List the characteristics of internal energy.

Explanation

(i)Internal energy of a system is an extensive property. It depends on the amount of the substances present in the system.
(ii) Internal energy of a system is a state function. It depends only upon the state variables (T,P,v,n) of the system .
(iii)The change in internal energy is as `DeltaU=U_2-U_1`
(iv)In a cyclic process, there is no energy change. `DeltaU_"cyclic"=0`
(v) If the internal energy of the system at final state `(U_f)` is less than the internal energy of the system at its initial state `(U_i)`, then `DeltaU` would be negative.
(vi)If `U_f lt U_i " " DeltaU=U_f- U_i`=-ve
If `U_f > U_i " " DeltaU=U_f - U_i`=+ve