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.
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.
(iii) Displacement reaction – The reaction in which an element displaces another element from its compound is called displacement reaction.
(iv) Double displacement reaction-The reaction in which two different atoms or groups of atoms (ions) are exchanged, it is called double displacement reaction.
(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.
(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.
→ 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.
→ 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.