Chemical Classification of Matter

On the basis of chemical composition,matter can be classified as

Element

*Robert Boyle was the first scientist to use the term element in 1661.

*An element is that fundamental matter which is composed of only   one kind of atoms.

*There are 118 elements out of which 98 are naturally       occurring and rest are artificially made.

*Element can be divided into metals,non-metals and metalloids.

Compound

*A compound is a pure substance composed of two or more elements,chemically combined with  one another in a fixed proportion.e.g.,water methane sugar salt.

*Compound can be broken down into its elements by chemical or electrochemical reactions,but not by any physical process.

*Compound can be categorized to organic(those with C as main constituent) and inorganic(those in which C is not main constituent).

Mixture

*Most of the matter present around us exist in the form of mixtures of two or more pure components.thus mixtures are impure substances and do not have constituents in fixed proportion.e.g.,air,sea water.

Types of mixture

Homogeneous Mixtures these mixtures have a uniform composition throughout.e.g.,salt in water,sugar in water,soft            drinks,toothpaste.

Heterogeneous Mixtures these mixtures contain physically distinct  parts and have non-uniform compositions.Mixtures of sodium chloride and iron fillings.dust particles in air,oil and water.

Separating the Components of a Mixture

Evaporation We can separate the volatile components(solvent) from its non-volatile components(solute) by method of evaporation.e.g., recovery of salt from sea water.

Centrifugation It is a process that involves use of centrifugal force for sedimentation of heterogeneous mixture.the principle is that the denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly.

           In diagnostic laboratories for blood and urine tests.

           In diaries and home to separate butter from cream.

           In washing machines to squeeze out water from wet clothes.

By the use of Separating Funnel

We can separate a mixture of two immiscible liquids by the use of separating funnel.The principle is that immiscible liquids separate out in layers depending upon their densities.

                    It is used to separate of oil and water.

Sublimation By this process,The mixture of those solids is separated in which one solid is sublimate.In this process,the mixture is heated due to which the sublimate substance is vaporized and the vapours are collected and cooled down to get the pure solid.

Naphthalene,camphor,benzoic acid,dry ice can be separated by this technique.

Chromatography It is used for separation and purification of organic compounds and its applicable for those mixtures,components of which have different adsorption capacities.It is used to separate colours in dye,drugs from the blood and cloured components of black ink.

Distillation It is based on the difference in the boiling points of the liquids in the given mixture.on boiling,liquids having lower boiling point vaporises first and collected separately.choloroform and aniline,acetone and water are separated by this process.
Fractional distillation To separate a mixture of two or miscible      liquids for which the difference in boiling points is less than 25K.

Crystallisation This method is used to purify solids.It is a process that separates a pure solid in the form of its crystals from a solution.