Compound& Mixtures

Compound

        It is also the form of matter which can be formed by combining two or more elements in a definite ratio by mass. It can be decomposed into its constituent elements by suitable chemical methods, e.g., water (H₂O) is made of hydrogen and oxygen in the ratio 1 : 8 by mass.

Compounds can be of two types :

(i) Inorganic compounds: Previously, it was believed that these compounds are derived from non-living sources, like rocks and minerals. But these are infact the compounds of all the elements except hydrides of carbon (hydrocarbons) and their derivatives.

(ii) Organic compounds: According to earlier scientists, these compounds are derived from living sources like plants and animals, or these remain buried under the earth (e.g., petroleum). According to modern concept, these are the hydrides of carbon and their derivatives.

Mixture

       These are made up of two or more pure substances. They can possess variable composition and can be separated into their components by some physical methods.

Mixtures may be homogeneous (when composition is uniform throughout) or heterogeneous (when composition is not uniform throughout).

Common methods for the separation of mixtures are

(a) Filtration: Filtration is the process of separating solids that are suspended in liquids by pouring the mixture into a filter funnel. As the liquid passes through the filter, the solid particles are held on the filter.

(b) Distillation: Distillation is the process of heating a liquid to form vapours and then cooling the vapours to get back the liquid. This is a method by which a mixture containing volatile substances can be separated into Its components.

(c) Sublimation: This is the process of conversion of a solid directly into vapours on heating. Substances showing this property are called sublimate, e.g., iodine, naphthalene, camphor. This method is used to separate a sublimate from non-sublimate substances.

(d) Crystallisation: It is a process of separating solids having different solubilities in a particular solvent.

(e) Magnetic separation: Tills process is based upon tbe fact that a magnet attracts magnetic components of a mixture of magnetic and non-magnetic substances. The non-magnetic substance remains unaffected. Thus. it can be used to separate magnetic components from non-magnetic components.

(f) Atmolysis: Tills method is based upon rates of diffusion of gases and used for their separation from a gaseous mixture.