What is Chemistry ? - NCERT based Chemistry notes
BASIC CONCEPTS OF CHEMISTRY -
" chemistry is the science of molecules and their transformations. It is the science not so much of the one hundred elements but of the infinite variety of molecules that may be built from them." Roald Hoffmann
OR "Chemistry may be defined as the branch of science which deals with the study of matter ,its composition,its properties and the change which it undergoes in composition as well as in energy during various processes."
In simple words we can understood it by the examples, that every thing around us is related to chemical science or chemistry. e.g.-pen, ink, furniture, human, animals, electronics, cloths, bags etc. everything made by group of atoms, molecules and compounds.
Everything in this world have some composition.Here we can also understood the reactions by some daily life examples;-curd formation by milk,icing from water,fire from burner ,light from bulb etc.Now here we are going to study about chemistry in which we can learn all about the atoms, molecules and compounds.
DEVELOPMENT OF CHEMISTRY-
Basic concepts of chemistryChemistry :-What is chemistry?
People of india already had knowledge about many chemical phenomenon and Chemistry mainly developed in 1300-1600 CE.Modern chemistry also took shape in 18th century europe. Copper utensils,iron,gold,silver ornaments found in many archeological sites in north india.
The indian novels e.g. Sushruta samhita tell us about the impotance of alkalies,Charaka Samhita mentions ancient indians who knew how to prepare sulphuric acid,nitric acid and oxides of copper,tin and zinc,the sulpahtes of copper,zinc and iron and the carbonates of lead and iron, Rasopanishada explain us about gunpowder mixture,Tamil texts also describe about the preparation of fireworks using sulphur,charcoal,saltpetre(potassium nitrate),mercury,camphor etc. So via the above discussion we can better understood in terms of basic constituents of matter that are atoms and molecules.so that's why chemistry is also called the science of atoms and molecules.now there are some questions arrises in our mind i.e.-
- Can we see the atoms & molecules?
- Can we weigh the molecules and atoms?
- Can we count the number of atoms or molecules in any compound?
- Is there any relationship between atoms, molecules and compounds?
- How physical properties of matter can be quantitatively described?
Now chemistry is further divided into various branches which is depends upon various feilds of study.Mainly the various branches of chemistry are;-
- (1) Inorganic chemistry
- (2) Organic chemistry
- (3) Physical chemistry
- (4) Analytical chemistry
- (5) Industrial chemistry
- (6) Bio chemistry
- (7) Nuclear chemistry etc.
Importance of chemistry :-
In our daily life,chemistry plays a very important role and We use many chemical products which also contribute to national economy so here are some major chemical products or fields of chemistry which is given below;-
- (1)Chemistry in Medicines- you can understood it by some medicinal examples that is;- taxol and cisplatin is used in cancer treatment, azedothymidine (AZT) used in aiids treatment.
- (2)Chemistry in Agriculture- e.g.-chemical fertilizer,insecticides,preservatives etc.
- (3)Chemistry in industries- pharmaceutical companies,polybag companies,cement,glass,ornaments etc.
- (4)Chemistry in domestic life- soap,phenyl,creams,oils,detergent and colors etc.
- (5)Chemistry in film industry- films made up of celluloid coated with suitable chemicals etc.
- (6)Chemistry in energy sources- coal,petrolium,nuclear fuels,solar panels etc.
Nature of Matter
Nature of matter can easily understood by our daily life.Here, we can see many objects and can feel various senses like sight, taste, hearing, touch and smelling. These objects possesses mass, occupy space and may have different shapes, sizes and colors.All these objects made by matter.
"Matter can be defined as anything that occupies space, possesses mass, offer resistance and can be felt by one or more of our senses."We can better understood it by some examples like; water, air, metals, plants, animals etc.
Now matter can divided depending upon physical or chemical nature-
(1) PHYSICAL CLASSIFICATION OF MATTER - On the basis of physical nature, we can classify it as -
- Solid - e.g; rocks, glass, wood, ornaments, pencil etc.
- Liquid -e.g; water, milk, tea, ink etc.
- Gas -e.g; oxygen, hydrogen, nitrogen etc.
It can be better explained or understood with the help of below given table with differentiation -
Solid
(1) Particles are closely packed(RIGID) but not able to freely move.
(2) Have definite shape and volume
(3) Have 2 or more surfaces
(4) Have melting and sublimation points
(5) Can convert into liquid and gas on heating
Liquid
Particles are less closely packed(Less rigid) and able to move around
Have definite volume but different shape
Have only one surface
Have boiling and freezing points
Can convert into gas on boiling and convert into solid on freezing
Gas
Particles are far away and can freely move throughout
. No definite shape nor volume
Have no surface
. Have only freezing point
Can convert into liquid and solid on freezing
(2) CHEMICAL CLASSIFICATION OF MATTER - On the basis of chemical nature, we can classify it as -
(A) ELEMENTS -"An element can be defined as pure substance which is made of one kind of atom."
- Can not be decomposed further in simple substances
- Only have one kind of atoms
- Can be further divided into 3 parts - (a) metals (b) non metals (c) metalloids
(B) COMPOUNDS - "A compound may be defined as a pure substance which can be decomposed into simpler substances by some suitable chemical method. A compound is formed by combination of two or more elements in a definite proportion by mass."
- Can be decomposed further in simple substances
- Have two or more kind of atoms
- Constituent elements do not retain their properties
- They can further divided in two parts- (a) organic compounds (b) inorganic compounds
(C) HOMOGENEOUS MIXTURE - "A mixture which have same composition throughout." and not distinguishable in a mixture.
(D) HETEROGENEOUS MIXTURE - "A mixture which have different composition in a particular place or object." and distinguishable in a mixture.
DIFFERENTIATION TABLE BETWEEN COMPOUND AND MIXTURE
| Compound | Mixture |
| The constituents of a compound are always present in a fixed ratio by mass. | The constituents of a mixture may be present in any ratio. |
| The properties of a compound are different from those of its constituent elements. | Properties of a mixture are midway between those of its constituents. |
| Compound is always homogeneous in nature | Mixture may or may not be homogeneous in nature. |
| Chemical compounds possess sharp melting and boiling points. | The melting and boiling points of mixtures are usually no sharp |
| The constituents of a compound cannot be easily separated by simple mechanical mean. Energy in the form of heat or light is often required | The constituents of a mixture can be easily separated by simple mechanical means. |
| Compounds are formed as a result of a chemical change. | Mixtures are formed as a result of a physical change |
| Formation of compound is always accompanied by absorption or evolution of heat, light or electrical energy. | When mixture is formed, no heat, light or electrical energy is absorbed or evolved |
Comments
Post a Comment