Thermodynamics - heat, internal energy, work

In summary, thermodynamics is the branch of physics that studies heat, internal energy, and work and their relationship to energy and work. Heat is the transfer of energy due to a temperature difference, internal energy is the total energy within a system, work is the transfer of energy due to a force acting over a distance, and the laws of thermodynamics govern the behavior of energy in a thermodynamic system. These laws state that energy cannot be created or destroyed, the total entropy of a closed system will increase or remain constant, and absolute zero temperature cannot be reached through any finite number of processes.
  • #1
Ampere
44
0

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?
2.What is the total change in internal energy?
3.What is the total heat flow of the process?

Homework Equations



U = Q + W
W = -P*ΔV

The Attempt at a Solution



1. No work is done in the first process because the volume is constant. The work done on the gas in the second process is W = -(5.5 atm) * (2.5 L - 5.5 L) = 1390J

2. The change in internal energy is 0 because there is no net change in temperature.

3. 1390J of heat must have left the system because U = Q + W.

Is this right?
 
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  • #2
Hello, Ampere.

Your process looks right, but I don't agree with your conversion from L-atm to Joules.

[EDIT: It's not the conversion, it's a typo in your equation W = -(5.5 atm) * (2.5 L - 5.5 L) = 1390J
where you wrote 5.5 L instead of 5.0 L.

I agree with your answer now.]
 
  • #3
Yes, I meant (2.5 L - 5.0 L). Thanks for the confirmation!
 

1. What is thermodynamics?

Thermodynamics is the branch of physics that deals with the study of heat, internal energy, and work and their relation to energy and work.

2. What is heat?

Heat is a form of energy that is transferred from one object to another due to a temperature difference between them. It can be measured in units of joules or calories.

3. What is internal energy?

Internal energy is the total energy contained within a system, including the kinetic and potential energies of its particles. It is a state function and is dependent on the temperature, pressure, and composition of the system.

4. What is work in thermodynamics?

Work is the transfer of energy from one system to another due to a force acting over a distance. In thermodynamics, work is defined as the force multiplied by the distance over which it acts.

5. What are the laws of thermodynamics?

The laws of thermodynamics are fundamental principles that govern the behavior of energy in a thermodynamic system. The first law states that energy cannot be created or destroyed, only transferred or converted. The second law states that the total entropy of a closed system will always increase or remain constant. The third law states that it is impossible to reach absolute zero temperature through any finite number of processes.

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