Thursday, 15 March 2018

Some basic concept of Chemistry notes - 1 for dmlt and paramedical students

What is chemistry ?

Chemistry is the science of molecules and their transformations. Chemistry is called the science of atoms and molecules.
Chemistry is the branch of science that studies the composition, properties and interaction of matter.

what is the importance of chemistry?

(1) Chemistry plays an important role in meeting human needs for food, health care products and other materials
(2) Production of a variety of fertilizers, improved varieties of pesticides and insecticides
(3) Preparation of drugs isolated from plant and animal sources or prepared by synthetic methods.
(4) Design and synthesize new materials having specific magnetic, electric and optical properties.
(5) Production of superconducting ceramics, conducting polymers, optical fibres and large scale miniaturization of solid state devices.

What is matter
Anything which has mass and occupies space is called matter.

 for example, book, pen, pencil, water, air, all living beings etc. are composed of matter.

Classification of matter: 

The matter can exist in three physical states viz. solid, liquid and gas.

Solid : Solids have definite volume and definite shape. Reason In solids, these particles are held very close to each other in an orderly fashion and there is not much freedom of movement.

Liquid Liquids have definite volume but not the definite shape. They take the shape of the container in which they are placed.
Reason In liquids, the particles are close to each other but they can move around

Gas: Gases have neither definite volume nor definite shape. They completely occupy the container in which they are placed.

Reason :in gases, the particles are far apart as compared to those present in solid or liquid states and their movement is easy and fast.

Matter can be classified based on chemical state. 

Mixture : A mixture contains two or more substances present in it (in any ratio) which are called its components.
 For example, sugar solution in water, air, tea etc.

Mixtures are two types:

homogeneous mixtures :
 the components completely mix with each other and its composition is uniform throughout.

Examples Sugar solution, air 

heterogeneous mixtures: 
the composition is not uniform throughout and sometimes the different components can be observed.

Example: mixtures of salt and sugar

Pure substances: They have fixed composition . constituents components of pure substances cannot be separated by simple
physical methods. 

Examples Copper, silver, gold, water, glucose etc 

Pure substances can be further classified into 

                         elements and compounds 

Elements: 
An element consists of only one type of particles. These particles may be atoms or molecules. Examples: Sodium, copper, silver, hydrogen, oxygen etc. 

Compound: 
When two or more atoms of different elements combine, the molecule of a compound is obtained.
the properties of a compound are different from those of its constituent elements. 
Constituent particles can be separated by chemical methods

The examples of some compounds are water, ammonia, carbon dioxide, sugar etc 

What are the physical properties of the matter? 

Physical properties are those properties which can be measured or observed without changing the identity or the composition of the substance. 
Examples: colour, odour, melting point,boiling point, density etc.

What are the chemical properties? 

The chemical properties are those properties which require a chemical changes to occurs. 
Examples: acidity or basicity, combustability.

                  To be Continue.... 

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