Chamistry class 11 notes

 Chemistry is defined as the study of the composition,properties and interaction of matter.  Chemistry is oftencalled the central science because of its role in connectingthe physical sciences, which include chemistry, with thelife sciences and applied sciences such as medicine andengineering.Various branches of chemistry are1.1 Physical chemistryThe branch of chemistry concerned with the way in whichthe physical properties of substances depend on andinfluence their chemical structure, properties, and reactions.1.2 Inorganic chemistryThe branch of chemistry which deals with the structure,composition and behavior of inorganic compounds. All thesubstances other than the carbon-hydrogen compoundsare classified under the group of inorganic substances.1.3 Organic chemistryThe discipline which deals with the study of the structure,composition and the chemical properties of organiccompounds is known as organic chemistry.1.4 BiochemistryThe discipline which deals with the structure and behaviorof the components of cells and the chemical processes inliving beings is known as biochemistry.1.5 Analytical chemistryThe branch of chemistry dealing with separation,identification and quantitative determination of thecompositions of different substances. 2. MATTERMatter is defined as any thing that occupies spacepossesses mass and the presence of which can be felt byany one or more of our five senses.Matter can exist in 3 physical states viz. solid, liquid, gas.Solid - a substance is said to be solid if it possesses adefinite volume and a definite shape, e.g., sugar, iron, gold,wood etc.Liquid- A substance is said to be liquid, if it possesses adefinite volume but no definite shape. They take up theshape of the vessel in which they are put, e.g., water, milk,oil, mercury, alcohol etc.Gas- a substance is said to be gaseous if it neither possessesdefinite volume nor a definite shape. This is because theyfill up the whole vessel in which they are put, e.g., hydrogen,oxygen etc.The three states are interconvertible by changing theconditions of temperature and pressure as follows3.  CLASSIFICATION OF MATTER AT MACROSCOPIC LEVELLAt the macroscopic or bulk level, matter can be classified as(a) mixtures (b) pure substances.

These can be further sub-divided as shown below(a)Mixtures :  A mixture contains two or more substancespresent in it (in any ratio) which are called itscomponents. A mixture may be homogeneous orheterogeneous.Homogeneous mixture- in homogeneous mixture thecomponents completely mix with each other and itscomposition is uniform throughout  i.e it consist of onlyone phase. Sugar solution and air are thus, the examples ofhomogeneous mixtures.Heterogeneous mixtures- In heterogeneous mixture thecomposition is not uniform throughout and sometimes thedifferent phases can be observed. For example, grains andpulses along with some dirt (often stone) pieces, areheterogeneous mixtures.Any distinct portion of matter that is uniform throughoutin composition and properties is called a Phase.(b)Pure substances :- A materialcontaining only onesubstance is called a pure substance.In chemistry, a substance is a form of matter that hasconstant chemical composition and characteristicproperties.  It cannot be separated into components byphysical separation methods, i.e. without breakingchemical bonds. They can be solids, liquids or gases.Pure substances can be further classified into elementsand compounds.Element- An element is defined as a pure substance thatcontains only one kind of particles. Depending upon thephysical and chemical properties, the elements are furthersubdivided into three classes, namely (1) Metals (2) Non-metals and (3) Metalloids.Compound- A compound is a pure substance containingtwo or more than two elements combined together in a fixedproportion by mass. Further, the properties of a compoundare completely different from those of its constituentelements. Moreover, the constituents of a compoundcannot be separated into simpler substances by physicalmethods. They can be separated by chemical methods. 4. PROPERTIES OF MATTEREvery substance has unique or characteristic properties.These properties can be classified into two categories –physical properties and chemical properties.4.1 Physical PropertiesPhysical properties are those properties which can bemeasured or observed without changing the identity or thecomposition of the substance. Some examples of physicalproperties are color, odor, melting point, boiling point,density etc.4.2 Chemical propertiesChemical properties are those in which a chemical changein the substance occurs. The examples of chemical propertiesare characteristic reactions of different substances; theseinclude acidity or basicity, combustibility etc.  5. MEASUREMENT5.1 Physical quantitiesAll such quantities which we come across during ourscientific studies are called Physical quantities. Evidently,the measurement of any physical quantity consists of twoparts