What does the theory of molecular motion state?

Prepare for the HVAC 403A Exam. Study with flashcards and multiple choice questions, each question has hints and explanations. Get ready for your exam!

The main idea being tested is that matter is made of tiny particles in constant motion and that how vigorously these particles move is tied to temperature and how matter behaves. This concept underpins many HVAC phenomena, such as why heating makes materials expand and how molecular activity relates to properties like density indirectly through changes in volume. The statement that all matter is composed of constantly moving molecules captures this fundamental behavior. It also links the amount of movement to the material’s density in a way that aligns with how increased motion tends to spread particles out (expansion) and decreased motion allows them to come closer (contraction). The other claims don’t fit: density isn’t determined only by chemical makeup, since density also changes with volume effected by temperature; molecules in solids are not truly stationary—they vibrate; and temperature isn’t independent of molecular motion—it reflects the average kinetic energy of the molecules.