Internal energy in the first law of thermodynamics

The definition of the internal energy of a thermodynamic system in most introductory texts usually states or implies that the c.m. kinetic energy of the system is not part of the internal energy. This is inconsistent with their statement of the first law of thermodynamics as ΔU=Q−W. If the c.m. kinetic energy is not considered part of U, the first law should be stated as ΔU+ΔKc.m.=Q−W. Several examples are given. Clarification of this point is needed in many widely used texts.