🧪 Chemical Reactions & Equations – Quick Revision
🔹 1. 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 (heat/light produced)
★Formation of gas
★Formation of precipitate (solid)
🔹 2. Chemical Equation
~Representation of a chemical reaction using symbols and formulas.
Example:
Word equation:
★Magnesium + Oxygen → Magnesium oxide
Chemical equation:
Mg + O₂ → MgO
🔹 3. Balanced Chemical Equation
~An equation where number of atoms of each element is same on both sides.
Example:
Unbalanced:
★Fe + H₂O → Fe₃O₄ + H₂
Balanced:
3Fe + 4H₂O → Fe₃O₄ + 4H₂
🔹 4. Types of Chemical Reactions
(i) Combination Reaction
Two or more substances combine to form one product.
👉
A + B → AB
Example:
CaO + H₂O → Ca(OH)₂
(ii) Decomposition Reaction
One substance breaks into simpler substances.
👉
AB → A + B
Types:
Thermal (heat)
🔹 1. 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 (heat/light produced)
★Formation of gas
★Formation of precipitate (solid)
🔹 2. Chemical Equation
~Representation of a chemical reaction using symbols and formulas.
Example:
Word equation:
★Magnesium + Oxygen → Magnesium oxide
Chemical equation:
Mg + O₂ → MgO
🔹 3. Balanced Chemical Equation
~An equation where number of atoms of each element is same on both sides.
Example:
Unbalanced:
★Fe + H₂O → Fe₃O₄ + H₂
Balanced:
3Fe + 4H₂O → Fe₃O₄ + 4H₂
🔹 4. Types of Chemical Reactions
(i) Combination Reaction
Two or more substances combine to form one product.
👉
A + B → AB
Example:
CaO + H₂O → Ca(OH)₂
(ii) Decomposition Reaction
One substance breaks into simpler substances.
👉
AB → A + B
Types:
Thermal (heat)
