What is Thermodymanics: Definition and 16 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. E

    I Helmholtz entropy of ideal gas mixture is additive?

    In his classic textbook, Callen remarks that I have labelled the claims (1) and (2). I am not sure about either. For the first, I have tried to proceed as follows (all equations are from Callen's second edition and all 0 subscripts are with respect to some reference state of an ideal gas): I...
  2. E

    I How can the maximum entropy and minimum energy principles be physical?

    In Chapter 5 of his famous textbook on thermodynamics, Callen argues for the "equivalence" of the maximum entropy (Max-Ent) principle and the minimum energy (Min-En) principles. I quote from Callen first: As far as I know (though Callen never makes this explicit in what, I think, represents...
  3. E

    I How to know when a reversible process between end states exists?

    I am continuing to try to understand maximum work reversible processes (and a subset thereof -- Carnot cycles) better. I am here curious about the following system. My question is about how I can know/prove that there exists a way to take the gas (the primary subsystem) reversibly with respect...
  4. E

    I Confusion on Callen's Maximum Work Theorem

    This question was, effectively, asked here (please refer to that question for additional context); however, I don't think the given answer is correct (or at least complete) despite my having added a bounty and having had a productive discussion with the answerer there. In particular, I don't...
  5. V

    I Cannot understand formula for molar heat capacities of an ideal gas

    Homework Statement:: I am trying to understand a formula given in our book for determining molar heat capacity of an ideal gas under different thermodynamic processes using a single formula, but it is confusing. The exact formula for different processes is in the screenshots below. Can someone...
  6. D

    Specific heat in for the Otto cycle

    A class project requires us to model the Otto cycle using ideal gas properties. We are not given the value for qin (specific heat in) and are told to make an intelligent approximation. My approach to this has been to find the calorific value of petrol, multiplying this by the density of petrol...
  7. questionmonkey123

    Constant pressure process (piston) on gas violates Newtons 2nd law?

    I often see this set up in thermodynamic problems and need clarification on how Newton's Laws are involved for the piston: Gas inside a piston cylinder (1) is heated expanding the gas and raising the piston (initially at rest) to a height (2) in a constant pressure quasi-equilibrium process...
  8. R

    Mathematics necessary for Radiometry, Photometry, Thermodynamics

    What are the math concepts I have to learn for Radiometry, Photometry and Thermodynamics (all Calculus-based) as applied in building science (engineering, architecture, etc.). I'm almost done with Multivariable Calculus and I'm aware that MV Calculus is necessary, but what specific calculus...
  9. freek_g

    Proving Gibbs energy equals work

    Hi, I'm preparing for my exams in a few weeks, of which one covers Thermodynamics. I was trying to solve a question, where I noticed the Gibb's free energy had to equal the (negative) work. I kind of came to an answer, but was not sure if I did it the right way. All steps are reversible...
  10. G

    How many basic states are there?

    Homework Statement Four distinguishable particles move freely in a room divided into octants (there are no actual partitions). Let the basic states be given by specifying the octant in which each particle is located. 1. How many basic states are there? 2. The door to this room is opened...
  11. S

    Problem with boiling water and raising piston

    Homework Statement Consider a cylindrical tank closed by a movable piston with mass ##m=3 kg##. The radius of the cyclinder is ##r=7.5 cm##. In the tank there is a mass ##m'=2 kg## o water at temperature just below ##100°C##. At the base of the cyclindrical tank there is an electrical heater...
  12. Nemo's

    Calculate Turbine gross and net output

    Homework Statement A steam power plant consists of a boiler, a turbine, a condenser and a pump. The temperature of the inner walls of the boiler is 350oC and the temperature of the condenser cooling water is 20oC. During a certain interval of time, the heat added to the boiler is 2.9x106 kJ and...
  13. A

    Is pressure a qualitative property?

    I was solving some examples and one of the examples states that pressure is a qualitative property, i searched a lot on the internet but i didn't find any explanation , i didn't even find any proof that this is true.
  14. F

    What happens to entropy when doubling the volume?

    Homework Statement A container of volume 2V is divided into two compartments of equal volume by an impenetrable wall. One of the compartments is filled with an ideal gas with N particles. The gas is in equilibrium and has a temperature T. How does the total energy, the entropy, the temperature...
  15. N

    Thermodymanics dealing with pressure, temperauture, and constants

    Homework Statement A bubble of air, 0.010m^3 in volume , is formed at the bottom of a lake which is 30m deep and where the temoperature is 8 degrees c. The bubble risees to the surface, where the water temp is 26 deg c and where the pressure is atmospheric pressure. What is the volume of the...
  16. N

    Thermodymanics heat loss question. Please help

    Question: How much heat is lost in one hour through a 15 cm x 3.7m x 6.1m concrete floor if the inside temperature is 22 degrees c and the ground temperature is 13 degrees c? some info: thermal conductivity of concrete=1.1 change in temperature=8 Relative Equations: kAchangeT/L...