Question

Internal energy of a system is

• A. The average kinetic energy of all molecules
• B. The sum of potential energies of the atoms
• C. The sum of kinetic energies of all molecules in the system
• D. The sum of kinetic and potential energies of all molecules in the system.

Answer 1

Answer: (D)

The sum of kinetic and potential energies of all molecules in the system.

Answer 2

The internal energy of a system (U) is a state function that represents the total energy contained within the system. This energy includes:

1. Kinetic energy of the molecules: This includes translational, rotational, and vibrational kinetic energies of the molecules.

2. Potential energy of the molecules: This includes the potential energy due to intermolecular forces (forces between molecules) and intramolecular forces (chemical bonds within molecules).

It does not include the kinetic energy of the system as a whole (e.g., if the system is moving) or the potential energy of the system as a whole due to external fields (e.g., gravitational potential energy of the entire system).