RBSE Class 10 Science Notes Chapter 1 Chemical Reactions and Equations

These comprehensive RBSE Class 10 Science Notes Chapter 1 Chemical Reactions and Equations will give a brief overview of all the concepts.

RBSE Class 10 Science Chapter 1 Notes Chemical Reactions and Equations

→ Chemical Reaction – When a substance reacts with itself or any other substance to form a substance with one or more new chemical properties, then this is called a chemical reaction.

→ Chemical Equation – Representation of a chemical reaction by the use of symbols and chemical formulae of reactants and products is called chemical reaction.
For example

2Mg + O₂ → 2MgO

The substances which participate in chemical reaction are called reactants and the new substances obtained after chemical reaction are called products.

→ Balanced Chemical Reaction Number of all the atoms remains equal in the reactants and products of a balanced chemical equation. The chemical reaction must always be balanced which is done by hit or trial method.

→ A complete chemical equation represents the reactants, products and their physical states symbolically.

→ The gaseous, liquid, aqueous and solid states of reactants and products are
represented by notations (g), (l), (aq) and (s), respectively.

→ Following observations may occur during a Chemical Reaction

(a) Change in state
(b) Change in colour
(c) Emission of a gas
(d) Change in temperature.

→ Types of Chemical Reactions-Generally chemical reactions are of following type –

(i) Combination reaction – In a combination reaction two or more substances combine to form a new single substance. For example –

CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat
C(s) + O₂(g) → CO₂(g)

(ii) Decomposition reaction – The reaction in which a single substance decomposes to give two or more substance is called decomposition reaction.
For example-

(iii) Displacement reaction – The reaction in which an element displaces another element from its compound is called displacement reaction.

Example –

(iv) Double displacement reaction-The reaction in which two different atoms or groups of atoms (ions) are exchanged, it is called double displacement reaction.
Example

(v) Oxidation and Reduction-In a reaction gain of oxygen or loss of hydrogen is called oxidation. The process of reduction is opposite to oxidation in which loss of oxygen or gain of hydrogen occurs.
Example –

(vi) Redox reaction – The chemical reactions in which oxidation and reduction reactions occurs simultaneously are called redox reactions. Example –

(vii) Precipitation reaction – The reactions in which a insoluble substance (precipitate) is formed are called precipitation reactions.
Example –

→ On the basis of heat, reactions are classified in two parts.
(a) Exothermic reaction – Reactions in which heat is given out along with the products are called exothermic reactions.
Example-CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g) + Energy

(b) Endothermic reaction-Reactions in which energy is absorbed are known as endothermic reactions.

Example –

→ Corrosion-When a metal comes in contact with acid, base or moisture then it will corrode. This process is called corrosion.

→ Rancidity-When fats and oils are left for a long time then taste and odour of these have changed due to oxidation. This is called rancidity.