for a given substance, in which state of matter is the thermal energy of the particles the greatest? explain.

For a given substance, the particles have the greatest thermal energy in the gas state.

Key idea

• Thermal energy is the total kinetic energy of all the particles in a substance; faster, more spread‑out particles mean higher thermal energy.

• In gases, particles move much faster and are much farther apart than in liquids or solids, so their kinetic energy (and therefore thermal energy) is highest.

• For the same substance at comparable conditions, this makes the gas state have more thermal energy than the liquid state, and the liquid more than the solid state.

So, for a given substance:
solid → least thermal energy, liquid → more, gas → greatest thermal energy.