Solvent Evaporation, Crystallization

Forming Solids from Solutions Under certain conditions, a solute can come back out of its solution and form a solid. This process is called crystallization. Sometimes this occurs when the solution is cooled or when some of the solvent evaporates. Crystallization is the result of a physical change. When some solutions are mixed, a chemical reaction occurs, forming a solid. This solid is called a precipitate (prih SIH pub tayt). A precipitate is the result of a chemical change. Precipitates probably have formed in your sink or shower because of chemical reactions. Minerals that are dissolved in tap water react chemically with soap. The product of this reaction leaves the water as a precipitate called soap scum, shown in Figure 3. 

Crystallization from a solution is a thermal separation process. A solution of one or more solids molecularly dispersed in a solvent is usually concentrated by multistage evaporation of the solvent. Since the concentrated solution becomes supersaturated by cooling ( cooling crystallization ), evaporation of solvent ( evaporation crystallization ) or flash evaporation ( vacuum crystallization a combination of cooling and evaporation) causes crystals to form and grow. To reduce the degree of supersaturation, the surplus forms a solid which... 

If only a minor temperature dependency of the solubility is observed, the solution is supersaturated by evaporation of solvent, evaporation crystallization. The saturated solution is heated from i i to i 2 where the solvent evaporates along the line 2 - 3... 

---