According to particle theory, which statement is true about energy, particle speed, and temperature?

• A. The higher the energy, the faster the particles move, the higher the temperature.
• B. The higher the energy, the slower the particles move.
• C. Particles do not move at all.
• D. Energy does not affect particle speed.

Answer: (A)

Energy added to a substance shows up as motion of its particles. Temperature measures the average kinetic energy, which is the energy of motion, of those particles. When energy is increased, the particles gain speed on average, their kinetic energy rises, and the temperature increases. That direct link—more energy, faster particles, higher temperature—fits what we observe in everyday heating.

Note that during a phase change (like melting or boiling), added energy can go into breaking bonds rather than raising motion, so temperature stays the same until the change finishes, then it rises again with more energy. The ideas that particles don’t move, move more slowly with more energy, or that energy doesn’t affect speed don’t align with how temperature and motion are related on the particle level.