Types of Substances
* A change in the physical appearance but not its chemical composition is known as physical change.
* A change in which a substance changes into a chemically new substance is referred to as a chemical change.
* A substance which is made up of one kind of particle is referred to as a pure substance.
* A substance which contains two or more different kinds of particles is known as a mixture.
* An element is a substance or a piece of matter that is made of only one kind of atom.
* Elements are homogeneous in nature and are classified into metals, non-metals and metalloids.
* Metals are lustrous, good conductors of heat and electricity, malleable, ductile, sonorous and are solids except mercury.
* Non-metals are non-lustrous, bad conductors of heat and electricity, not malleable, non ductile, non sonorous and exists in all three states.
* The elements which have intermediate properties between those of metals and nonmetals are called metalloids.
* Compound is a pure substance made of atoms of two or more elements that are chemically bound together.
* Compounds have fixed composition with sharp melting and boiling points.
* Matter that consists of two or more substances mixed together, but not chemically combined is known as mixture.
* Mixtures have variable composition.
Types of Mixtures
* A solution is a homogeneous mixture of two or more substances.
* The component of the solution that is present in a larger amount is called the solvent.
* The component of the solution that is relatively present in a smaller quantity is called the solute.
* Concentration is defined as the amount of solute present in unit volume of a solution.
* A solution in which no more solute will dissolve is called a saturated solution.
* A solution in which more of the solute will dissolve is an unsaturated solution.
* Solubility is the maximum amount of solute by weight in grams dissolved in 100 grams of solvent at a constant temperature.
* A suspension is a heterogeneous mixture in which the solute particles do not dissolve and remain suspended.
* A colloid is a heterogeneous mixture in which the particles cannot be seen with the naked eye.
* The dispersed particles in a colloid form the dispersed phase.
* The component in which the dispersed phase is suspended is known as the dispersing medium.
* The phenomenon of the scattering of light by colloidal particles is called the Tyndall effect.
Methods of Separation of Mixtures
* To separate a mixture in which one of the components is attracted to a magnet, pass a magnet over the mixture.
* Evaporation is used to separate a mixture containing a solute and a solvent by evaporating the solvent.
* Filtration is used to remove insoluble solids from a liquid.
* Centrifugation is used to separate a mixture of a solid and a liquid in which the particles of the solid are very small.
* Two immiscible liquids can be separated by using a separating funnel.
* A mixture that contains a salt and a sublimate can be separated by using the process of sublimation.
* Chromatography is used to separate a mixture that comprises solutes that dissolve in the same solvent.
* Distillation is used for the separation of a mixture of two miscible liquids that boil without decomposing and have a large difference between their boiling points.
Fractional distillation is used:
* To separate a mixture of liquids when the difference between the boiling points is less than 25 Kelvin temperature
* To separate the components of air
* Crystallisation is used to purify solids.
