Final answer:
The theory that explains gas behavior at the molecular level is the kinetic molecular theory of gases, which elaborates on how gas molecules move and interact, and helps in understanding various gas laws such as Boyle's, Charles's, and Avogadro's Laws.
Step-by-step explanation:
The theory that attempts to explain gas behavior at the molecular level is known as the kinetic molecular theory of gases. This theory provides a molecular-level explanation for the behavior and properties of gases, assuming that gases consist of widely separated molecules in constant motion, with collisions between them being perfectly elastic. It effectively explains ideal gas behavior and contributes to our understanding of the various gas laws, including Boyle's Law, Charles's Law, and Avogadro's Law, which are special cases of the ideal gas law. The kinetic molecular theory is based on assumptions that correlate closely with the known behavior of gases, offering insights into the relationships among pressure, temperature, volume, and the amount of gas.