The process of lowering the temperature of a liquid or solid to its freezing point. At this point the item becomes solid. The temperature at which pure water freezes is 32º Fahrenheit or 0º Celsius. Impurities, minerals and miscellaneous substances in water (such as salt or alcohol) change the temperature or length of time required to freeze water. Thus, various liquid substances freeze at different temperatures based on their chemical composition. Solid items such as food also experience similar results, freezing at different lengths of time or temperatures based on their substance and chemical composition.