## Internal Energy of Isolated Systems

$\Delta U=q+w$

Anne 2L
Posts: 35
Joined: Fri Sep 29, 2017 7:05 am

### Internal Energy of Isolated Systems

The energy of an isolated system must remain constant because no matter or heat can be transferred and the system cannot be physically changed ($\Delta$V=0).
q=0 and w=0 then $\Delta$U=q+w=0

I just wanted to confirm that the internal energy of all isolated systems is 0? So for example, the internal energy of a system in a bomb calorimeter would always be 0?

Tim Nguyen 2J
Posts: 31
Joined: Sat Jul 22, 2017 3:00 am

### Re: Internal Energy of Isolated Systems

Yes, because I think that this is the first law of thermodynamics where energy is neither created nor destroyed :)

Anne 2L
Posts: 35
Joined: Fri Sep 29, 2017 7:05 am

### Re: Internal Energy of Isolated Systems

Can you elaborate on that?

Tim Nguyen 2J
Posts: 31
Joined: Sat Jul 22, 2017 3:00 am

### Re: Internal Energy of Isolated Systems

Yeah of course! As Dr. Lavelle discussed in class, the internal energy of an isolated system is constant. Since the universe is defined as an isolated system, the summation of all the work and heat transferred in the universe is constant. Therefore the change in internal energy (delta U) of the universe is zero.

Anne 2L
Posts: 35
Joined: Fri Sep 29, 2017 7:05 am

### Re: Internal Energy of Isolated Systems

Thank you so much for all the help!

I was just wondering how having constant internal energy equates to energy being neither created nor destroyed.

DamianW
Posts: 35
Joined: Fri Sep 29, 2017 7:06 am

### Re: Internal Energy of Isolated Systems

constant volume means no work

Nicholas Le 4H
Posts: 74
Joined: Fri Sep 28, 2018 12:24 am

### Re: Internal Energy of Isolated Systems

Yes, the change in internal energy of an isolated system is 0.