Chemical Reactions And Equations Notes- Characteristics, Equations, Types

Chemical Reaction And The Equation Notes

A chemical reaction is when one chemical substance transforms into another. For example, a simple everyday process like the rusting of iron or the milk turning sour and changing into curd is a chemical reaction. Respiration and digestion is also chemical reaction.

When a chemical reaction occurs, a new substance is formed that is entirely different in its property from the original substance. This is because of the chemical change that takes place.

The rearrangement of atoms takes place in a chemical reaction. The substance that takes part in the chemical reaction is the reactant, and the new substance formed by the chemical reaction is the product.

In the example:

2Mg(s) O2(g) △→ 2MgO(s)

Mg and O2 are the reactants, and these are the substances that take part in the chemical reaction. MgO is a new product formed because of the chemical reaction, which is the product.

Chemical Reaction- Characteristics

Here are the chemical reaction characteristics.

• The evolution of gaseous matter happens when there is a chemical reaction between dilute sulphuric acid and zinc, giving off hydrogen gas.
• The color change happens in examples like a reaction between citric acid and potassium permanganate.
• State change occurs in the combustion of a candle.
• Temperature change occurs when quick lime water forms slaked lime.
• The precipitate is formed because of a chemical reaction between sulphuric acid and barium chloride solution.

Chemical Equation

When a chemical reaction is represented using formula and symbols, it is a chemical equation.

Example: A plus B → C plus D

A and B are the reactants, and C and D are the products.

The chemical equation is a method to represent the chemical reaction in an informative and concise manner. The chemical equation can be divided into a balanced chemical equation and an unbalanced one.

• A balanced chemical equation is where the number of atoms of each element is the same on both sides. This follows the law of conservation of mass, which states that it is impossible to create or destroy mass in any chemical reaction.
• An unbalanced chemical reaction is where the number of atoms in each reactant element is not equal to the number of atoms in each element present in the product. Then this is an unbalanced chemical reaction.

Making The Equation Informative

When you write the physical state of the substance in any chemical equation, it becomes informative.

• The gaseous state is represented by g
• The liquid state is represented by l
• The solid-state is represented by s
• The aqueous solution is represented by aq

Types Of Chemical Reactions

Let us now discuss the different types of chemical reactions

• A combination Reaction is a reaction where two or more two reactants combine to form a single product. When magnesium burns in oxygen, then it forms magnesium oxide.
• Decomposition Reaction is a reaction when one compound decomposes into two or more than two compounds, and it is the inverse of a combination reaction. When you heat calcium carbonate, then it decomposes into carbon dioxide and calcium oxide.
• Thermal decomposition is the decomposition of a substance when it is heated.
• Electrolytic decomposition is a reaction where the compound decomposes into a simple compound because of the electricity passing through it. It is also called electrolysis.
• Photolysis or Photo Decomposition Reaction is a reaction where the compound decomposes due to sunlight.
• A displacement reaction is a chemical reaction where a more reactive element will displace a less reactive element from a compound.
• A double Displacement Reaction is a reaction where the ions are exchanged between two reactants to form a new compound. 
• Precipitation Reaction is a reaction where the precipitate is formed by mixing the aqueous solution of the salts.
• Neutralization Reaction is a reaction where the acid and a base react to form water and salt because of ion exchange.
• Oxidation and Reduction Reactions:
• Oxidation is when oxygen or a non-metallic element is added, or hydrogen or a metallic element is removed
• Reduction is when hydrogen or a metallic element is added, or oxygen or a non-metallic element is removed
• An oxidizing agent is a substance that gives oxygen or removes hydrogen
• A reducing agent is a substance that gives hydrogen or removes oxygen
• Redox reaction is where oxidation and reduction occur simultaneously

• Exothermic and Endothermic Reactions:
• An exothermic reaction is a reaction where energy is produced. Most of the decomposition reactions occur because of an exothermic reaction. Respiration is an example of an exothermic reaction.
• An endothermic reaction is a chemical reaction where heat energy gets absorbed. Like when calcium carbonate is decomposed.

Corrosion And Rancidity

The oxidation reaction is the reason for corrosion and rancidity. Corrosion is the slow metal conversion into an undesirable compound when it reacts with water, oxygen gases, and acids.

Rancidity is when the odor and taste of the food material that contains oil and fat change when it is left exposed for a very long time in the air. It happens because of fat and oil oxidation. 

Conclusion

A chemical reaction is when a chemical substance is transformed into a new chemical substance which occurs by breaking bonds between the atoms. When this reaction is expressed in the form of an equation, then this is the chemical equation.

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