Summary
This section bridges microscopic and macroscopic properties of matter by introducing the atomic mass unit and defining the mole with Avogadro’s number. It then connects these concepts to the ideal gas law and kinetic theory, which reveal the relationship between gas pressure, volume, temperature, and molecular motion. Finally, diffusion and Fick’s law are explored, illustrating how molecules move from high to low concentrations, a process vital in both natural phenomena and engineered systems.