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. Javier0289

    Thermodynamics - How to find an "adiabat"?

    I tried this... but I'm not sure if I'm doing it right or maybe there's a simpler way. Thanks for your time or help :) The fundamental relation is: $${S \over R} = {UV \over N} - {N^3 \over UV}$$ but I used $$s=S/N, u=U/N, v=V/N$$ to obtain $${s \over R} = uv - {1 \over uv}$$ then I did...
  2. A

    AIK, this is the best I can do for you.

    Carnot's postulate: one cannot build an engine whose sole effect is to transfer heat from a cold body to a hot body. How granted this postulate can I prove that no engine beats Carnot's engine? From this postulate, I can conclude that work must be done from the surroundings and that Carnot's...
  3. Baibhab Bose

    Phase transition between two phases with different Cv

    I actually can't figure out what kind of phase transition it is and how to proceed through..!
  4. S

    How to calculate the transition temperature in this problem?

    Summary: The transition Sn(s, gray) ⇌ Sn(s, white) is in equilibrium at 18°C and 1 atm pressure. If ΔS = 8.811K mol for the transition at 18°C and if the densities are 5.75 g/cm3 for gray tin and 7.28 g/cm3 for white tin, calculate the transition temperature under 100 atm pressure The...
  5. Dan13

    How Does Expansion Affect Internal Energy in a Monatomic Ideal Gas?

    Problem Statement: A monatomic ideal gas expands from 100cm³ to 200cm³ at a constant pressure of 1.0 × 10⁵ Pa. Find the change in the internal energy of the gas. Relevant Equations: Included in my attempt at a solution
  6. alexmahone

    Textbook containing the Rankine cycle (Thermodynamics)

    I'm taking an online course that covers the Rankine power cycle, that, unfortunately, isn't mentioned in any of my textbooks. Do you guys have a textbook that covers this cycle? Thanks
  7. A

    Does the First Law of Thermodynamics Allow for Heat Generation During Stirring?

    Consider a system composed of a gas+stirrer at state 1, Work is done on the system by a rotating shaft, the stirrer activates high speed generating a significant amount of heat. The system is undergoing a process because the set of measurable properties to define its state are changing, If I...
  8. QuasarBoy543298

    Question about the 0th law of thermodynamics

    assume I have 3 systems a,b and c. the equilibrium between a and c can be described by the equality PcVc = f(A1,..., An) and the same for b and c - PcVc = g(B1,...,Bk). why does the equality g(B1,..., Bk) = f(A1,..., An) describes an equilibrium between A and B? the 0th law states that if A and...
  9. S

    Changing the Air Temperature with a hair dryer

    Hi, so I found this on another old "AP" High School Finals Exam. I think I may be super lost. Because the only way that I can think about is KE = 3/2kT. And then that the difference of the Kinetic Energy of the air Particles is the Q supplied by the heater inside the air dryer. So ## \frac...
  10. L

    How do atoms affect thermodynamics?

    There was a time when they didn't believe in atoms. But thermodynamics and temperature still existed and applied. What are the ways that atoms can influence thermodynamics? I can only think of one now where the temperature of the nuclear warhead suddenly increased million folds due to the chain...
  11. P

    I The laws of thermodynamics and the Universe

    How would the first and second laws of thermodynamics apply to the creation and existence of the universe? I'm not a physicist (and unfortunately, do not remember a lot that I learned in Physics class in school and college about Thermodynamics). I did some searching and I have come across an...
  12. S

    Thermodynamics (sort of) for a non engineer

    I have a 30 by 30 shop with insulation and 10 foot ceilings. I have been reading about geothermal and it got me curious. If I were to bury 1 inch PVC type pipe and ran water and radiator fluid or water and some type of alcohol like windshield washer fluid is there a formula to determine the...
  13. babaliaris

    Thermodynamics: I can't solve this simple entropy exercise....

