Internal energy change in isobaric system

In summary: There is no direct relationship between Cp and dU. Cp is a function of temperature while dU is a function of pressure.
  • #1
cooper607
49
0
hi all, i have a confusion about the internal energy change and work done in a isobaric system...
suppose i want to find the delQ in isobaric system in terms of P & V...now i may assume the delW part would be pdv=p(V2-V1)...as i m compressing the gas...
but what happens to the du?
and is the specific heat capacity at const pressure somehow related to the du?
please help
 
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  • #2
cooper607 said:
hi all, i have a confusion about the internal energy change and work done in a isobaric system...
suppose i want to find the delQ in isobaric system in terms of P & V...now i may assume the delW part would be pdv=p(V2-V1)...as i m compressing the gas...
but what happens to the du?
and is the specific heat capacity at const pressure somehow related to the du?
please help
Use the first law:

ΔQ = ΔU + W where W is the work done by the system.

If the compression is slow enough, you could treat it as a quasi-static isobaric compression such that W = PΔV.

To find ΔQ all you have to do is find ΔU. If this is an ideal gas, that is easy to do because ΔU is related to ΔT (how?) and ΔT is related to Δ(PV) by the ideal gas law. Or you could just use Cp and the change in T to determine ΔQ.

AM
 
  • #3
well as for ideal gas U is only function of T, so i think we can replace dU with dT...but i just don't want to split the delQ here...
so i wanted to know is there any direct link between Cp and dU so that somehow i can replace the dU in terms of Cp & dT?
 
  • #4
cooper607 said:
well as for ideal gas U is only function of T, so i think we can replace dU with dT...but i just don't want to split the delQ here...
so i wanted to know is there any direct link between Cp and dU so that somehow i can replace the dU in terms of Cp & dT?
What is the relationship between ΔU and ΔT (for an ideal gas? What is the relationship between Cv and Cp?

AM
 
  • #5


In an isobaric system, the pressure remains constant while the volume may change. The internal energy of a system is the sum of its kinetic and potential energies of all the particles within the system. The change in internal energy, denoted as ΔU, is equal to the heat added to the system, denoted as ΔQ, minus the work done by the system, denoted as ΔW.

In an isobaric system, the work done can be calculated as ΔW = PΔV, where P is the constant pressure and ΔV is the change in volume. This is because the work done in an isobaric process is equal to the product of the constant pressure and the change in volume.

As for the change in internal energy, ΔU, it is related to the heat added, ΔQ, and the work done, ΔW, through the first law of thermodynamics: ΔU = ΔQ - ΔW. Therefore, in an isobaric system, the change in internal energy can be calculated as ΔU = ΔQ - PΔV.

The specific heat capacity at constant pressure, denoted as Cp, is defined as the amount of heat required to raise the temperature of a unit mass of a substance by one degree at constant pressure. In an isobaric system, the change in internal energy is related to the heat added, ΔQ, and the specific heat capacity at constant pressure, Cp, through the equation ΔU = mCpΔT, where m is the mass of the substance and ΔT is the change in temperature.

In summary, in an isobaric system, the change in internal energy is related to the heat added and the work done, and the specific heat capacity at constant pressure is related to the change in internal energy. I hope this helps to clarify your confusion.
 

1. What is internal energy change in an isobaric system?

The internal energy change in an isobaric system refers to the change in the total energy of a system that occurs at constant pressure. It is a result of the system either gaining or losing heat, work, or both.

2. How is internal energy change calculated in an isobaric system?

The internal energy change in an isobaric system can be calculated using the equation ΔU = Q - PΔV, where ΔU represents the change in internal energy, Q represents the heat added or released by the system, P represents the constant pressure, and ΔV represents the change in volume.

3. What factors affect the internal energy change in an isobaric system?

The internal energy change in an isobaric system is affected by the amount of heat added or released by the system, the constant pressure, and the change in volume. The nature of the substance and any phase changes that occur can also impact the internal energy change.

4. How does the internal energy change in an isobaric system relate to the first law of thermodynamics?

The internal energy change in an isobaric system is a direct result of the first law of thermodynamics, also known as the law of conservation of energy. This law states that energy cannot be created or destroyed, but it can be transferred between different forms. In the case of an isobaric system, the change in internal energy is a result of the transfer of heat and work.

5. Can the internal energy change in an isobaric system be negative?

Yes, the internal energy change in an isobaric system can be negative. This occurs when the system releases more heat than it absorbs, resulting in a decrease in internal energy. It is also possible for the internal energy change to be positive, when the system absorbs more heat than it releases.

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