Internal energy Definition and 381 Threads

Hello PF! I have some questions regarding these concepts. First of all, are the following expressions valid for any case? i.e. any kind of process, like isochoric, isobaric. \Delta U = \int C_v \ dT \Delta H = \int C_p \ dT Or is the ΔU expression only valid when dV = 0, and ΔH when dP = 0...

Hi,If the change in U between 2 points (A,B) in a thermodynamic process is always the same despite the path, then please help with the following: Say I have adiabatic conditions so that delta U = Work done only (Q=0) Surely I can go through multiple paths between A+B with increased or decreased...

Hi Guys! I have a confusion which I hope you can help clear up. The mathematical expression of the first law of thermodynamics can be stated as δu=Q+W where u is the internal energy of the system, Q is the heat added(or taken from) to the system and W is the work done by or on the system. If I...

Definition/Summary In thermodynamics, internal energy, U, is the energy associated with the microscopic energies of a system, that is with the energy associated with the random motion of the molecules within a system. More generally, while external energy is energy due to macroscopic...

Given that U = (3/2)PV does this mean that ΔU = Δ(3/2)PV for an ideal gas? Hence when finding the change in internal energy using a P-V diagram, can we simply apply this equation instead of using ΔU = Q+W?

Why the kinetic energy is same as internal energy of ideal gas?

Hi everyone. I thought of a question which has been bothering me. It is: Is there a case where energy is added to an ideal gas of constant amount where the energy added will equal the work done by the gas. My thoughts: The energy of an ideal gas is proportional to the temperature. If the...

Thermodynamics -- change in internal energy of the system for the path Homework Statement A system comprising of an ideal gas is taken from State a to State b, as shown in Figure 9 below, along th epath acb. 200J of heat flows into the system and 80J of work is done by the system along the...

"What is the internal energy of 10 moles of helium at 100 K?" The same question is asked about 10 moles of oxygen. I'm going to guess PV=nRT which would give 8,314 J as the PV value. Because (at least in chemistry this is true) delta H = delat E +/- work and work = PV, so PV would somehow...

Homework Statement Two speeding lead bullets, one of mass 15.0 g moving to the right at 270 m/s and one of mass 7.65 g moving to the left at 390 m/s, collide head-on, and all the material sticks together. Both bullets are originally at temperature 30.0°C. Assume the change in kinetic energy of...

could anyone explain me the fundamental different between internal energy and enthalpy? I searched and found the below definitions for both terms. INTERNAL ENERGY:In thermodynamics, the internal energy is the energy contained by a thermodynamic system. ENTHALPY:Enthalpy is a measure of the...

Hello, ##E_{tot}^2=(pc)^2+(m_0 c^2)^2## works fine for mass ##m_0## moving with relativistic speeds. What if the moving mass has internal energy also (say, heat). Does the energy-momentum relation still apply? What is the expression for the momentum ##p## then? Because ##p=\gamma m_0 v##...

Then I see this line in a Wiki article: For an ideal gas, the heat capacity is constant with temperature. Accordingly we can express the enthalpy as H = n C_P T and the internal energy as U = n C_V T, where n is the amount of substance in moles. Thus, it can also be said that the heat...

Homework Statement The internal energy of a gas is 597 joules. The gas is compressed adiabatically and its volume decreases by 129 cm3. If the pressure applied on the gas during compression is 3.43 atm, what is the internal energy of the gas after adiabatic compression? Homework Equations...

Homework Statement The internal energy of a system is expressed by function U(S.V)=S4/3Vα, where α is a constant. The value of α is? The Attempt at a Solution Here internal energy is expressed in terms of volume and entropy but all the relations (as far as I know) are in terms of...

Wikipedia says its the TOTAL energy contained by a thermodynamic system. But the textbook says Total energy = internal energy + kinetic energy + potential energy

Homework Statement Heat flows into an ideal gas at a constant volume. The pressure increases from 1.5 atm to 5.5 atm. Next the gas is compressed at constant pressure from 5.0 L to 2.5 L and goes back to its original temperature. 1.What is the total work done on the gas in the process...

