(Hopefully) simple thermodynamics question

  • Context: Undergrad 
  • Thread starter Thread starter AxiomOfChoice
  • Start date Start date
  • Tags Tags
    Thermodynamics
Click For Summary
SUMMARY

The discussion centers on the thermodynamic behavior of an ideal gas in a thermally isolated piston during compression. When work is done on the gas, as indicated by the equation \(\Delta U = Q + W\), the internal energy (\(\Delta U\)) increases due to the work (\(W\)) applied, resulting in a rise in temperature (\(\Delta T > 0\)). This temperature increase occurs because the kinetic energy of the gas molecules rises as they gain momentum from the compression, analogous to the effect of hitting a tennis ball with a racket.

PREREQUISITES
  • Understanding of the first law of thermodynamics
  • Familiarity with the concept of internal energy in thermodynamics
  • Knowledge of ideal gas behavior and properties
  • Basic grasp of kinetic theory of gases
NEXT STEPS
  • Study the first law of thermodynamics in detail
  • Explore the kinetic theory of gases and its implications
  • Learn about the specific heat capacities of ideal gases
  • Investigate real gas behavior and deviations from ideality
USEFUL FOR

This discussion is beneficial for students and professionals in physics, engineering, and thermodynamics, particularly those interested in the principles governing gas behavior under compression.

AxiomOfChoice
Messages
531
Reaction score
1
Suppose you have a piston of ideal gas that's thermally isolated from its surroundings. You compress the gas by pushing down on the piston. Question: Does the temperature of the gas change, and why?

My answer: YES, it changes. Since [itex]\Delta U = Q + W[/itex], and work was done ON the gas (by compressing it), [itex]\Delta U > 0[/itex]. Since the energy of an ideal gas is only dependent on the temperature of the gas, this implies [itex]\Delta T > 0[/itex].
 
Science news on Phys.org
Yes, it is increasing because with the piston you increase the momentum of the molecules that are bouncing of it, increasing their speed and with that their kinetic energy, that is like hitting a tennis ball with a racket.
You see the equation in the right way.
 

Similar threads

Undergrad Joule-Thomson Expansion
  • · Replies 4 ·
Replies
4
Views
1K
Undergrad Irreversible adiabatic processes & entropy change (clarification needed)
  • · Replies 22 ·
Replies
22
Views
6K
Undergrad About Reversible vs Irreversible Gas Compression and Expansion Work
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Sign convention on work done to a closed system containing gas
  • · Replies 5 ·
Replies
5
Views
4K
Undergrad Focus Problem for Entropy Change in Irreversible Adiabatic Process
  • · Replies 60 ·
3
Replies
60
Views
11K
Undergrad Yet again about (real) gas compression
  • · Replies 20 ·
Replies
20
Views
4K
High School Energy seems to disappear when gas is compressed?
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Work in hydrostatic system in cylinder with piston: P_int or P_ext?
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Trying to wrap my head around gas turbine thermodynamics
  • · Replies 5 ·
Replies
5
Views
4K
Undergrad How can visible gas bubbles remain intact inside frozen water?
  • · Replies 8 ·
Replies
8
Views
2K