Kinetic energy of molecules in liquid state?
The average translational kinetic energy of a molecule is $3kT/2$ irrespective of whether the molecule is in the gas, liquid, or solid phase.  In the liquid the motion giving rise to kinetic energy is restricted to a narrower range about the potential energy minimum  than it is in the gas phase. The equipartition theorem is quite general. A derivation is given here;  Derivation of mean kinetic energy

For ideal gases, the result may also be derived via kinetic theory. However, the most general derivation comes from the equipartition theorem.