🔍 Key Concepts

• Internal energy as the sum of molecular kinetic and potential energies • How temperature relates to average kinetic energy of molecules • How state of matter (solid, liquid, gas) changes spacing/attraction between molecules (potential energy)

💭 Think About

• Ask yourself: which part of molecular energy (kinetic vs potential) is most directly tied to temperature changes? • Think about what happens to molecules when a solid melts or a liquid boils at constant temperature—what kind of energy is changing then? • For each choice, separate the statements about potential energy and kinetic energy and check if each one makes physical sense.

✅ Before You Answer

• Be sure you know that temperature is directly related to average kinetic molecular energy. • Confirm how changes of phase (solid ↔ liquid ↔ gas) affect molecular spacing and attraction, which is potential energy, even when temperature doesn’t change. • Eliminate any choice that says a type of molecular energy is “in no way related” to something you know it clearly depends on (temperature or state).