Change in Internal Energy
Moderators: Chem_Mod, Chem_Admin
-
- Posts: 50
- Joined: Sat Jul 22, 2017 3:00 am
- Been upvoted: 1 time
Change in Internal Energy
When you compress a system, is that considered the system doing work or work being done on the system? How does that affect internal energy and how can I remember?
-
- Posts: 31
- Joined: Fri Sep 29, 2017 7:05 am
Re: Change in Internal Energy
Compression is work being done on the system. Remember the equation is delta U = q + w. Internal energy, U, will increase because work (w) is a positive value.
-
- Posts: 51
- Joined: Fri Sep 29, 2017 7:04 am
Re: Change in Internal Energy
Hi!
Compression of a gas means that work is being done on the system. When we look at deltaU= q + w, we are looking at it from the perspective of the system. So because the system is not losing any energy by doing work (its surroundings are instead), the sign of work will be positive. So, compression increases the internal energy of a system.
-w=when the system is doing work
+w=when the surroundings are doing work on the system
Hope this helps :)
Compression of a gas means that work is being done on the system. When we look at deltaU= q + w, we are looking at it from the perspective of the system. So because the system is not losing any energy by doing work (its surroundings are instead), the sign of work will be positive. So, compression increases the internal energy of a system.
-w=when the system is doing work
+w=when the surroundings are doing work on the system
Hope this helps :)
-
- Posts: 48
- Joined: Fri Sep 29, 2017 7:04 am
- Been upvoted: 1 time
Re: Change in Internal Energy
If it helps to remember, it's basically the first law of thermodynamics! If you think about the "compressing a piston" example, the person is clearly doing work by pushing on the piston, or exerting a force over a certain distance. And force x distance = work, which is a form of energy.
Return to “Phase Changes & Related Calculations”
Who is online
Users browsing this forum: No registered users and 11 guests