1. Physical Change: A change in which a substance undergoes a change in its physical properties is called physical change.
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2. Chemical change: It is the change in which identity of the substance is changed
and a new substance is formed.
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3. Signs of a chemical reaction: These factors denote that a chemical reaction has taken place- change of state of substance, change of colour of substance, evolution of heat, absorption of heat, evolution of gas and evolution of light.
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4. Chemical reactions: The transformation of chemical substance into a new chemical substance by making and breaking of bonds between different atoms is known as Chemical Reaction.
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5. Chemical equation: The representation of chemical reaction by means of symbols of substances in the form of formulae is called chemical equation.
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6. Balanced chemical equation: A balanced chemical equation has number atoms of each element equal on both left and right sides of the reaction.
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7. Combination reaction: When two elements or one
element and one compound or two compounds combines to give one single product.
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8. Decomposition reaction: Splitting of a compound into two or more simple products.
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9. Displacement reaction: It takes place when a more reactive metal displaces a
less reactive metal.
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10. Double displacement reaction: Reactions in which ions are exchanged between two reactants forming new compounds are called double displacement reactions.
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11. Precipitation: The insoluble compound called precipitate forms in this reaction.
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12. Exothermic: Reactions which produce energy are called exothermic reaction. Most of the decomposition reactions
are exothermic.
13. Endothermic- Reactions which absorb energy are called endothermic reaction. Most of the combination
reactions are endothermic.
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14. Oxidation: Gain of oxygen or removal of hydrogen or metallic element from a compound is known as oxidation.
15. Reduction: Addition of hydrogen or removal of oxygen from a compound is called reduction.
16. Redox reactions: A chemical reactions where oxidation and reduction both take place simultaneously are also known as redox reaction.
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17. Rusting: When Iron reacts with oxygen and moisture forms a red substance called rust.
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18. Rancidity: Oils and fats when oxidized on exposure to air show a change in taste and smell.
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19. Corrosion: Metals when attacked by oxygen, water, acids, and gases present in air changes their surface which is called corrosion.
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