How does the source define the internal energy U of a system, using the atomic and molecular point of view?
AThe total heat transferred into the system over time
BThe total work the system has performed historically
CThe kinetic and potential energy of its atoms and molecules
DThe total pressure exerted by its atoms and molecules
Answer & Solution
Correct answer: C. The kinetic and potential energy of its atoms and molecules
1. The atomic and molecular view examines a system in terms of its individual atoms and molecules.
2. From that view, the source defines internal energy U as the sum of the kinetic and potential energies of all those atoms and molecules.
3. Heat and work are both energy in transit into or out of a system, not the stored energy itself, so options A and B describe the wrong quantities.
4. Pressure is a macroscopic quantity related to force per area, not a sum of atomic energies, so option D is not the definition given.
_Source: OpenStax College Physics (CC BY 4.0), Ch 15 "Thermodynamics", section 15.1 The First Law of Thermodynamics_
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