Internal Energy of Isolated Systems

[Anne 2L]

I read this in the course reader:

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

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

[Anne 2L]

Can you elaborate on that?

[Tim Nguyen 2J]

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]

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]

constant volume means no work

[Nicholas Le 4H]

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