Homework Statement 400. g of oxygen has a volume of .25 m3 and a pressure of 125,000 Pa. What is the internal energy of the gas? What would the internal energy of the gas be if it were compressed to .10 m3 while the pressure was held constant?Homework Equations U = 3/2 PVThe Attempt at a...

I've got a few issues with the topic of thermodynamic expansion, ΔU, etc. With ΔU=q+w, this w is to mean work done on the system (positive contribution to ΔU) minus work done by the system (i.e. negative contribution to internal energy), so then how do we summarize this for cases of...

Homework Statement In exercising, a weight lifter loses 0.150 kg of water through evaporation, the heat required to evaporate the water coming from the weight lifter's body. The work done in lifting weights is 1.40x105 J. (a) Assuming that the latent heat of vapourisation of perspiration is...

Hi all, I was taught that internal energy of an ideal gas in depending on the temperature which mean during isothermal process, the change in internal energy is equal to zero. Is this statement true? How about the change in the internal energy of a substance when it is condensed from...

internal energy U=q+W so far we've only been substituting -PV into W but i just wanted to be sure that the W is the total work and not just the work done by the pressure right?

Hello everybody. The concept of internal energy of a real vs ideal gas has perplexed me. From what I understand, an ideal gas solely considers the kinetic energy of gas molecules (temperature) where as real gases consider kinetic energy of particles in addition to potential energy. So...

Homework Statement Two closed containers A and B contain equal number of moles of ideal gases GD (diatomic)and GM (Monoatomic) ,respectively. Q .1 a) If the temperature of gases are same,which of them has more average translational kinetic energy ? b) Which of them has more...

Change in internal energy at constant pressure?? Hello everybody, I am stuck with a concept in thermodynamics. We know that ΔU=CvΔT. But what if we want the change in internal energy at constant pressure? ΔU→Change in internal Cv=heat capacity at constant volume

In an isobaric process of 1 mole of a monatomic ideal gas, the pressure stays the same while the volume and temperature change. Let's take an isobaric expansion where the volume increases by 2m3 and the pressure stays at 5kPa. If the work done by the gas is the pressure times the change in...

17x10^5 joules are absorbed by an expanding gas that does 8x10^5 joules of work. (a) Find ΔU; (b) Assuming it expands at constant pressure, what's the change in volume? Am I correct to use this: ΔU = Q - W Then after finding ΔU, PΔV = Q - ΔU Or does this make no sense?

For incompressible substances you have a change in internal energy represented by ΔU = mcΔT where T is temperature. I've also seen ΔH = mcΔT and ΔQ = mcΔT where H and Q are enthalpy and heat, respectfully. Does that mean that all of these are the same? I heard H becomes U...

Hello all, So the total internal energy of a gas as far as I've been told is 3/2(NKT) but it can also be written as 3/2(PV). Why then is the internal energy only a function of temperature and not volume and pressure as well? Thanks in advance for the help.

This is the example 2.12 from "Introduction to Chemical Engineering Thermodynamics", 6th. ed, by Smith, Van Ness & Abbott: "An evacuated tank is filled with gas from a constant-pressure line. What is the relation between the enthalpy of the gas in the entrance line and the internal energy of...

Hello, this is my first post, so I apologize in advance if it's not quite up to par. Homework Statement A gas is compressed at a constant pressure of 0.639 atm from 5.41 L to 2.3 L. In the process, 470 J of energy leaves the gas by heat. a) What is the work done on the gas (J)? b) What...

I had a question : Heat energy was supplied to melt ice at -15 degree Celsius. But it was not enough to turn the ice completely into water at 0 degrees. From my calculation I obtained that a mixture of 60% water and 40% ice was produced as a result of heating. Finally it said to describe...

I am doing a simple thermodynamic analysis. Couldn't get thermodynamic values (such as internal energy, exergy, and so on) from common data base of CO2. I looked it up in REFPROP(By NIST) and EES. None of them have data below 212K. At one atmosphere CO2 sublime at about 195K. Could anyone...

Ok, if it says that change of internal energy is part(for example 1/3) of TOTAL work executed over system(body). Does it mean that is TOTAL work indeed sums of every single work(mechanical work+internal energy change+...) ?

