Page 142 - ICSE Chemistry 8

Displacement reac on: A chemical reac on in which an element takes the place of another element in a
compound
Double displacement
reac on: A chemical reac on in which two compounds react by exchange of ions to form
two new compounds
Precipita on reac on: A chemical reac on in which an insoluble solid called precipitate separates from
the solu on

Neutralisa on reac on: A chemical reac on in which an acid reacts with a base to form salt and water
Redox reac on: A chemical reac on in which oxida on and reduc on take place simultaneously

Oxida on: The addi on of oxygen or the removal of hydrogen from a substance
Reduc on: The addi on of hydrogen or the removal of oxygen from a substance
Oxidising agent: An atom or a group of atoms which accepts electrons during an oxida on reac on

Reducing agent: An atom or a group of atoms which loses electrons during a chemical reac on
Reac vity or ac vity
series of metals: The arrangement of metals in a ver cal column in the order of their decreasing
reac vity
Oxide: A compound which consists of oxygen as an anion

Calcina on: A decomposi on process in which a metallic ore is heated in the absence or limited
supply of air
Roas ng: A decomposi on process in which a metallic ore is heated in the presence of air at
a very high temperature
Acidic oxides: Oxides formed when non-metals are heated in the presence of oxygen

Basic oxides: Oxides formed when metals react with oxygen on hea ng or without hea ng
Amphoteric oxides: Oxides that can react with both acids and bases to form salt and water

Neutral oxides: Oxides which do not exhibit either acidic or basic proper es

Quick Review

• A chemical change involves the rearrangement of atoms that takes place between the reac ng
substances to form new substances having en rely diff erent proper es.
• In addi on to the forma on of new substances, a chemical change may be accompanied by one or
more of the following changes such as evolu on of gas, change of colour, forma on of precipitate,
change of state and change in energy.
• Depending upon the absorp on or evolu on of heat, chemical reac ons are of two types: exothermic
reac on and endothermic reac on.
• There are certain condi ons required for chemical reac ons to take place. These condi ons are close
contact between reactants, presence of solu on, heat energy, light energy, electricity, pressure and
catalyst.
• Catalysts are of two types: posi ve catalyst and nega ve catalyst.

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