This chapter explains how substances undergo chemical changes to form new substances through chemical reactions. It helps students identify chemical reactions by observing changes such as colour change, gas evolution, temperature change, or formation of a precipitate. The chapter introduces the correct way of representing reactions using word equations and balanced chemical equations, highlighting the importance of the law of conservation of mass. It also discusses different types of chemical reactions and their effects in everyday life, including corrosion and rancidity.
Key Points
A chemical reaction involves the conversion of reactants into products.
Chemical reactions are identified by observable changes like colour change, gas evolution, temperature change, or precipitate formation.
A word equation represents a reaction using words.
A chemical equation uses symbols and formulae to represent reactions.
A skeletal equation is an unbalanced chemical equation.
Balanced chemical equations follow the law of conservation of mass.
Physical states of substances are shown using (s), (l), (g), and (aq).
Combination reactions form a single product from two or more reactants.
Decomposition reactions break a compound into simpler substances.
Displacement reactions occur when a more reactive element replaces a less reactive one.
Double displacement reactions involve exchange of ions between compounds.
Oxidation is gain of oxygen or loss of hydrogen.
Reduction is loss of oxygen or gain of hydrogen.
Oxidation and reduction occur together and are called redox reactions.
Corrosion is the slow destruction of metals by reaction with air, moisture, or chemicals.
Rancidity is the oxidation of fats and oils causing spoilage of food.
👉 👉Chemical reactions explain the changes happening all around us, from rusting of iron to digestion of food. Understanding chemical equations and reaction types helps us control reactions, prevent damage like corrosion, preserve food, and apply chemistry safely and responsibly in daily life and industry.