Theories in chemistry provide frameworks for understanding the behavior of matter at the molecular level. They help explain phenomena like chemical reactions, bonding, and the properties of substances. One foundational theory is the atomic theory, proposing that matter is composed of indivisible particles called atoms. Another is the kinetic molecular theory, which describes the behavior of gases based on the motion of particles. Quantum mechanics, a more advanced theory, explores the behavior of atoms and molecules using mathematical models. Additionally, theories like thermodynamics and electrochemistry elucidate energy changes and electron transfer in chemical systems. These theories collectively underpin modern chemistry.