States of Aggregation, Thermodynamic Phases, Phase Transformations, and the Vitreous State

Abstract

From a molecular-kinetic point of view all substances can exist in three different states, as gases, liquids and solids. These three states of aggregation of matter (from the Latin word: aggrego — to unite, to aggregate) are distinguished qualitatively with respect to the degree of interaction of the smallest units of the corresponding substances (atoms, molecules) and, consequently, with respect to the structure and mobility of the system.