The heat transfer equation is Rate = k•A•(T1 - T2)/d where k is the heat transfer coefficient of the material. But I'm feeling that the other material transferring the heat should be important too. I mean if I were to touch Styrofoam at 50 degrees and metal at 50 degrees, the metal feels...

Homework Statement Q.1)A gas cylinder is lifted from the ground floor to the first floor.What is the amount of work done on the gas?What is the amount of work done by the gas?Is the internal energy of the gas increased? Q.2)When we place a gas cylinder on a car and the car moves,does the...

Homework Statement A force F is applied on a block of mass M.The block is displaced through a distance "d" in the direction of the force.What is the work done by the force on the block?Does the internal energy change because of this work? Homework Equations The Attempt at a...

Given the following equation of state and C_p = 3R, find the equation of the internal energy in terms of T and V p(V-b) = RT Any clues? I can use also the specific heat at constant pressure or volume. Thanks!

Homework Statement Consider a pump that is required to compress air in a factory. The cylinder in the pump has an inner diameter of 2.00 cm and length 60.0 cm. Air is drawn into the pump at atmospheric pressure and 18°C and the pump adiabatically compresses the air to a pressure of 17...

Homework Statement Argon is a monatomic gas for which all the internal energy of the molecules may be considered to be translational kinetic energy. Molar mass of argon = 4.0 x 10-2 kg. The Boltzmann constant = 1.38 x 10-23 J kg-1 . The Avogadro constant = 6.02 x 1023 mol-1 ...

what is the change In internal energy of an ideal gas when it is expanded Adiabatically from (p °,v°) to ( p,v )? The relevant equations : dQ= dU+ pdv ; pV^ r = K (constant). r = Cp / Cv. Attempted solution : During adiabatic process dQ=0 ; p= k v ^ -r Th f r : du= -k v^ -rdv Integrating...

Hi, I regard an equation for an canonical ensemble. I do not understand why both equations should be equal. \bar{E}= -\frac{ \partial \ln{(Z)}}{ \partial \beta} \overset{\text{?}} = k T ^{2 } \frac{\partial \ln{(Z)}}{\partial T} Z is a canonical partition function. \beta = \frac{1}{kT}...

Hi, i regard a Brownian Particle connectet to a Spring and there is a heat-reservoir. The distribution of the x-coordinate of the particle follows the Diffusion-Equation (Fokker-Planck-Equation): \partial_{t}P(x,t)=\frac{D}{2} \partial_{x}^{2}P(x,t)- \Gamma\partial_{x}[f(x)P(x,t)] A...

How to relate the radiation pressure to the internal energy of an object?? How to get that formula P=u/3?? http://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law#Thermodynamic_derivation Thank you.

Homework Statement Expression for the entropy and internal energy of black body radiation. Using the below relations: Homework Equations Total free energy for black body: $$ F = (k_b TV/\pi^2) \int k^2 ln[1-exp(-\hbar ck/k_b T)]dk $$ Relationship between partition function and internal...

Homework Statement For those who are not interested in reading through the different values I get for each stage then please answer this question: What is the internal energy at state 1? When water is a saturated steam... Is it U_vap + U_liq since saturated steam has both liquid and...

What are the formulas for entropy and internal energy in Fermi-Dirac statistics, and how do I derive them?

1.While studying the thermodynamic properties of perfect gases I saw that the change in internal energy for constant volume process is mCvdT. but it is also the same for const pressure, const temp, const entropy and other reversible non-flow processes. Why is it so?? why it is not mCpdT for...

Six grams of water changes from liquid to vapor at a pressure of one atmosphere. In the process, the volume changes from 0.9 cm^3 to2387 cm^3. The latent heat of vaporization of water is 2.26 × 10^6 J/kg Find the increase in internal energy of the water. Answer in units of J When i...

A general thermo question... for the function describing internal energy U(S,V,A,N) U=TS-PV+γA+μN please explain how the total differential is dU=TdS-PdV+γdA+μdN (for a one component system) Basically why is dT=dP=dγ=dμ=0? Is it because they are intensive or potentials...