A chemical reaction is when substances (called reactants) interact to form new substances (called products) with different properties. During a chemical reaction, the molecules of the reactants rearrange to create new molecules, often resulting in changes like color, temperature, or the formation of gas or a solid.
Primarily there are 5 types of chemical reactions
- Combination Reactions
- Decomposition Reactions
- Displacement Reactions
- Double Displacement Reactions
- Precipitation Reactions
Combination Reactions
A combination reaction occurs when two or more reactants combine to form a single product. This type of reaction is also known as a synthesis reaction. For example:
A+B→AB
Example: When hydrogen (H₂) and oxygen (O₂) combine to form water (H₂O): 2H2+O2→2H2O
Decomposition Reactions
A decomposition reaction occurs when a single compound breaks down into two or more simpler substances. This reaction is the opposite of a combination reaction.
AB→A+B
Example: The decomposition of calcium carbonate (CaCO₃) when heated produces calcium oxide (CaO) and carbon dioxide (CO₂):
CaCO3→CaO+CO2
Displacement Reactions
In a displacement reaction, one element displaces another from a compound.
A+BC→AC+B
Example: When zinc (Zn) reacts with hydrochloric acid (HCl), zinc chloride (ZnCl₂) and hydrogen gas (H₂) are formed:
Zn+2HCl→ZnCl2+H2
Double Displacement Reactions
Instead of one element, in double displacement reactions, two compounds are exchanged and form two new compounds.
AB+CD→AD+CB
Example: When silver nitrate (AgNO₃) is added to sodium chloride (NaCl), silver chloride (AgCl) and sodium nitrate (NaNO₃) are formed:
AgNO3+NaCl→AgCl+NaNO3
Precipitation Reactions
Precipitation reactions are a type of reaction that involves the formation of insoluble products also called precipitate.
The reactants in this reaction are soluble but the product is insoluble and separates out as a solid.
AB+CD→AD+BD(S)
Example: When aqueous solution of Sodium Chromate (Na2CrO4) is added to aqueous solution of Silver Nitrate (AgNO3), aqueous Sodium Nitrate (NaCO3) is formed along with Silver Chloride (AgCl) as solid precipitate.
Na2CrO4(aq) + 2AgNO3(aq) → Ag2CrO4(s) + 2NaNO3(aq)
Apart from the above-mentioned chemical reactions, there are other chemical reactions as followed:
Combustion Reaction
Combustion reactions involve the reaction of a substance with oxygen, producing heat and light (energy). These reactions are commonly associated with the burning of fuels.
Fuel+O2→CO2+H2O+Energy
Example: The combustion of methane (CH₄) in the presence of oxygen produces carbon dioxide, water, and energy:
CH4+2O2→CO2+2H2O
Neutralisation Reactions
A neutralisation reaction occurs when an acid and a base react to form salt and water. This type of reaction is a specific case of a double displacement reaction.
Acid+Base→Salt+Water
Example: When hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), sodium chloride (NaCl) and water are formed:
HCl+NaOH→NaCl+H2O
Redox Reactions
A Redox (reduction-oxidation) reaction involves the transfer of electrons between two substances. In these reactions, one substance is oxidised (loses electrons), and the other is reduced (gains electrons).
Example: In the reaction between iron (Fe) and copper(II) sulphate (CuSO₄), iron is oxidised to iron(II) sulphate (FeSO₄), and copper is reduced:
Fe+CuSO4→FeSO4+Cu
|
Type of Chemical Reaction |
Description |
General Reaction |
|
Combination Reaction |
Two or more compounds/elements react to form one compound, |
A + B → AB |
|
Decomposition Reaction |
A complex compound breaks down to simple compounds/elements. |
AB → A + B |
|
Displacement Reaction |
One element displaces another in the reaction. |
AB + C → AC + B |
|
Double Displacement Reaction |
Two compounds are exchanged and form two new compounds. |
AB + CD → AC + BD |
|
Precipitation Reaction |
Two soluble salt solutions are combined, a precipitate—an insoluble solid—is formed. |
A + soluble salt B → Precipitate + soluble salt C |
|
Combustion Reaction |
Water and carbon dioxide are formed when a chemical and oxygen interact. Since these processes release heat, they are exothermic. |
A + O2 → H2O + CO2 |
|
Neutralisation Reaction |
Acid and base reacts to form salt and water. |
Acid + Base → Salt + Water |
|
Redox Reaction |
One compound/element is oxidised and other is reduced in the reaction. |
A + B → A(Oxidised) + B(Reduced) |
Conclusion
Understanding the different types of chemical reactions is fundamental to grasping the basic principles of chemistry. These reactions not only explain how substances interact but also provide insight into the transformative processes that shape the natural and industrial worlds
At Centre Point School, we believe in nurturing curiosity and a love for learning in our students. Our method of teaching science is to encourage curiosity and practical application. We hope to equip kids for a lifetime of exploration and growth by encouraging their engagement with scientific concepts via hands-on activities and group learning. We take pride in providing a learning environment where students can explore their scientific interests and acquire the skills necessary to flourish in an ever changing world.
