- Thermal decomposition involves heating a compound to break it into simpler substances, e.g.,
2Pb(NO₃)₂ ⟶ 2PbO + 4NO₂ + O₂ (brown fumes of NO₂ observed). - Electrolytic decomposition uses electricity to decompose compounds, e.g.,
2H₂O ⟶ 2H₂ + O₂ (Electrolysis of water gives hydrogen and oxygen gases). - Photodecomposition occurs when light energy breaks down a compound, e.g.,
2AgCl ⟶ 2Ag + Cl₂ (white silver chloride turns grey in sunlight). - Thermal decomposition of calcium carbonate produces lime (CaO) and CO₂ gas, which turns lime water milky.
- Decomposition reactions are usually endothermic and require heat, light, or electricity to occur (e.g., the decomposition of ferrous sulphate, calcium carbonate, or sugar).
Topics
Chemical Substances-Nature and Behaviour
Chemical Reactions and Equations
- Chemical Reaction
- Characteristics of Chemical Reactions
- Chemical Equations
- Balanced and Unbalanced Chemical Equations
- Balancing Chemical Equation
- Types of Chemical Reactions > Combination Reaction
- Types of Chemical Reactions > Decomposition Reaction
- Types of Chemical Reactions > Single Displacement Reaction
- Types of Chemical Reactions > Double Displacement Reaction
- Types of Chemical Reactions > Reversible and Irreversible Reactions
- Types of Chemical Reactions > Oxidation and Reduction Reactions
- Corrosion of Metals
- Rancidity
World of Living
Acids, Bases and Salts
- Introduction to Acids, Bases and Indicators
- Indicators for Testing Acids and Bases
- Acids
- Properties of Acids
- Common Properties of Acids
- Uses of Acids
- Bases
- Properties of Bases
- Uses of Bases
- Chemical Properties of Acids and Bases
- Common Properties of Acids and Bases
- Strength of Acid and Base Solutions : pH Scale
- Universal Indicator
- Importance of pH in Everyday Life
- Salts
- Salts > Family of Salts
- Salts > pH of Salts
- Common Salt
- Sodium hydroxide
- Washing Soda
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- Plaster of Paris
- Water of Crystallisation: Hydrated Salts
Natural Phenomena
Metals and Non-metals
Carbon and its Compounds
Effects of Current
Life Processes
Natural Resources
Control and Coordination
How do Organisms Reproduce?
- DNA Copying and Variation
- The Importance of Variation
- Reproduction
- Modes of Reproduction
- Asexual Reproduction
- Asexual Reproduction in Unicellular Organisms > Binary Fission
- Binary Fission > Simple Binary Fission
- Binary Fission > Longitudinal Binary Fission
- Binary Fission > Transverse Binary Fission
- Asexual Reproduction in Unicellular Organisms > Multiple Fission
- Asexual Reproduction in Multicellular Organisms > Fragmentation
- Asexual Reproduction in Multicellular Organisms > Regeneration
- Asexual Reproduction in Unicellular Organisms > Budding
- Asexual Reproduction in Multicellular Organisms > Budding
- Asexual Reproduction in Multicellular Organisms > Spore Formation
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- Tissue Culture
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- Pollination
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- Formation of Seed and Fruit
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- Major Events of Menstrual Cycle
- Menarche and Menopause
- Birth Control
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- Concept of Reproductive Health
Heredity
- Heredity
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- Accumulation of Variation During Reproduction
- Gregor Johann Mendel – Father of Genetics
- Monohybrid Cross
- Dihybrid Cross
- Characteristics (or Traits) Transmitted to Progeny
- Inheritance of Blood Groups
- Sex Determination in Humans
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Light – Reflection and Refraction
- Nature of Light
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- Reflection of Light from Plane Surfaces: Plane Mirror
- Law of Reflection of Light
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- The Position of Image Formed in a Plane Mirror
- Uses of Plane Mirrors
- Spherical Mirrors
- Image Formation by Spherical Mirrors
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- Formation of Different Types of Images by a Concave Mirror
