In all substances, the thermal energy of the particles is greatest in the gas state. This is because gas particles move freely and rapidly, with minimal intermolecular interactions constraining their motion, which gives them the highest average kinetic energy among the three common states of matter (solid, liquid, gas). Key points:
- Thermal energy includes the kinetic energy of particles (and, in some contexts, potential energy associated with particle spacing). For pure gases, the kinetic component dominates because particles are far apart and collide infrequently but with high speeds, leading to high overall energy per particle compared with solids and liquids. This is why a gas at a given temperature typically has higher average particle kinetic energy than a solid or liquid at the same temperature.
- In solids, particles vibrate about fixed positions with strong intermolecular forces, giving low kinetic energy and thus lower thermal energy overall.
- In liquids, particles are less tightly bound than in solids and can flow, yielding more kinetic energy than a solid but less than a gas.
If you’d like, I can tailor this explanation to a specific substance (e.g., water, carbon dioxide) and show how heating curves reflect the distribution of energy across states.
