Definition of Decomposition
Decomposition can be defined as a process of breaking down or simplifying any physical or chemical entity. Chemical decomposition is sometimes also referred to as chemical breakdown. Chemical decomposition is the effect of simplifying a complex chemical entity into a single chemical entity into two or more fragments. Generally, it is the exact opposite of chemical synthesis. The breakdown of hydrogen peroxide to water and oxygen and the breakdown of water to hydrogen and oxygen are examples of chemical decompositions. In this article we are going to discuss the types of decomposition with examples in detail.
Decomposition Types
The decomposition is classified broadly into two types because changes can be of two types. There are two types of decomposition or we can say changes, which are given below.
Physical decomposition or changes
Chemical decomposition or changes
Physical changes are generally reversible changes but they can be also irreversible and only the physical properties are changed in such changes. In a physical change, a substance undergoes a change of its physical properties. Some common examples of physical changes are melting an ice cube, boiling of water, breaking of a glass, freezing water etc.
Chemical changes are irreversible changes in which new products are formed. The product is different from the reactants and has entirely different properties. Chemical changes that occur are also considered chemical reactions. A short way of writing a chemical reaction or the chemical changes are through chemical equations. Chemical equations are a symbolic representation of a chemical reaction. When one writes chemical reaction symbols of elements, arrows, etc are used.
Decomposition reaction - In this type of chemical reaction, one reactant breaks to form several products. It is just opposite to the combination reaction.
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Decomposition Meaning of Chemistry
Decomposition in chemistry means breaking a single reactant to form more stable products compared to the reactant. Decomposition is an essential process of chemistry as it results in the formation of new products. In our daily life, we see examples of chemical decomposition. For example when we open any soda bottle carbonic acid chemicals decompose into water and carbon dioxide, which creates the fizz.
Types of Decomposition Reactions
A decomposition reaction is classified into three types-
Thermal decomposition
Electrolytic decomposition
Photo decomposition
Now know about each type of decomposition reaction in detail.
Thermal Decomposition
It is a type of decomposition in which a single reactant is broken down into more than one product with the help of heat. Thermal energy or heat energy is used to break the reactants. This is an endothermic reaction as heat is used to break the bonds of the reactants. Calcium carbonate is decomposed from heat to form calcium oxide and carbon dioxide.
CaCO3→CaO + CO2
Photo Decomposition
It is a type of decomposition reaction in which light or photons are used to break the reactants to form several products. Light energy is used to break the bonds in the reactant. This reaction is also known as photolysis.
Silver chloride decomposes in the presence of sunlight to form silver metal and chlorine gas.
AgCl→Ag + Cl2
Electrolytic Decomposition
A single reactant is broken down into several products using electricity. This type of decomposition reaction is electrolytic decomposition. The decomposition of water is a good example of electrolytic decomposition.
H2O→ H2 + O2
Decomposition Reaction Examples
There are several examples of decomposition. Some of them are given below-
Carbonic acid in soft drinks decomposes to give carbon dioxide gas.
Hydrogen gas and oxygen gas are released from the decomposition of water.
Digestion of food is a decomposition reaction. Through this reaction, nutrients are released from the food eaten.
Iron sulphate which is of green colour is decomposed to form a brown-coloured ferric oxide and gases like sulphur dioxide and sulphur trioxide gases are released.
Lead nitrate on thermal decomposition gives lead monoxide which is yellow. With this brown gas nitrogen dioxide and oxygen gas are released.
Hence, decomposition is a process that results in a change that can be reversible or irreversible. It is an important process because many of the time decomposition is a need for the production or manufacture of any new product. In this article, we learnt about the type of decomposition and its examples as well.
FAQs on Decomposition
1. What is a decomposition reaction as per the CBSE Class 10 syllabus?
A decomposition reaction is a type of chemical reaction in which a single compound breaks down into two or more simpler substances when energy is supplied. It is the opposite of a combination reaction. The general form of this reaction is AB → A + B, where AB is the reactant and A and B are the simpler products.
2. What are the main types of decomposition reactions, and what form of energy does each use?
Based on the type of energy used to break down the reactant, decomposition reactions are classified into three main types:
- Thermal Decomposition: This reaction uses heat energy to break down a compound. For example, heating calcium carbonate to get calcium oxide and carbon dioxide.
- Electrolytic Decomposition (Electrolysis): This reaction uses electrical energy to decompose a compound. For example, passing electricity through water to produce hydrogen and oxygen gas.
- Photolytic Decomposition (Photolysis): This reaction uses light energy to break down a compound. For example, exposing silver chloride to sunlight causes it to decompose into silver and chlorine.
3. Why are most decomposition reactions considered endothermic?
Decomposition reactions are generally endothermic because they involve breaking existing chemical bonds within the reactant molecule. Breaking chemical bonds always requires an input of energy from the surroundings. This energy is absorbed in the form of heat, light, or electricity, causing the reaction to be endothermic.
4. How is a decomposition reaction fundamentally different from a combination reaction?
The fundamental difference lies in the number of reactants and products. In a decomposition reaction, one single reactant breaks down to form multiple simpler products (1 → 2+). In contrast, a combination reaction involves two or more reactants combining to form a single, more complex product (2+ → 1). For example, the decomposition of water (2H₂O → 2H₂ + O₂) is the exact opposite of the combination reaction that forms it (2H₂ + O₂ → 2H₂O).
5. A student heats white crystals of lead nitrate in a test tube. What key observations would they make? Identify the reaction type.
When white, crystalline lead nitrate (Pb(NO₃)₂) is heated, the following observations are made:
- The white solid decomposes.
- A brown gas is evolved, which is nitrogen dioxide (NO₂).
- A yellow solid residue of lead(II) oxide (PbO) is left behind in the test tube.
This is a classic example of a thermal decomposition reaction. The balanced chemical equation is: 2Pb(NO₃)₂(s) → 2PbO(s) + 4NO₂(g) + O₂(g).
6. What are some important industrial and daily-life applications of decomposition reactions?
Decomposition reactions have several crucial applications:
- Metal Extraction: Electrolytic decomposition is used to extract highly reactive metals like sodium and aluminium from their molten ores.
- Cement Manufacturing: The thermal decomposition of limestone (calcium carbonate) to produce quicklime (calcium oxide) is a vital step in making cement.
- Photography: The photolytic decomposition of silver bromide (AgBr) on photographic film is the principle behind black-and-white photography.
- Daily Life: When you open a soda bottle, the carbonic acid in it decomposes into water and carbon dioxide, creating the fizz.
7. Is the digestion of food in our body an example of a decomposition reaction?
Yes, digestion is a complex form of decomposition. It is a series of biochemical decomposition reactions. In this process, large, complex, and insoluble food molecules like carbohydrates and proteins are broken down by biological catalysts called enzymes into smaller, simpler, and soluble molecules like glucose and amino acids. These simpler molecules can then be absorbed by the body. It differs from simple thermal or photolytic decomposition as it is driven by enzymes at body temperature.