    The text says: "Steel bullet of 25kg with a Temperature of 400 Celsius, is being dropped on the bottom of an oil liquid of 100kg at a temperature of 100 Celsius. The system is isolated. Calculate a) The change of entropy of the bullet, b) the change of entropy of the oil, c) the total change of...
  14. M

    Year 11 Physics depth study (Waves and thermodynamics)

    I don't know how to make the practical or what practical I can conduct that would test the question we have been given.
  15. JD_PM

    Heat engine undergoing an elliptical cycle

    An ideal diatomic gas undergoes an elliptic cyclic process characterized by the following points in a ##PV## diagram: $$(3/2P_1, V1)$$ $$(2P_1, (V1+V2)/2)$$ $$(3/2P_1, V2)$$ $$(P_1, (V1+V2)/2)$$This system is used as a heat engine (converting the added heat into mechanical work). Evaluate the...
  16. wasmaro

    [Thermodynamics] How much mass is extracted to decrease pressure

    I have a feeling some integration will be required, I just want to see if anyone know of a quick way.
  17. Parzeevahl

    Entropy change for water in contact with a reservoir

    Problem Statement: 1 kg of water at 273 K is brought into contact with a heat reservoir at 373 K. When the water has reached 373 K, what is the entropy change of the water, of the heat reservoir, and of the universe? Relevant Equations: dS=Cp*(dT/T)-nR*(dP/P) dS=Cv*(dT/T)+nR*(dV/V) I am...
  18. T

    Relativity Any good references on the thermodynamics of black holes?

    So, for the end of this semester's introductory couse in General Relativity (undergrad) I have to do a project on "The analogy between the mechanical laws on a black hole and the laws of thermodynamics". I couldn't find much (at least on my own) about this particular topic in my university's...
  19. jambaugh

    What Thermodynamics and Entropy Means

    Continue reading...
  20. Rahulx084

    Questions about the Point Function (Thermodynamics)

    We know from first law of thermodynamics for a closed system that ##dE##=##\delta Q## -##\delta W## , my question is that for a closed adiabatic system net heat transfer =0 this mean net change in energy = work done , does that mean for an adiabatic system work done is a point function as...
  21. H

    I Calculate the number of states for a particle in a box

    The multiplicity of states for a particle in a box is proportional to the product of the volume of the box and the surface area of momentum space. $$ \Omega = V_{volume}V_{momentum}$$ The surface area in momentum space is given by the equation: $$p^{2}_{x}+ {p}^{2}_{y}+{p}^{2}_{z} =...
  22. Ronemberg Junior

    The second law of the thermodynamics and philosophy

    The second law of thermodynamics tells us that the amount of useful energy in an isolated system tends to decrease. Does this imply that mankind will reach a point where it cannot longer use any kind of energy? If so, do we have an estimate of how long it will be necessary for to haven't useful...
  23. E

    B Black holes and the first law of thermodynamics

    The first law of thermodynamics states that matter can only be transferred from one state to another, and cannot be truly destroyed. What happens to matter consumed by a black hole? What happens to it and where does it go? Does the first law still hold true?
  24. C

    Help with Thermodynamics assignment

    Hi, I am doing a level 3 engineering diploma, myself and the rest of my class are struggling to answer most of the questions on the attached assignment paper particularly questions 2, 4, and 6 and 7. I have worked out q1 to be 7.3 icebergs per year needed and 7.3 x 10^3 volume needed. Most of...
  25. R

    Video lectures or online course in thermodynamics

    Hello, I am beginning a course in thermodynamics in which we will be using the textbook "Fundamentals of Engineering Thermodynamics" (Moran, Shapiro Et al.). Does anyone know of a video series which covers similar topics as in textbook? I have the textbook, I am just looking for a supplement...
  26. J

    Equating two formulas for root-mean-square velocity

    (a) My question : Are all the formulas correct? If so I can write ##v_{rms}## in form (2) and compare that result with the other velocities to get the answer (rms > average > most probable)
  27. SeeSharp

    Construction Project Idea involving Thermodynamics, Robotics and AI?

