# What is Themodynamics: Definition and 21 Discussions

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1. ### B Efficient way to warm a concave body such as Pita bread

What is the optimal and efficient way to warm a concave body on a plain source of heat (such as heating concave pita bread) on its peak top or opposite (on the larger surface with gap)? Imagine you have a body in U shape. Is the best way to warm it with the U position or opposite?
2. ### Irreversible isothermal Process Work External pressure not provided

It is clear that the process is isothermal else it is not possible to find heat absorbed. $$W=-P_{ext}(\Delta V)$$ However ##P_{ext}## is not given. How do I proceed? I tried taking ##W=-(P_2V_2-P_1V_1+P_3V_3-P_2V_2)=\Delta(PV)## but it is wrong for obvious reasons.
3. ### Thermodynamics - Hot copper block dropped in ice water

1) Q=m*L -.10*333 2)Q=mc deltat -.10*381*180-0 im unsure about the rest

7. ### Thermal expansion of air bubbles in plastic

I am interested in the potential for air bubbles in a plastic structure to expand with heat, and put pressure on the plastic surrounding the air bubble. In this case the plastic structure is formed by melting a thermoplastic powder. In between the grains of powder are voids with air in them. As...
9. ### I Minimization of thermodynamic equilibrium

Hi, I don't understand what does it mean that at equilibrium the proper thermodynamic potential of the system is minimized. For example on the book Herbert B. Callen - Thermodynamics and an Introduction to Thermostatistics it is written: Helmholtz Potential Minimum Principle. The equilibrium...
10. ### I Request for an example of minimum energy principle (thermodynamics)

Summary: Request for an example of minimum energy principle usage The minimum energy principle states that, for a system at constant entropy, volume and other extensive quantities, the internal energy is minimized at equilibrium. Can you give me an example in which, using this principle, is it...
11. ### Enthelpy and Isentropic compression/expansion

In a certain thermodynamics textbook, specific work done by an isentropic compressor/pump in an ideal rankine cycles, is given by the following; Wpump = h2 - h1 Wpump = v(P2 - P1), where v = v1 When I carry out these two calculations between any two states, I get vastly different answers...
12. ### Relating the entropy of an ideal gas with partial derivatives

It looks very easy at first glance. However, the variable S is a variable in the given expression. I have no clue to relate the partial derivatives to entropy and the number of particles.
13. ### Heat Question -- Temperature rise of a hiker on a long hike

Homework Statement A 80.4 kg hiker uses 212 kcal hr-1 (3 s.f.) of energy whilst hiking. Assuming that 20% of this energy goes into useful work and the other 80% is converted to heat within the body, calculate the temperature change, in units of Kelvin (K), of the hiker's body during a 1.6 hour...
14. ### What is the molar heat capacity of an ideal gas at constant pressure and volume?

Homework Statement 117 J of energy is supplied as heat to 2.00 moles of an ideal gas at constant pressure, the temperature rises by 2.00 K. Calculate the molar heat capacity at constant pressure C_p,m and the molar heat capacity at constant volume C_v,m for the gas. Is the gas monatomic or...
15. ### How does compression cool water in a household water cooler?

How does compression cool water in a household water cooler? I was reading and it says, " The water inside the water cooler is fed into a reservoir, where it is cooled using a refrigerant. A refrigerant is a cooling medium that is circulated in pipes that are located close to the reservoir in...
16. ### Themodynamics: calculating the partial pressure with Dalton's Law

Homework Statement In a sealed container is Helium ##M_{He} = \frac {4kg} {kmol} ## with a pressure of ## p_{He} = 4bar##. now is Methan put isothermic inside the container till both the methan and the helium mass are equal( ##M_{CH4} = \frac {16kg} {kmol} ## Calculate using the ideal gas law...
17. ### Classical Are There Good Thermodynamics and Optics Books for Physics Students?

Hi I'm a physics student in university, I want to find a book about general thermodynamics which has great and interesting problems. Includes a bit of statistical physics and molecular physics. And a book has theory and problems about optics, wave optics and geometrical optics. Thanks for helping
18. ### Ice sublimating to water vapor

Suppose an ice cube is in a vessel and it is at a temperature slightly below 0 degrees Cesius. Suppose further that the inside of the vessel is a vacuum. If the temperature of the vessel is increased to slightly above zero Celsius and the vacuum is maintained would the state change in the ice...
19. ### Callen Thermodynamics 2.8-2 matter flow equilibrium

Homework Statement A two component gaseous system has a fundamental equation of the form $$S=AU^{1/3} V^{1/3} N^{1/3} + \frac{BN_1N_2}{N}$$ where $$N=N_1+N_2$$ and A and B are positive constants. A closed cylinder of total volume 2V_0 is separated into two equal subvolumes by a rigid diathermal...
20. ### Solve Thermodynamics Problem: Expansion Irreversibly and Isothermally at 27°C

Expansion irreversibly and isothermally of an ideal has from a volume of 2dm3 to 10 dm3 against a const pressure of 1 atm at 27 C .Find entropy change of the system and also surroundings due to the process. Heres my attempt: delta S=energy absorbed/temp for the system, = energy...
21. ### Reactions and Themodynamics Related Question

1.) (a) Give the reaction, with molecular structures, of 2-propanol with KMnO4 and 1-pentanol with KMnO4 and calculate the differences in the average bond energies of the reactants and products (ignore KMnO4 and any other side reactions in the calculations). Answer:- the reaction, with...