Compounds                                              process of “dissolving out” from the solution
                                                       as the solvent evaporates.
    It composed of two or more different
     atoms chemically bonded to one another.           Distillation is the process of heating a solution
    It can be destroyed by chemical means.            containing soluble solids to form vapours of
    It might be broken down into simpler              the liquid and then cooling the vapours to get
     compounds, into its elements or a                 the liquid back.
     combination of the two.
                                                       Sublimation is a process in which some
    For example, water (H2O) is a compound
                                                       solids, on heating, are transformed directly to
     made up of two elements, hydrogen (H)
                                                       vapour without passing through the liquid
     and oxygen (O).
                                                       phase, and vice versa. This technique can be
    Compounds are divided into two main
                                                       used to separate a mixture of solids, one of
     categories: Organic compounds and
                                                       which can undergo sublimation. The vapours
     Inorganic compounds.
                                                       are then cooled separately to get the sublimed
Mixtures or Impure Substances                          solid back.
    It is a material system made up of two or         Extraction is the process of dissolving out the
     more different substances which are mixed         soluble component from a mixture, and
     but are not combined chemically.                  subsequently treating the solution to get the
                                                       solid.
    Homogeneous mixture : It is relatively
     uniform in composition; every portion of          Magnetic separation is exemplified by the
     the mixture is like every other portion.          separation of iron filings.
    Heterogeneous mixture : It is a mixture
     whose composition varies from position to         Chromatography is an advanced technique of
     position within the sample.                       separation in which individual components of
                                                       a mixture are separated from each other using
VARIOUS SEPARATION PROCESSES                           the property of differential migration (different
OF MIXTURES                                            rates of flow).
Sedimentation is the process of separating an          Fractional distillation is the process of
insoluble solid from a liquid in which it is           separating two or more miscible liquids by a
suspended by allowing it to settle to the              modified distillation process, in which the
bottom of the container. If this also involves         distillates are collected as fractions having
pouring off of the liquid leaving the solid            different boiling points. The separation of the
behind, it is called decantation.                      liquids by this method is based on the
                                                       difference in their boiling points.
Filtration is used for separating insoluble
solids from a liquid.                                  Reverse Osmosis (RO) is the process of
                                                       forcing a solvent from a region of high solute
Evaporation is used for recovering dissolved
                                                       concentration through a semipermeable
solid substances from solutions by evaporating
                                                       membrane to a region of low solute
the solvent. The solute “dissolves out” and is
                                                       concentration by applying a pressure in excess
left behind.
                                                       of the osmotic pressure.
Crystallisation is a sophisticated form of
evaporation technique in which crystals of the
solute are encouraged to develop during the
                                                  257