A theory that explains the behavior of gases on a molecular level.

• A. Ideal gas law
• B. Dalton's law
• C. Kinetic Molecular Theory
• D. Boyle's law

Answer: (C)

Gas behavior at the molecular level is explained by the Kinetic Molecular Theory, which says that gases are made of many tiny particles in constant, random motion. These particles are far apart compared to their size, so the volume they themselves occupy is negligible. They collide with each other and with the walls of their container in perfectly elastic collisions, meaning no energy is lost in the collisions. The pressure we measure comes from these frequent collisions with the container, and temperature reflects the average kinetic energy of the particles—the higher the temperature, the faster the particles move, and the greater the average kinetic energy. Because there are no significant intermolecular forces in this theory, changes in pressure, volume, and temperature can be understood by how particle speed and collision frequency respond to conditions. The other statements describe relationships between properties (like P, V, n, T) or specific gas-law behavior, but they don’t provide the mechanism by which gas molecules move and interact.