Definition of Distillation:
Distillation is the technique of heating a liquid to create vapor which is collected
when cooled separate from the original liquid. Distillation is a method of
separating mixtures based on differences in their boiling points. It is a unit
operation, or a physical separation process, and not a chemical reaction.
It is a technique used by chemists to separate compounds in a mixture by boiling
point. The mixture of compounds is boiled from a still pot in a distillation
apparatus equipped with a condenser and a receiving flask. Ideally, the lighter,
lower-boiling compound will vaporize first, collect in the condenser, and drop to
the receiving flask. After the first compound has collected, the second, higher-
boiling compound will start to vaporize, condense, and collect. Material that is left
in the original still pot can be combined with fractions of collected material that
contain a mixture of compounds and resubjected to a second distillation.
Distillation is used commercially to concentrate alcohol for spirits and purify
Examples: Pure water can be separated from salt water through distillation. Salt
water is boiled to create water steam, but the salt remains in the solution. The
steam is collected and allowed to cool back into salt-free water.
Vaporization is the process that occurs when a chemical or element is converted
from a liquid or a solid to a gas. Act of vaporizing or the state of being vaporized.
When a liquid is converted to a gas, the process is called evaporation or boiling;
when a solid is converted to a gas, the process is called sublimation. Vaporization
is the transition of matter from a solid or liquid phase into a gaseous (or vapor)
phase. Water boiling into steam is an example of vaporization. Vaporization of an
element or compound is a phase transition from the liquid or solid phase to gas
phase. Vaporization is an important step in the water cycle. There are three types
of vaporization: evaporation, boiling and sublimation.
Definition of Evaporation:
Evaporation is a phase transition from the liquid phase to gas phase that occurs at
temperatures below the boiling temperature at a given pressure. Evaporation
usually occurs on the surface. It is a type of vaporization of a liquid that occurs
only on the surface of a liquid. The other type of vaporization is boiling, which,
instead, occurs on the entire mass of the liquid. Evaporation is also part of the
water cycle. On average, the molecules in a glass of water do not have enough heat
energy to escape from the liquid. With sufficient heat, the liquid would turn into
vapor quickly. When the molecules collide, they transfer energy to each other in
varying degrees, based on how they collide. Sometimes the transfer is so one-sided
for a molecule near the surface that it ends up with enough energy to 'escape'
(evaporate). Liquids that do not evaporate visibly at a given temperature in a given
gas (e.g., cooking oil at room temperature) have molecules that do not tend to
transfer energy to each other in a pattern sufficient to frequently give a molecule
the heat energy necessary to turn into vapor. However, these liquids are
evaporating. It is just that the process is much slower and thus significantly less
Definition of Boiling:
Boiling is a phase transition from the liquid phase to gas phase that occurs at or
above the boiling temperature. Boiling, as opposed to evaporation, occurs below
Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated
to its boiling point, the temperature at which the vapor pressure of the liquid is
equal to the pressure exerted on the liquid by the surrounding environmental
pressure. While below the boiling point a liquid evaporates from its surface, at the
boiling point vapor bubbles come from the bulk of the liquid. For this to be
possible, the vapor pressure must be sufficiently high to win the atmospheric
pressure, so that the bubbles can be "inflated". Thus, the difference between
evaporation and boiling is "mechanical", rather than thermodynamical. The boiling
point is lowered when the pressure of the surrounding atmosphere is reduced, for
example by the use of a vacuum pump or at high altitudes. Boiling occurs in three
characteristic stages, which are nucleate, transition and film boiling. These stages
generally take place from low to high heating surface temperatures, respectively.
Definition of Sublimation:
Sublimation refers to the process of transition of a substance from the solid phase
to the gas phase without passing through an intermediate liquid phase. Sublimation
is an endothermic phase transition that occurs at temperatures and pressures below
a substance's triple point in its phase diagram.
At normal pressures, most chemical compounds and elements possess three
different states at different temperatures. In these cases the transition from the solid
to the gaseous state requires an intermediate liquid state. Note, however, that the
pressure referred to here is the partial pressure of the substance, not the total (e.g.
atmospheric) pressure of the entire system. So, all solids which possess an
appreciable vapor pressure at a certain temperature usually can sublime in air (e.g.
ice just below 0°C). For some substances, such as carbon and arsenic, sublimation
is much easier than evaporation from the melt, because the pressure of their triple
point is very high, and it is difficult to obtain them as liquids.
Sublimation requires additional energy and is an endothermic change. The
enthalpy of sublimation (also called heat of sublimation) can be calculated as the
enthalpy of fusion plus the enthalpy of vaporization. The reverse process of
sublimation is deposition. The formation of frost is an example of meteorological
Definition of Reflux:
Reflux is a technique involving the condensation of vapors and the return of this
condensate to the system from which it originated. It is used in industrial and
laboratory distillations. It is also used in chemistry to supply energy to reactions
over a long period of time.
The term reflux is very widely used in industries that utilize large-scale distillation
columns and fractionators such as petroleum refineries, petrochemical and
chemical plants, and natural gas processing plants.
In that context, reflux refers to the portion of the overhead liquid product from a
distillation column or fractionator that is returned to the upper part of the column
as shown in the schematic diagram of a typical industrial distillation column.
Inside the column, the downflowing reflux liquid provides cooling and
condensation of the upflowing vapors thereby increasing the efficiency of the
The more reflux provided for a given number of theoretical plates, the better is the
column's separation of lower boiling materials from higher boiling materials.
Conversely, for a given desired separation, the more reflux is provided, the fewer
theoretical plates are required.
Definition of Filtration:
Filtration is used to separate particles and fluid in a suspension, where the fluid
can be a liquid, a gas or a supercritical fluid. Depending on the application, either
one or both of the components may be isolated. It is a technique used either to
remove impurities from an organic solution or to isolate an organic solid. The two
types of filtration commonly used in organic chemistry laboratories are gravity
filtration and vacuum or suction filtration.
Filtration, as a physical operation is very important in chemistry for the separation
of materials of different chemical composition. A solvent is chosen which
dissolves one component, while not dissolving the other. By dissolving the mixture
in the chosen solvent, one component will go into the solution and pass through the
filter, while the other will be retained. This is one of the most important techniques
used by chemists to purify compounds. ). Filtration is also used to describe some
biological processes, especially in water treatment and sewage treatment in which
undesirable constituents are removed by adsorption into a biological film grown on
or in the filter medium.