- Representation of Images Formed by Spherical Mirrors Using Ray Diagrams
- Sign Convention for Reflection by Spherical Mirrors
- Mirror Formula and Magnification
- Rules for Obtaining Images Formed by Convex Mirrors
- Formation of Image by a Convex Mirror
- Refraction of Light
- Effects of Refraction of Light
- Laws of Refraction of Light
- Refraction through a Rectangular Glass Slab
- The Refractive Index
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- Rules for Obtaining Images Formed by Convex Lenses
- Formation of Different Types of Images by a Convex Lens
- Image Formation by Lenses
- Image Formation in Lenses Using Ray Diagrams
- Sign Convention for Reflection by Spherical Mirrors
- Lens Formula and Magnification
- Lens Formula and Magnification Formulae for a Concave Lens
- Power of a Lens
The Human Eye and the Colourful World
- Human Eye
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- Advantages of Having Two Eyes for Vision
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- Defects of Vision and Their Corrections > Hypermetropia
- Defects of Vision and Their Corrections > Presbyopia
- Glass Prism
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- The Rainbow
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- Scattering of Light
Electricity
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Magnetic Effects of Electric Current
- Introduction to Magnets and Their Properties
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- Right-hand Thumb Rule
- Magnetic Field due to a Current through a Circular Loop
- Magnetic Field due to a Current in a Solenoid
- Electromagnet
- Magnetism in Human Beings
- Force on a Current-Carrying Conductor in a Magnetic Field
- Domestic Electric Circuits
Our Environment
CBSE: Class 10
Maharashtra State Board: Class 10
Maharashtra State Board: Class 10
Definition: Decomposition Reaction
A single reactant breaks down to give simpler products. This is a decomposition reaction.
OR
The chemical reaction in which two or more products are formed from a single reactant is a decomposition reaction.
CBSE: Class 10
Definition: Thermal Decomposition
When a decomposition reaction is carried out by heating, it is called thermal decomposition.
CBSE: Class 10
Maharashtra State Board: Class 10
Maharashtra State Board: Class 10
Key Points: Decomposition Reaction
Maharashtra State Board: Class 10
Experiment
1. Aim: To observe and understand decomposition reactions, where a single reactant breaks down into two or more simpler substances.
2. Requirements
- Apparatus: evaporating dish, test tubes, bent tube, rubber cork, Bunsen burner.
- Chemicals: sugar, calcium carbonate (CaCO₃), sulphuric acid, freshly prepared lime water.
4. Procedure
Experiment 1: Decomposition of Sugar
- Take some sugar in an evaporating dish.
- Heat it using a Bunsen burner and observe the changes.
- A black residue (carbon) forms, and water (H₂O) vapour is released.
\[\mathrm{C}_{12}\mathrm{H}_{22}\mathrm{O}_{11}\xrightarrow{\mathrm{Heat}}12C+11H_2O\]
Experiment 2: Decomposition of Calcium Carbonate
- Take some calcium carbonate (CaCO₃) in a test tube.
- Fit a bent tube into the test tube using a rubber cork.
- Insert the other end of the bent tube into another test tube containing freshly prepared lime water.
- Heat the calcium carbonate strongly. The lime water turns milky, indicating the presence of carbon dioxide (CO₂) gas.
\[\mathrm{CaCO}_3(s)\xrightarrow{\Delta}\mathrm{CaO}(s)+\mathrm{CO}_2\uparrow\]
Decomposition of calcium carbonate
Experiment 3: Electrolysis of Water
- Pass electric current through acidulated water.
- Observe the formation of hydrogen (H₂) and oxygen (O₂) gases.
\[2H_2O(l)\xrightarrow{\text{Electrical Energy}}2H_2\uparrow+O_2\uparrow\]
5. Conclusion: A decomposition reaction occurs when a single reactant breaks down into two or more simpler substances. These reactions can be thermal (heat-driven), electrolytic (electricity-driven), or biological (natural degradation by microorganisms). Decomposition reactions are crucial in nature, industry, and energy production, such as in the formation of biogas from organic waste.
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