by an amount of nR ln(2), a...
  40. TytoAlba95

    Chemistry Thermodynamics: Reduction Potential question

    The answer key says the correct option should be a, but I think it should be b. Because Y has a reduction potential same as the element B. An element is a good reducing agent only if its reduction potential is negative or less positive.
  41. M

    Is the Second Law of Thermodynamics Falsifiable?

    My question relates to whether the 2nd law of thermodynamics is a an empirical or mathematical law. If we can reason purely from the laws of statistics that entropy can only increase, then the 2nd law of thermodynamics cannot be falsifiable and therefore shouldn't be considered a scientific...
  42. B

    Clausius clapeyron and heat capacity

  43. N

    Thermodynamics: phase change and latent heat problem

    The second question is where I'm lost. The answer to the first question is 5.39 grams. The second is 10.3 grams. Until I saw the answer I was setting the equation up as if some of the original steam had condensed. But it appears that some of the original water changed into steam. Is it necessary...
  44. T

    What is the significance of the grand partition function in an Einstein solid?

    $$Q_{(\alpha, \beta)} = \sum_{N=0}^{\infty} e^{\alpha N} Z_{N}(\alpha, \beta) \hspace{1cm} (3.127)$$ Where ##Q## is the grand partition function, ##Z_N## is the canonical partition function and: $$\beta = \frac{1}{kT} \hspace{1cm} \alpha = \frac{\mu}{kT} \hspace{1cm} (3.128)$$ In the case of an...
  45. vjrajsingh

    Non-equilibrium thermodynamics

    Biological systems act as dissipative structures and obey the universal laws of thermodynamics in spite of being open structures as they follow non-equilibrium thermodynamics. In accordance with the second law, entropy generation occurs. Is it possible to limit the entropy generation in a...
  46. A

    What is the -1st law of thermodynamics?

    The so called -1st (Minus First) law of thermodynamics, I believe states that information cannot be destroyed, or something along those lines. Does anyone know where I can read more about it? I think I've heard Dr. Leonard Susskind talk about it but it's been hard to find the video or any other...
  47. J

    Ipho 1987, thermodynamics problem: Moist air ascending over a mountain range

    I'm struggling with explanation of part 3. I don't know why they are using adiabatic equation while the gas is constantly heated by condensating vapour. While we are deriving adiabatic equation we use the fact, that there is no additional heat put into the system. Thank you in advance.
  48. J

    Exploring Entropy: A Systems Engineering Perspective

    As a systems engineer I have thought a lot about entropy in trying to get a better intuitive sense for what it is, at a more macro level than it is usually discussed. I have some ideas and am looking for a forum to present and explore them with others. I wish to discuss more from an...
  49. Amaterasu21

    At what size is kinetic energy no longer related to temperature?

    Hi all, I've read so many times that "temperature is a measure of the average kinetic energy of the molecules in a substance," or sometimes "particles" to encompass atoms and ions too. But how big can "molecules/particles" be before their kinetic energy is no longer relevant to temperature? If...
  50. L

    Teaching Thermodynamics with minimal math

    Thermodynamics is an interesting subject but all too often students think of it as solving math problems. And indeed most of the problem solving involves calculations which can be quite in-depth, requiring knowledge of calculus. I have been looking for ways to deliver thermodynamics principles...
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