    Hello, Just like the title suggests, I am looking for DIY project ideas, that involves Thermodynamics, Robotics, and Artificial Intelligent. I would like to use C++ and Simulink. And I am able to purchase components, e.g. Raspberry Pi and electrical components. If you have any ideas for a...
  28. N

    Polytropic Process equation [Thermodynamics]

    Hello there, So yesterday my thermodynamics professor did some black magic and transformed our beloved equation (1/(1-n))*(p1v1-p2v2) into (n/(n-1))*(p1v1-p2v2), but i didnt understand why he did it and how (he is too fast for my writing). Does anyone know how he did it, are there any...
  29. J

    Simple clarification regarding the sign convention for work

    Precursor : Sign conventions regarding Work by the system/on the system may even vary among Physics textbooks and among Chemistry textbooks and as a rule of thumb it is better to clearly mark out the convention used by the text being referred to specifically and remain consistent with it...
  30. J

    Definition of Heat and the First Law of Thermodynamics (discrepancy?)

    Zemansky defines Heat as : When a closed system whose surroundings are at a different temperature and on which diathermic work may be done undergoes a process, then the energy transferred by non mechanical means, equal to the difference between the change in internal energy and the diathermic...
  31. Irene Jin

    Pressure of Inert Gas in kN/m^2: 167.82 | Well-Type Manometer

    A well-type mercury manometer has a well of 0.02m^2 area and a tube of 40mm^2 area. The liquid has a density of 13,534 kg/m^3.Given that the tube is open to the atmosphere and the well is connected to the inert gas manometer was to measure: Calculate the pressure of the inert gas in kN/m^2 if...
  32. R

    Thermodynamics and ideal gas law concepts

    I'm having trouble wrapping my head around some thermodynamics and ideal gas law concepts. I don't have a specific textbook question but Just a concept I'm having trouble with. What I'm struggling with is understanding some of the relations between pressure, volume and temperature...
  33. QuasarBoy543298

    The second law of thermodynamics -- What does "from cold to hot" mean?

    in Clausius formulation, what does the phrase "from cold to hot" means? I can understand it intuitively but in the language of the zero and first laws, we have not defined a temperature scale, only equivalence classes of systems that will be in equilibrium with each other (systems with the same...
  34. S

    Review of modern non-equilibrium thermodynamics theories

    Looking for thorough serious comparative review of modern generalisations of classical non-equilibrium thermodynamics of continua. I have heard about several such generalisations: 1) rational mechanics by Truesdell, Coleman, Noll. 2) extended thermodynamics by Müller (and Ruggeri). 3) the...
  35. Quentin_Phys

    Relationship between the Volume of a balloon and the time it takes to deflate

    I would like to ask a question on whether there is a proportionality between volume of a balloon, and the time it takes to deflate. I have conducted several balloon hovercraft experiments. I need to find the relationship between the amount of air pumped into the balloon and how long the...
  36. Harperchisari

    Thermodynamics in an ion beam?

    Hi there, I'm trying to design an ion beam source, but having some issues with the thermodynamics of it. I'm no expert in thermodynamics, but I do understand some. I'm trying to find an equation which I can use to find the amount of energy I need to put into a set mass of a set material in order...
  37. Zeynaz

    How Do I Calculate Temperature in a Thermodynamics Problem?

    So, I converted the V (milk) to m3 and found 1.8E-4 m3 and i already know the density so i found the mass of the milk in the bottle. Mmilk= 1.9E-7 kg Normally i would try to connect it with the formulas above but i don't know temperature. I am not sure how i can connect the dots. Can...
  38. C

    Energy and first law thermodynamics help

    Hey guys, Have a thermodynamics exam coming in the next few days up based on the following topics. Energy and first law, Thermodynamic properties, First law: closed systems, First law: open systems/specific heat. When I have taken a look at the past exams it has been all calculations and...
  39. M

