What is the relationship between atoms and molecules?

Molecules are indeed made up of atoms, which is the correct relationship described in this context. Atoms are the fundamental building blocks of matter and represent the simplest unit of an element, consisting of protons, neutrons, and electrons. When two or more atoms bond together chemically, they form a molecule. This can include molecules that consist of the same type of atom, like O2 (oxygen gas), which contains two oxygen atoms, or different types, such as H2O (water), which consists of two hydrogen atoms and one oxygen atom.

Understanding this relationship is crucial in many fields, including HVAC, as it lays the foundation for comprehending how substances behave during changes in state, reactions, and the effects of temperature and pressure changes within the refrigeration cycle. It emphasizes the importance of atomic and molecular interactions when designing efficient systems for cooling and heating.