Grade 9
  1. Matter and its nature  1.1. Introduction to matter  1.2. Physical and chemical properties of matter  1.3. States of matter  1.3.1. Solid state  1.3.2. Fluid state  1.3.3. Gaseous state  1.3.4. Plasma and Bose–Einstein condensate  1.4. Changes in the states of matter  1.4.1. Melting and freezing  1.4.2. Evaporation and Condensation  1.4.3. Sublimation and deposition  1.5. Classification of matter  1.6. Elements, Compounds, and Mixtures  1.7. Pure substances and impurities  1.8. Separation Techniques  1.8.1. Filtration  1.8.2. Distillation  1.8.3. Crystallization  1.8.4. Chromatography  1.8.5. Centrifugation  1.8.6. Sublimation  1.8.7. Decantation and sedimentation
  2. Atomic Structure  2.1. Discovery of atoms  2.2. Dalton's atomic theory  2.3. Structure of the atom  2.4. Subatomic particles  2.5. Atomic number and mass number  2.6. Isotopes and Isobars  2.7. Electronic configuration  2.8. Bohr's atomic model  2.9. Modern Atomic Model (Quantum Mechanical Model - Introduction)  2.10. Valency and chemical bonding
  3. C hemical reactions and equations  3.1. Introduction to Chemical Reactions  3.2. Chemical Equation Formulation  3.3. Balancing Chemical Equations  3.4. Types of Chemical Reactions  3.4.1. Combination Reactions  3.4.2. Decomposition reactions  3.4.3. Displacement reactions  3.4.4. Double displacement reactions  3.4.5. Redox reactions  3.4.6. Endothermic and Exothermic Reactions  3.5. Effects of chemical reactions  3.6. Energy Changes in Chemical Reactions  3.7. Catalysts and their role in reactions
  4. Periodic table and periodicity  4.1. History of Periodic Classification  4.2. Mendeleev's periodic table  4.3. Modern Periodic Table  4.4. Periods and groups in the periodic table and periodicity  4.5. Trends in the Periodic Table  4.5.1. Atomic size  4.5.2. Ionization Energy  4.5.3. Electron affinity  4.5.4. Electronegativity  4.5.5. Metallic and Non-Metallic Properties  4.6. Noble gases and their properties
  5. Chemical bond  5.1. Introduction to Chemical Bonding  5.2. Types of chemical bonds  5.2.1. Ionic bond  5.2.2. Covalent bond  5.2.3. Metallic bond  5.2.4. Hydrogen bonding  5.2.5. Van der Waals force  5.3. Properties of Ionic and Covalent Compounds  5.4. Molecular Structure and Geometry (VSEPR Theory - Basics)
  6. Acids, Bases and Salts  6.1. Introduction to Acids and Bases  6.2. Properties of Acids  6.3. Properties of bases  6.4. pH scale and its importance  6.5. Indicators and their uses  6.6. Neutralization reactions  6.7. Strength of Acids and Bases (Strong vs. Weak)  6.8. Preparation of salts  6.9. Uses of acids, bases and salts in daily life
  7. Metals and Nonmetals  7.1. Physical Properties of Metals  7.2. Physical Properties of Nonmetals  7.3. Chemical properties of metals  7.4. Chemical Properties of Nonmetals  7.5. Reactivity Series of Metals  7.6. Extraction of metals  7.7. Corrosion and its prevention  7.8. uses of metals and nonmetals
  8. Carbon and its compounds  8.1. Introduction to Carbon  8.2. Allotropes of carbon (diamond, graphite, fullerene)  8.3. Hydrocarbons  8.3.1. Hydrocarbons  8.3.2. Alkene  8.3.3. Alkynes  8.4. Functional groups in organic chemistry  8.5. Isomerism in organic compounds  8.6. Alcohols and Carboxylic Acids  8.7. Soaps and detergents  8.8. Polymers (Introduction to Natural and Synthetic Polymers)
  9. Solutions and Mixtures  9.1. Types of mixtures  9.2. Homogeneous and Heterogeneous Mixtures  9.3. Concentration of solutions  9.4. Solubility and factors affecting solubility  9.5. Suspensions and Colloids  9.6. Saturated, unsaturated and supersaturated solutions
  10. Air and atmosphere  10.1. Composition of air  10.2. Role of gases in the atmosphere  10.4. Acid rain and its effects  10.5. Greenhouse effect and global warming  10.6. Ozone layer and its depletion  10.7. Air pollution control measures
  11. Water and its importance  11.1. Composition and properties of water  11.2. Hardness of water (temporary and permanent hardness)  11.3. Causes of water pollution  11.4. Effects of Water Pollution  11.5. Water purification methods (filtration, boiling, chlorination)
  12. Industrial Chemistry  12.1. Introduction to Industrial Chemistry  12.2. Important industrial chemicals (sulfuric acid, ammonia, sodium hydroxide)  12.3. Chemical processes in industry  12.4. Uses of Industrial Chemistry in Daily Life  12.5. Environmental impact of industrial chemical processes

