To separate substance components from homogeneous mixtures, we use methods called fractionation, which are based on temperature constancy in changes in physical states. They are: distillation and fusion.
It consists of separating liquids and solids with different boiling points. The liquids must be miscible with each other.
Example: water + ethyl alcohol; water + cooking salt
The boiling point of water is 100 ° C and the boiling point of ethyl alcohol is 78 ° C. If we heat this mixture, the alcohol boils first.
In the condenser, the alcohol vapor is cooled and made into liquid alcohol, passing to another container, which may be a collecting flask, an erlenmeyer flask or a beaker glass. And the water remains in the previous container, thus separating from the alcohol.
For this technique, the apparatus called distillers is used, which is a set of glassware of the chemical laboratory. Used: thermometer, distillation flask, metal rod or holder, Bunsen nozzle, condenser, hoses, grippers and collecting bottle. This method is called simple distillation.
In industries, mainly oil, fractional distillation to separate mixtures of two or more liquids. The oil separation towers make their division producing gasoline, diesel oil, natural gas, kerosene, tar.
Substances should have different boiling points, but with values close to each other.
Separates components from homogeneous mixtures of various solids. The solid substance is melted to its melting point, separating from the other substances.
Example: solid mixture between tin and lead.
Tin melts at 231 ° C and lead at 327 ° C. Then the tin first melts.