Class 10 Science – Chapter 1: Chemical Reactions and Equations

What is a Chemical Reaction?

A process in which one or more substances (reactants) change into new substances (products) with different properties.

Signs of a Chemical Reaction

Change in colour, change in temperature, evolution of gas, formation of precipitate, change in state.

Chemical Equation

A representation of a chemical reaction using symbols and formulae.

Word Equation

A representation of a chemical reaction using the names of the reactants and products.

Balanced Chemical Equation

An equation that has the same number of atoms of each element on both sides.

Why is balancing necessary in chemical equations?

Because of the Law of Conservation of Mass, which states that matter can neither be created nor destroyed during a chemical reaction.

Combination Reaction

A reaction where two or more substances combine to form one product.

Decomposition Reaction

A reaction in which one compound breaks down into two or more simpler substances.

Displacement Reaction

A reaction where a more reactive element displaces a less reactive element.

Double Displacement Reaction

A reaction involving the exchange of ions between two compounds.

Neutralization Reaction

A reaction between an acid and a base to produce a salt and water.

Oxidation

The gain of oxygen or loss of hydrogen during a reaction.

Reduction

The loss of oxygen or gain of hydrogen during a reaction.

Corrosion

The slow destruction of metals due to reaction with air and moisture.

Rancidity

The oxidation of oils and fats, causing bad smell and taste.

Reactants

Substances that take part in a chemical reaction.

Products

New substances formed as a result of a chemical reaction.

Precipitate

An insoluble solid that forms during a chemical reaction.

Catalyst

A substance that increases the rate of a reaction without being consumed in the process.