Chemical reactions and equations class 10th chapter NCERT

 Definitions of chemical reactions chemical equations and types of chemical reactions

Chemical Reactions:

A chemical reaction is a process in which one or more substances are transformed into one or more different substances. It involves the breaking and formation of chemical bonds, resulting in a rearrangement of atoms to form new chemical substances with different properties.

Chemical Equations:

A chemical equation is a symbolic representation of a chemical reaction that shows the reactants, products, and their respective stoichiometric coefficients. It is a concise way to represent a chemical reaction using chemical formulas and symbols.

Types of Chemical Reactions:

Combination Reaction: A combination reaction is a type of reaction in which two or more reactants combine to form a single product.

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Decomposition Reaction: A decomposition reaction is a type of reaction in which a single reactant breaks down into two or more products.

 

Single Displacement Reaction: A single displacement reaction is a type of reaction in which an element or ion in a compound is displaced by another element or ion.

 

Double Displacement Reaction: A double displacement reaction is a type of reaction in which two ionic compounds exchange ions to form two new compounds.

 

Acid-Base Reaction: An acid-base reaction is a type of reaction in which an acid reacts with a base to form a salt and water

Definition of oxidation reduction and redox reaction

Oxidation:

Oxidation is a chemical process that involves the loss of electrons, an increase in oxidation state, or a loss of hydrogen atoms from a molecule. In simple terms, it is a reaction in which a substance loses one or more electrons.

Reduction:

Reduction is a chemical process that involves the gain of electrons, a decrease in oxidation state, or a gain of hydrogen atoms in a molecule. In simple terms, it is a reaction in which a substance gains one or more electrons.

Redox Reaction:

A redox reaction, short for reduction-oxidation reaction, is a type of chemical reaction in which there is a transfer of electrons between the reactants. It involves both oxidation and reduction reactions occurring simultaneously. In a redox reaction, one reactant loses electrons (undergoes oxidation) and another reactant gains electrons (undergoes reduction).

The substance that loses electrons is called the reducing agent, and the substance that gains electrons is called the oxidizing agent. Redox reactions are important in many biological processes, such as respiration, photosynthesis, and metabolism. They are also used in various industrial applications, such as corrosion control, bleaching, and electroplating.

Exothermic Reaction:

An exothermic reaction is a type of chemical reaction that releases heat or energy to the surroundings. In other words, the products of the reaction have less energy than the reactants, and the excess energy is released in the form of heat, light, or sound. Examples of exothermic reactions include combustion, oxidation, and neutralization reactions.

Endothermic Reaction:

An endothermic reaction is a type of chemical reaction that absorbs heat or energy from the surroundings. In other words, the products of the reaction have more energy than the reactants, and the energy is absorbed from the surroundings to make up for the difference. Examples of endothermic reactions include thermal decomposition, photosynthesis, and the melting of ice.

In both exothermic and endothermic reactions, energy is involved. However, the direction of the energy transfer is opposite in the two types of reactions. In an exothermic reaction, energy is released, while in an endothermic reaction, energy is absorbed. The energy change in a chemical reaction can be determined by measuring the change in temperature, enthalpy, or other thermodynamic properties.

Reactants:

Reactants are the starting materials or substances that participate in a chemical reaction. They are written on the left-hand side of a chemical equation and are consumed or used up during the reaction. Reactants are typically written using chemical symbols and formulas to represent the elements and compounds involved in the reaction.

Products:

Products are the new substances that are formed as a result of a chemical reaction. They are written on the right-hand side of a chemical equation and are produced from the reaction. Products are typically written using chemical symbols and formulas to represent the elements and compounds that are formed during the reaction.

In a chemical reaction, reactants are transformed into products through the breaking and formation of chemical bonds. The reaction is often described using a chemical equation, which shows the reactants and products and the stoichiometric coefficients that balance the equation. The reactants and products can be solids, liquids, or gases, and their properties may be different from the reactants depending on the nature of the reaction.

 

Corrosion 

Corrosion is a type of chemical reaction that occurs when a material, such as a metal, is exposed to an environment that causes it to react and deteriorate over time. In the case of metals, corrosion is often caused by the presence of oxygen, moisture, or other corrosive chemicals in the environment. 

For example:- 

the corrosion of iron, also known as rusting, occurs when iron reacts with oxygen and water to form iron oxide (rust). This process involves the transfer of electrons from the iron to the oxygen and water molecules, causing the iron to corrode and weaken over time.