Grade 9 → C hemical reactions and equations → Types of Chemical Reactions ↓


Decomposition reactions


Chemistry involves understanding how substances interact with each other and undergo changes to form new substances. One of these processes is the decomposition reaction, which is a fascinating type of chemical reaction. Let's learn in detail what decomposition reactions are and how they occur.

What is a decomposition reaction?

A decomposition reaction is a type of chemical reaction in which a single compound breaks down into two or more simpler substances. These reactions are the opposite of combination reactions and require energy in the form of heat, light, or electricity.

General formula of decomposition reactions

The general equation for the decomposition reaction can be written as:

AB → A + B

In this equation, AB is a compound that disintegrates into A and B, which are simpler substances.

Types of decomposition reactions

Decomposition reactions can occur in different ways depending on the type of energy involved in breaking down the compounds. The main types are:

1. Thermal decomposition

Thermal decomposition occurs with the application of heat. When a compound is heated, it breaks down into simpler substances. These reactions are common in metal carbonates and nitrates.

Heat

Example:

CaCO₃ (s) → CaO (s) + CO₂ (g)

Here, calcium carbonate (CaCO₃) decomposes into calcium oxide (CaO) and carbon dioxide gas (CO₂) when heated.

2. Electrolytic decomposition

In this type of reaction, electric current is used to decompose the compound. It is widely used in the electrolytic extraction of metals.

Electricity

Example:

2H₂O (l) → 2H₂ (g) + O₂ (g)

In this example, when electric current is passed through water (H₂O), it disintegrates into hydrogen gas (H₂) and oxygen gas (O₂).

3. Photodecomposition (or photolysis)

Photodecomposition reactions occur when light energy breaks chemical bonds in a compound. These are also called photolysis reactions.

lights

Example:

2AgCl (s) → 2Ag (s) + Cl₂ (g)

In the above example, silver chloride (AgCl) decomposes into silver (Ag) and chlorine gas (Cl₂) in the presence of light.

Characteristics of decomposition reactions

Endothermic process

Decomposition reactions usually require energy in the form of heat, light or electricity. This energy is necessary to break the chemical bonds in the compound.

Manufacture of multiple products

Decomposition reactions yield two or more products. The nature and state (solid, liquid, gas) of these products depend on the original compound and the conditions under which the reaction occurs.

Real life applications of decomposition reactions

Decomposition reactions are prevalent in a variety of industrial processes and natural phenomena. Here are some examples:

In the industry

Decomposition reactions are important in manufacturing industries such as the production of cement, where limestone (CaCO₃) is decomposed into lime (CaO) and carbon dioxide (CO₂).

In fireworks

Decomposition reactions are used to create bright colors in fireworks displays. The compounds in a firework shell decompose when burned, releasing colored gases and energy.

In daily life

Baking involves decomposition reactions. Baking soda (NaHCO₃) decomposes when heated in the oven, producing carbon dioxide (CO₂) that helps the dough rise.

2NaHCO₃ (s) → Na₂CO₃ (s) + H₂O (l) + CO₂ (g)

Factors affecting decomposition reactions

Several factors determine the rate and occurrence of decomposition reactions:

Temperature

As the temperature increases, the energy available to break the bonds increases, speeding up the decomposition reaction.

Catalyst

Catalysts can lower the activation energy needed for the reaction, thereby speeding up the decomposition. Although they are not consumed in the process, they provide an alternative route for the reaction to take place.

Concentration

In cases where solutions are involved, higher concentrations of the reactant usually increase the rate of decomposition.

Conclusion

Decomposition reactions are an essential type of chemical reaction in which complex compounds are broken down into simpler compounds. They require energy and are found in a variety of applications from industry to daily life. Understanding decomposition reactions provides insight into chemical processes and helps in harnessing them for practical uses.


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Combination Reactions
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Displacement reactions

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Decomposition reactions

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