Part 1: Introduction, Chemical Reaction and Chemical Equations
Introduction
In our daily life, many changes take place around us. Some changes are physical and some are chemical.
When a chemical change occurs and new substances are formed, it is called a chemical reaction.
Examples of chemical reactions in daily life :
- Burning of candle
- Rusting of iron
- Cooking of food
- Digestion of food
WHAT IS A CHEMICAL REACTION?
A chemical reaction is a process in which one or more substances react together to form new substances with different properties.
The substances which take part in a chemical reaction are called reactants.
The new substances formed after the reaction are called products.
Example:
Magnesium + Oxygen → Magnesium Oxide
Here,
Reactants: Magnesium and Oxygen
Product: Magnesium Oxide
CHARACTERISTICS OF A CHEMICAL REACTION
A chemical reaction can be identified by the following changes:
- Change in colour
Example: Iron changes its colour when it rusts. - Change in temperature
Example: Heat is produced when a candle burns. - Formation of gas
Example: Gas is released when zinc reacts with acid. - Formation of precipitate
Example: A white precipitate is formed when two solutions react. - Change in state
Example: Water changes into steam on heating.
CHEMICAL EQUATION
A chemical equation is a way to represent a chemical reaction using symbols and formulas.
Example:
Magnesium + Oxygen → Magnesium Oxide
WORD EQUATION
A chemical equation written using words instead of symbols is called a word equation.
Example:
Magnesium + Oxygen → Magnesium Oxide
SYMBOLIC (FORMULA) EQUATION
When chemical symbols and formulas are used, it is called a symbolic equation.
Example:
2Mg + O₂ → 2MgO
BALANCED AND UNBALANCED CHEMICAL EQUATION
Unbalanced Chemical Equation:
An equation in which the number of atoms of each element is not equal on both sides is called an unbalanced equation.
Example:
Mg + O₂ → MgO
Balanced Chemical Equation:
An equation in which the number of atoms of each element is equal on both sides is called a balanced equation.
Example:
2Mg + O₂ → 2MgO
TYPES OF CHEMICAL REACTIONS (Introduction)
- Combination Reaction
- Decomposition Reaction
- Displacement Reaction
- Double Displacement Reaction
- Oxidation and Reduction Reaction
(Detailed explanation will be given separately.)
IMPORTANT KEYWORDS
- Chemical Reaction
- Reactants
- Products
- Chemical Equation
- Balanced Equation
- Unbalanced Equation