DEFINITIONS AND KEY POINTS

TERMS DEFINITIONS
Matter Anything that occupies space and               has mass is called
Mass The amount of matter in an object is called Mass
Element The     chemical      substances     that     in   ordinary     chemical

reactions cannot break down into simpler units are called element.

 

 

  fitom The smallest part of an element that can enter into a chemical reaction is called atom.
, Atomic

number

The atomic number of an element is the                    number of

protons in the nucleus of one of its atoms.

  Atomic

mass

The atomic mass is equal to the number of neutrons and protons in the atom’s nucleus.
  Isotopes The different forms with the same atomic number but different atomic masses are isotopes.
E shell

ergy level or

The   electrons     of   an   atom    are   distributed     around     its

nucleus in orbital called energy-level shells or clouds of

electrons              .

  Compound A compound is composed of atoms of two or more elements chemically united in fixed proportions.
  Covalent

bond

The chemical bond formed by the sharing of electrons is called covalent bond.
  Hydrogen

bonding

,

The       electrostatic        force      of      attraction         between


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electronegative     atom     and  partially    positively      charged
hydrogen atom is called hydrogen boding.

  Hydrogen

bonding

The       electrostatic        force      of      attraction         between

electronegative     atom     and  partially    positively      charged
hydrogen ‘atom is called hydrogen boding.

  Electrolytes A substance that conducts electricity in solution form is called electrolytes.
Bu er The substance which resists change in pH is called buffer.
Ca tohydrates Polyhydroxy aldehyde or ketones are called carbohydrate.
Lipids   Lipids are nonpolar organic molecules that are insoluble in polar water but soluble in nonpolar organic solvents like

ether, alcohol, and chloroform.                                      •

Fatty acids Fatty acids contain long hydrocarbon chains bonded to,. carboxyl (COOH) groups.
Fats   Fats are esters of fatty acids and glycerol.

 

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