Chemistry Introduction
Importance and scope of Chemistry
Chemistry is the branch of science which deal with the study of composition, properties and interaction of matter. In other way , chemistry is also considered as science of atoms and molecules . Chemistry has helped us to meet with our requirement that are necessary for the amelioration of life such as food additives , heath care products , plastic ,dyes , polymers etc. ,absence of which would our life very dull and dreary. Thus ,chemistry is arguably the most important branch of science.
Matter
Matter is anything which possesses mass and occupies space. Matter can generally exist in three physical states viz solid liquid and gas. The particles have space between them, called the intermolecular space.
Classification of Matter
Matter can be classified by two ways on the basis of :
(1) Physical state
On the basis of physical state , matter may be classified into solid, liquid and gas under the conditions of ordinary temperatures and pressures , Solids have a definite volume and shape, liquids have definite volume but do not have definite shape while, gases neither have a definite volume nor a definite shape.
(2) Chemical classification
Matter can also be classified on the basis of chemical composition and properties. On the basis , matter can be classified as
Pure Substance
These have fixed composition and non- variable properties. These cannot be separated into simpler substances by physical methods.
(a) Elements
Pure substances which consist of only one type of atom. e.g. Na , Mg , Al etc.
(b) Compounds
Pure substances that are composed of two or more types of atom , i.e. here different elements are present in fixed proportion by mass.
Proportion of a compound are different from the properties of the constituent elements . e.g H2o, NH3, NaCl etc
Mixtures
These are the combinations of two or more substances (elements or compounds) which are not chemically combined together and retain their characteristic properties .These may be separated into pure components by applying physical methods.
Mixture are of two type :
(a) Homogeneous mixture
These mixture have uniform composition throughout and components are distinguishable. e.g. a liquid solution of sugar and water etc.
(b) Heterogeneous mixture
These mixture do not have uniform composition throughout and components are distinguishable. e.g. a mixture of sand and salt etc.
Properties of Matter
Every substance has its characteristic properties . These properties are of the following two types :
(1) Physical properties
These properties can be measured without change in composition of substance.
e.g. mass, length, temperature density etc.
(2) Chemical properties
Measurement of these properties require chemical change in substance.
e.g. acidity, basicity , combustibility etc.
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