Laws of thermodynamics

[Jessica Castellanos]

What are the three laws of thermodynamics? I was a bit confused when they were mentioned in class.

[Eugene Chung 3F]

1. delta U = heat+work
2. For reversible system, deltaS of universe equals 0.
3. at 0K for a perfectly ordered molecule, the entropy change is 0

[Eesha Sohail 1D]

The corollary to law #2 is that since no real process is perfectly reversible, change in entropy of the universe is always positive, correct? But why can no real process be completely reversible?

[Esmeralda_Solis_2D]

1. States that the total energy of the universe is constant.
2. States that in all spontaneous processes the entropy increases.
3. States that for a pure crystalline substance at 0 K the entropy is zero.

[Reece Fong 2k]

1) Energy cannot be created or destroyed
2) Universe works to increase entropy
3) A pure crystalline substance at 0 kevlin has an entropy of zero.