CBSE Class 11 Chemistry Revision Notes Set D

 SOME BASIC CONCEPTS OF CHEMISTRY Chemistry:

Chemistry is the branch of science that deals with the composition, structure and properties of matter. Chemistry is called the science of atoms and molecule .

Branches of Chemistry

Organic Chemistry -This branch deals with study of carbon compounds especially hydrocarbons and their derivatives.

Inorganic Chemistry-This branch deals with the study of compounds of all other elements except carbon. It largely concerns itself with the study of minerals found in the Earth's crust.

Physical Chemistry-The explanation of fundamental principles governing various chemical phenomena is the main concern of this branch. It is basically concerned with laws and theories of the different branches of chemistry.

Industrial Chemistry-The chemistry involved in industrial processes is studied under this branch.

Analytical Chemistry-This branch deals with the qualitative and quantitative analysis of various substances.

Biochemistry-This branch deals with the chemical changes going on in the bodies of living organisms; plants and animals.

Nuclear Chemistry-Nuclear reactions, such as nuclear fission, nuclear fusion, transmutation processes etc. are studied under this branch. 

PROPERTIES OF MATTER AND THEIR MEASUREMENT--

Every substance has unique or characteristic properties. These properties can be classified into two categories – physical properties and chemical properties.

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

The measurement or observation of chemical properties requires a chemical change to occur. e.g. Burning of Mg-ribbon in air .

Chemical properties are characteristic reactions of different substances; these include acidity or basicity, combustibility etc.Many properties of matter such as length, area, volume, etc., are quantitative in nature.

Metric System was based on the decimal system.

The International System of Units (SI) The International System of Units (in French Le Systeme International d’Unites– abbreviated as SI) was established by the 11th General Conference on Weights and Measures (CGPM from ConferenceGenerale des Poids at Measures). The SI system has seven base units

Mass and Weight-- Mass of a substance is the amount of matter present in it while weight is the force exerted by gravity on an object. The mass of a substance is constant whereas its weight may vary from one place to another due to change in gravity. The mass of a substance can be determined very accurately by using an analytical balance

Volume-- Volume has the units of (length)3. So volume has units of m3 or cm3 or dm3.A common unit, litre (L) is not an SI unit, is used for measurement of volume of liquids. 1 L = 1000 mL, 1000 cm³ = 1 dm³

Density: Density of a substance is its amount of mass per unit volume.SI unit of density = SI unit of mass/SI unit of volume = kg/m3 or kg m^–3This unit is quite large and a chemist often expresses density in g cm^–3.

Temperature--There are three common scales to measure temperature — °C (degree celsius), °F (degree Fahrenheit) and K (kelvin). Here, K is the SI unit.

⁰F = 9/5(C⁰) +32

K = °C + 273.15 Note—Temperature below 0 °C (i.e. negative values) are possible in Celsius scale but in Kelvin scale, negative temperature is not possible.

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