Chapter 1: Atoms in Motion

Atoms in Motion establishes the atomic hypothesis—the central principle that all observable phenomena result from minute particles (atoms and molecules) engaged in perpetual motion, attracting one another over small distances yet repelling when forced too close. The introduction emphasizes that physics must be taught iteratively, as current knowledge is inherently approximate, serving as a stepping stone toward understanding the more complex, correct laws, such as those governing mass increase at relativistic speeds. The scientific method is defined by the critical role of experiment as the ultimate judge of truth, complemented by the necessary imagination required to hypothesize great generalizations from experimental hints. Applying the atomic theory explains the states of matter: in solids (like ice), atoms vibrate in fixed positions within a rigid crystalline array; in liquids (like water), molecular attraction maintains volume, but increased thermal motion (heat) allows molecules to flow past each other; and in gases (like steam), molecules separate entirely, exerting pressure on container walls through frequent, high-speed collisions, demonstrating that pressure is proportional to both density and temperature. Phase transitions are dynamic processes, such as evaporation, where high-energy molecules escape the surface, causing the remaining liquid to cool. Similarly, dissolving solids like salt involves water molecules electrically attracting and pulling apart ions from the crystalline structure, maintaining a dynamic equilibrium between leaving and returning particles. Finally, the chapter distinguishes these physical processes from chemical reactions, which involve the fundamental rearrangement of atomic partners to form new molecules, often releasing substantial kinetic energy, as seen in combustion (e.g., carbon forming CO or CO₂). Direct evidence supporting the atomic fact includes the observable, continuous jiggling of microscopic particles, known as Brownian motion, caused by atomic bombardment, reinforcing the central concept that all biological functions are rooted in atoms obeying the laws of physics.