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CBSE Science Chap 1 - Chemical Reactions and Equations

Chapter Summary

 

  • A complete chemical equation represents the reactants, products and their physical states symbolically.
  •  A chemical equation is balanced so that the numbers of atoms of each type involved in a chemical reaction are the same on the reactant and product sides of the equation. Equations must always be balanced.
  • In a combination reaction two or more substances combine to form a new single substance.
  • Decomposition reactions are opposite to combination reactions. In a decomposition reaction, a single substance decomposes to give two or more substances.
  • Reactions in which heat is given out along with the products are called exothermic reactions.
  •  Reactions in which energy is absorbed are known as endothermic reactions.
  • When an element displaces another element from its compound, a displacement reaction occurs.
  • Two different atoms or groups of atoms (ions) are exchanged in double displacement reactions.
  • Precipitation reactions produce insoluble salts.
  •  Reactions also involve the gain or loss of oxygen or hydrogen by substances.
  • Oxidation is the gain of oxygen or loss of hydrogen. Reduction is the loss of oxygen or gain of hydrogen.

NCERT Book Solutions


 

 

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