Chemical Reactions And Equations Class 10 Notes Chemistry Science Chapter 1

What are Chemical Reactions and Equations?

  • A chemical equation is a symbolic representation that describes a chemical reaction in terms of symbol and formulae.
  • A chemical reaction is the transformation of chemical substance called reactants into another chemical substance called products. In a chemical reaction, only rearrangement of atoms takes place.
  • The substances which take part in a chemical reaction are called reactants. The reactants are written on the left hand side. The new substances produced as a result of chemical reaction are called products. The products are written on the right hand side.

Some of the symbols used in a chemical equation are :
(a) Solids (s) (b) Liquids (l)
(c) Gases (g) (d) Aqueous solutions (aq)
(a) Solids (s) (f) Precipitate formed in the reaction (↓)
(g) Direction of reaction (→) (h) Used to separate multiple reactants or products (+)
(i) Formula written above the arrow is used as a catalyst in the reaction (Pt)
(J) Triangle indicates that the reaction is being heated (△)
(k) Replaces the yield sign for reversible reactions that reach equilibrium (⇌)

Steps to balance a chemical equation :

  • (a) Write word equation.
  • (b) Then write skeletal chemical equation.
  • (c) Enclose the formula in the boxes.
  • (d) List the number of atoms of different elements present in the unbalanced equation.
  • (e) Start balancing with the compound that contains the maximum number of atoms.
  • (f) Start balancing other atoms.
  • (g) Check the correctness of the balanced equation.

Types of chemical equations

Charateristics of a chemical equation: (Flow chart)

Effects of oxidation in everyday life
  • Chemical Reaction: The transformation of chemical substance into another chemical substance is known as chemical reaction.
  • Antioxidants: These are the substance that inhibits oxidation or inhibits reactions promoted by oxygen.
  • Reactant: A chemical substance that takes part in a chemical reaction and undergoes change during a reaction.
  • Catalyst: A substance that alters the rate of a chemical reaction without undergoing any change in itself during the reaction.
  • Product: A new chemical substance formed as a result of a chemical reaction.
  • Precipitate: The solid formed as a result of a precipitation reaction.
  • Reactivity series: A new series of metals ranked in order of decreasing reactivity to displace hydrogen gas from water and acid.
  • Corrosion: An irreversible damage or destruction of material in which metals are gradually eaten up by the action of air, moisture due to a chemical or electrochemical reaction on the surface of metal.
  • Oxidation: The reaction in which addition of oxygen or removal of hydrogen takes place.
  • Rancidity: It is the process of complete or incomplete oxidation or hydrolysis of fats and oils when exposed to air, light or moisture or by bacterial action resulting in unpleasant taste and odour.
  • Reduction: The chemical reaction which involves addition of hydrogen or removal of oxygen.
  • Rusting: The slow conversion of iron into hydrated ferric oxide, in the presence of moisture and air
  • Oxidising agent: A substance which helps in oxidation but itself gets reduced.
  • Rust: A reddish or yellowish-brown flaking coating of iron oxide that is formed on iron or steel by oxidation, especially in the presence of moisture.
  • Reducing agent: A substance which helps in reduction but itself gets oxidised.
  • Redox reaction: A chemical reaction in which both oxidation and reduction takes place simultaneously