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NEET Chemistry Some Basic Concepts in Chemistry

Some Basic Concepts in Chemistry PDF Notes, Important Questions and Synopsis


Basic Concepts of Chemistry

Classification of Matter:

Properties of Matter:
Physical properties: Colour, odour, melting point, boiling point, density
Chemical properties: Acidity, basicity, combustibility

The International System of Units (SI):

Physical quantity

  Symbol for quantity

        Name of SI unit

      Symbol for SI unit













   Electric current




Thermodynamic temperature




Amount of substance




Luminous intensity




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.
  • Thermometer with the Celsius scale is calibrated from 0 to 100.
  • The Fahrenheit scale is represented between 32 and 212.
  • Negative values of temperature are not possible on the Kelvin scale.
Significant figures:
  • Significant figures are meaningful digits which are known with certainty.
Laws of Chemical Combination
  • Law of conservation of mass: Matter can neither be created nor be destroyed.
  • Law of definite proportions: given compound always contains the same proportion of elements by weight.
  • Law of multiple proportions: If two elements can combine to form more than one compound, the masses of one element which
    combine with a fixed mass of the other element are in the ratio of small whole numbers.
  • Gay-Lusaac’s law of gaseous volumes: When gases combine or are produced in a chemical reaction, they do so in a simple ratio by volume provided all gases are at the same temperature and pressure.
  • Avogadro’s law: Equal volumes of gases at the same temperature and pressure should contain equal number of molecules.
Atomic mass
  • One atomic mass is defined as mass exactly equal to 1/12th the mass of one carbon-12 atom.
Molecular mass
  • Molecular mass is the sum of atomic masses of the element present in the molecule.
Formula mass
  • The formula mass of a molecule is the sum of the atomic weights of the atoms in the empirical formula of a compound.


  • One mole is the amount of substance which contains as many particles or entities as there are atoms in exactly 12 g of the C-12 isotope.
Molar mass
  • The mass of one mole of a substance in grams.
Empirical formula and molecular formula
  • An empirical formula represents the simplest whole number ratio of various atoms present in a compound.
  • A molecular formula shows the exact number of different types of atoms present in a molecule of a compound.


  • Stoichiometry deals with the relationship between reactants and products involved in a chemical reaction to determine desired quantitative data.

Limiting reagent

  • A limiting reagent in a chemical reaction is a substance which is totally consumed when the reaction is completed.
Concentration terms
  • Molarity (M): Number of moles of a solute present in per unit volume of solution.
  • Molality (m): Number of moles of a solute present in one kilogram of a solvent.
  • Normality (N): Number of gram equivalents of a solute present in per unit volume of solution.
  • Mole fraction: Ratio of the number of moles of a particular component to the total number of moles of the solution.
  • Mass per cent or weight per cent (w/w%): Gram of solute present in 100 gram of solution.
  • Volume by volume per cent (v/v%): mL of solute present in 100 mL of solution.
  • Weight by volume per cent (w/v%): Gram of solute present in 100 mL of solution.