Answer:
When two or more substances, that do not react chemically, are blended together,
the result is a mixture in which each component retains its individual identity and
properties.
The separation of the components of a mixture is a problem frequently encountered
in chemistry. The basis of the separation is the fact that each component has a
different set of physical and chemical properties. The components are pure substances
which are either elements or compounds. Under the same conditions of pressure and
temperature, the properties of every sample of a pure substance are identical. Each
sample melts at the same temperature, boils at the same temperature, has the same
solubility in a given solvent, etc.
Although these and other characteristics can be used to identify a particular
substance, we will be concerned, in this experiment, with the separation of a mixture
into its components, not with the identification of the substances. Techniques used to
separate mixtures rely on differences in the physical properties of the components.
Techniques useful for the separation of mixtures include the following:
DISTILLATION is the purification of a liquid by heating it to its boiling point, causing
vaporization, and then condensing the vapors into the liquid state and collecting the
liquid. Separation of two or more liquids requires that they have different boiling
temperatures. All boiling temperatures can be reduced by decreasing the pressure
on the liquid.
EXTRACTION is the removal of one substance from a mixture because of its
greater solubility in a given solvent.
FILTRATION is the process of removing or "straining" a solid (the chemical term is
precipitate) from a liquid by the use of filter paper or other porous material.
DECANTING is the pouring of a liquid from a solid-liquid mixture, leaving the solid
behind.
CENTRIFUGING is the process of separating a suspended solid from a liquid by
whirling the mixture at high speed.
SUBLIMATION is the physical property of some substances to pass directly from
the solid state to the gaseous state without the appearance of the liquid state. Not
all substances possess this characteristic. If one component of a mixture
sublimates, this property may be used to separate it from the other components of
the mixture. Iodine (I2), naphthalene (C10H8, mothballs), ammonium chloride
(NH4Cl) and dry ice (solid CO2) are some substances which sublime.
CHROMATOGRAPHY is the process of separating a mixture by the distribution of
its components between two phases, one phase being stationary and the other
phase moving. Some examples of chromatography are gas chromatography, paper
chromatography, and thin-layer chromatography.
