Which of the following best describes the first law of thermodynamics?

energy always changes from a more useful, more concentrated form to a less useful, less concentrated form
in a closed system of constant mass, the energy involved in any physical or chemical change is neither created nor destroyed, ut merely changed from one form to another
heat always flows from a hot body to a cold body
the entropy of a system increases as the state of disorganization in the system increases
in a reversible process, the entropy of a system's constant, whereas in an irreversible process, the entropy of the system increases