    Thermodynamics: Joule / Brayton Cycle - Specific Work Done Question

    Relevant Equations: Specific Work Done: w = \frac{p_2 v_2 - p_1 v_1}{1-\gamma} (1) w = \frac{R}{1-\gamma} \times (T_2 - T_1) (2) Thermal efficiency: \eta _{th} = 1- \frac{1}{r_p ^ {\frac{\gamma - 1}{\gamma}}} = \frac{w_{out} - w_{in}}{q_{in}} = \frac{q_{out} - q_{in}}{q_{in}} (3) Context...
  40. W

    Thermodynamics: Partial derivatives

    Hi all, I have had the following question in my head for quite a while: Thermodynamic potentials written in differential form look like $$dU = TdS - PdV$$ and we can obtain equations for say, temperature by doing the following partial $$T = \frac {\partial U}{\partial S} |_V$$ Does this mean...
  41. Zouatine

    Question in thermodynamics -- Two paths on a P-V diagram....

    Hi every one , I have this question today : The two arrows in the figure show two thermodynamic processes of a certain amount of ideal gas. The dashed line is a hyperbola. Which of the following statements is not true? a. The heat transfer is the same in the two processes. b. The temperature...
  42. TheBigDig

    Efficiency of the Rankine Cycle

    WT, the work done by the turbines, as the difference in enthalpy from point 2 to point 3 WP, the work done by the pumps as the difference in enthalpy from point 4 to point 5 Q as the difference in enthalpy from point 3 to point 4 Taking these I get h5 = -252.3kJ/kg. However, my work ratio is...
  43. QuasarBoy543298

    The zeroth law of thermodynamics

    let's assume I have 2 systems A and B. the surface that describes when the 2 systems are in equilibrium is given by F(a1,a1,...,b1,b2,...) = 0. assuming we can write this surface as A(a1,a2,..)=B(b1,b2,...) why do A and B describes the temperature function of the systems? in class, we...
  44. TheBigDig

    Efficiency of a steam power plant

    My inital assumption was to just take T1 = 5600 and T2= 300K, find the maximum efficiency and then divide it by two and three but I don't believe this question to be that simple. I'm confused as to where the 750K fits in as I thought no matter what occurred in between the heat reservoir and heat...
  45. M

    Chemistry Molar solubility lab questions

    I’m confused on how to calculate molar solubility because I don’t see what’s the difference between that and Ksp.
  46. FEAnalyst

    Thermodynamics - time to cook an egg

    Hi, as Easter is slowly approaching, I came up with an egg cooking thermodynamics problem that I would like to solve. My formulation of the problem including necessary simplifications is as follows: Let's assume that an egg is a sphere-shaped solid body made of homogenous material (ignoring...
  47. C

    Why is air in atmospheric pressure and room temperature a gas?

    This seems like a simple thermodynamics question but I would like clarification. So the absolute critical temperature is 132.5 K (-221.17 F) and the absolute critical pressure is 3.77Mpa (546.7 psi). I understand that for temperatures above the critical point, a pure substance undergoes an...
  48. babaliaris

    How Do You Calculate Heat Transfer in a Thermodynamics Piston Problem?

    I'm new to thermodynamics and after some reading I tried to solve the problem below but I have stuck (I think this problem assumes you know only the first law of thermodynamics) You have a piston resting on some stops inside a container filled with water and you want to find out after heating...
  49. M

    Thermodynamics: Insulated Box Partition Question

    Homework Statement A thermally insulated, rigid vessel is divided into two equal compartments. One contains steam at 100 bar and 400 degrees Celcius, and the other is evacuated. The partition is removed. Calculate the resulting pressure and temperature. (Please let me know if this is the wrong...
  50. M

    Thermodynamics of an Insulated Box: Water-Steam Question

    Homework Statement A sealed, thermally insulated tank of volume 2 m^3 has a safe working pressure of 4 bar. At 20 degrees Celcius, 10% of the volume is occupied by water, the remainder by water vapour. Calculate how much heat can be added without exceeding the safe working pressure. This...
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