Page 62 - ICSE Chemistry 8

Crystallisa on: A process of separa ng a solid that has dissolved in a liquid and made a solu on
Froth fl oata on: A separa on technique based on the principle of we ng of compounds of a mixture
Sublima on: A process by which a substance changes directly from the solid state to the liquid
state without passing through the intermediate liquid state
Dis lla on: A process of separa ng a liquid from a soluble component by selec ve evapora on
Dis lla on fl ask: A special round bo om fl ask used to perform dis lla on
Centrifuga on: A process of separa ng fi nely suspended solid components in a liquid by spinning
the mixture in a closed container

Centrifuge: A machine in which the spinning of a mixture occurs
Separa ng funnel: A laboratory equipment made up of glass with a tap called stopcock
Frac onal dis lla on: A process of separa ng a mixture into its components or frac ons by hea ng the
mixture
Chromatography: A process of separa ng diff erent components of a mixture by passing it through a
medium in which the components move at diff erent rates

Quick Review
• Ma er is anything that has mass and occupies space.
• Ma er can be broadly classifi ed into two categories: pure substances and mixtures. Pure substances
are further classifi ed as elements and compounds.
• A pure substance has a defi nite composi on, and has defi nite mel ng and boiling points.
• A mixture has no defi nite composi on, and has no defi nite mel ng and boiling points. The cons tuents
of a mixture can be separated by simple physical methods and the original proper es of cons tuents
of a mixture are retained. A mixture has no fi xed physical and chemical proper es. There is no energy
absorbed or released during the forma on of a mixture.
• Mixtures can be classifi ed as homogeneous and heterogeneous.
• Heterogenous mixtures are found in the form of suspensions or emulsions.
• Diff erent mixtures can be formed on combining diff erent states of ma er.
• There are various types of mixtures such as solid-solid mixture, solid-liquid mixture, solid-gas mixture,
liquid-liquid mixture, liquid-gas mixture and gas-gas mixture.
• There is another type of mixture called alloy which is a metallic mixture of a metal with another metal
• Mixtures are combina ons of two or more pure substances that come in several forms. Most of the
mixtures can be separated depending on the kind of mixture it is.
• The separa on of mixtures becomes essen al to obtain a useful component, to obtain a pure sample of
a substance and to enhance purity of a substance, and to remove harmful and undesirable impuri es.

• The basis of separa on of a mixture is the fact that each component of a mixture has diff erent physical
and chemical proper es.
• The various techniques used for separa on of mixtures are handpicking, sieving, winnowing, magne c
separa on, gravita on, solvent extrac on, frac onal crystallisa on, sedimenta on and decanta on,
fi ltra on, evapora on, crystallisa on, froth fl oata on, sublima on, dis lla on, centrifuga on, using a
separa ng funnel, frac onal dis lla on and chromatography.
• A combina on of methods can be used when a mixture consists of more than two components.

48