The concept of effective mass is crucial in understanding various phenomena in physics, from the behavior of electrons in solids to the properties of quasiparticles in condensed matter systems. Atkins discusses the role of effective mass in understanding the behavior of particles in different contexts, including the behavior of electrons in atoms and molecules.
The second law of thermodynamics, formulated by Sadi Carnot, Rudolf Clausius, and William Thomson (Lord Kelvin), states that the total entropy of an isolated system always increases over time. Entropy, a measure of disorder or randomness, is a fundamental concept in thermodynamics that characterizes the direction of spontaneous processes. Atkins explains that the second law is a consequence of the asymmetry of time, which implies that the future is different from the past.
Clausius, R. (1850). On a mechanical theory of heat.