This book not only describes the chemical and physical properties of water but also addresses the significance of water in everyday life and the associated political and social challenges. All biological systems require water to survive. Agriculture and industry depend on large quantities of freshwater, for example, for cooling, as a solvent, as a transport medium for substances and energy (especially thermal energy), or for chemical reactions. The scarcity of freshwater is already a political conflict issue in many regions of the world and threatens to lead to military confrontations.