List the characteristics of internal energy.

Explanation

The internal energy of a system is an extensive property.
The internal energy of a system is a state function.
The change in internal energy of a system is expressed as `DeltaU=U_(f)-U_(i)`
In a cyclic process, there is no internal energy change `DeltaU_("cyclic")=0`
If the internal energy of the system in the final state `(U_(f))` is less than the internal energy of the system in its initial state `(U_(i))` , then `DeltaU` would be negative.
`DeltaU=U_(f)-U_(i)=-ve(U_(f)ltU_(i))`
If the internal energy of the system in the final state `(U_(f))` is greater than the internal energy of the system in its initial state `(U_(i))` , then `DeltaU` would be positive.
`DeltaU=U_(f)-U_(i)=+ve(U_(f)gtU_(i))`