Chemical Reactions and Equations Class 10 Notes

Chemical Reactions

Consider the following scenarios in your everyday life and then think about what happens when:

• You end up leaving milk outside during the summer
• Fermentation of grapes
• A pan/ an iron tawa, or a nail is left bare in a humid atmosphere
• Food digests in the body
• Food is being cooked
• Respiration

In all the scenarios mentioned above, the identity and nature of the initial substance are changed. You may have already learnt about chemical and physical matter changes in your previous classes. When a chemical change occurs, we say a chemical reaction occurs. A chemical reaction takes place when one or more reactants change into one or more products. In a chemical reaction, what happens is that the basic atoms of the reactants are reorganised, which leads to the formation of different substances as products.

From rust to decomposition, chemical reactions offer a detailed insight into how molecular interactions and changes occur. Our article can be used as class 10 science chapter 1 notes that explain how a specific substance can change form.

Chemical reactions are changes in which the reactants change into products by breaking or making bonds (or both) between various atoms. A chemical reaction causes a group of chemical components to convert into another. Chemical reactions are described as variations in the electrons’ locations in the breaking and formation of chemical bonds between different atoms, with absolutely no change in the nucleus, and are defined using certain chemical equations. A chemical reaction occurs at an estimated rate at specific temperatures and concentrations. The reaction speeds frequently rise as the temperature increases as more thermal energy is present to achieve the activation energy needed to disrupt the bonds between the atoms.

Physical and Chemical Changes

The following is described in class 10 chemistry chapter 1 notes below.

Chemical change: A chemical change takes place when one or more than one new substances with new chemical and physical properties are formed. For example, when iron reacts with copper sulphate, two new substances are formed: copper and ferrous sulphate.

Physical change: A physical change occurs when there is a change in the colour or the state of the substance, but no new substance is formed. For example, when boiling water is converted to steam, no new substance is formed (even if water and steam may look different, they react in the same manner reacting with a piece of Na and also giving exactly the same products). Thus, this change only includes a change of state, i.e. from liquid to vapour.

Kinds of Chemical Reactions

On considering different factors, chemical reactions can be grouped into various categories, for example:

• Combination: Two elements or one element and one compound or two compounds combine to give one product.

• Single Displacement: A highly reactive element displaces or disrupts a less reactive element from its solution or compound. 

• Double displacement: Between the reactants, an exchange of ions takes place to create new products.

• Redox: This takes place when the oxidation states of the substance change. A substance is considered to be oxidised if it obtains oxygen while undergoing a reaction. A substance is considered to be reduced if it loses oxygen while undergoing a reaction.

• Exothermic: Heat evolves during a reaction.
• Endothermic: Heat is absorbed during a reaction.
• Precipitation: Process of transforming a dissolved substance into an insoluble solid

Chemical Equations Class 10 Notes

The word equation is described as a chemical reaction articulated in words instead of using a chemical formula. It aids in identifying the products and reactants in a chemical reaction. Chemical reactions are defined using a word equation, which is a shorter method of expressing them. The reactants’ names are displayed on the left-hand side in a word equation. If more than one reactants are present, then the reactant names are separated by using the plus ( ) sign. The products in a chemical equation are displayed on the right-hand side of the word equation. If more than one products are available, then the product names are separated by a plus ( ) sign. For example,

Chlorine Sodium → Sodium chloride

The equation above means: “Chlorine reacts with sodium to give sodium chloride.”

Symbols of Elements and their Valencies

A symbol is described as the chemical code for any element. In chemistry, each element has either a one or a two-letter atomic symbol. This symbol is the shortened form of its name. Valency is described as combining the capacity of any element. A valency can also be considered as the total number of electrons that are lost, gained or shared by an atom in combination with another atom forming a molecule.

Writing Chemical Equations

Representing chemical reactions in terms of chemical formulae and symbols of the products and reactants is termed a chemical equation. 

• The symbol for liquids is “l.”
• The symbol for solids is “s.”
• The symbol for gases is “g.”
• The symbol for aqueous solutions is “aq.”
• The symbol for the precipitate formed in the reaction is represented by “↓”
• The symbol for gas formed in the reaction is represented by “↑”

Balancing a Chemical Reaction

Law of Mass Conservation: Atoms cannot be created or even destroyed in any chemical reaction. Thus, the total number of atoms in each element on the left side of a chemical equation, which is the reactants side has to be equal to the total number of atoms present on the right side of the chemical, which is the products side. 

In simpler words, the total products created in a chemical reaction should be equal to the total mass of the reactants that have been a part of the chemical reaction.

Balanced Chemical Equation

A chemical equation in which the total number of atoms of each element on the reactants side is the same as that of the products side is termed a balanced chemical equation.

Coefficients are used to balance chemical equations. A coefficient is nothing but a numerical value added right at the front of a chemical formula or a symbol. It represents the total number of molecules or atoms of the material that are involved in the process. For example:

For example,

HCl + Zn → H2 + ZnCl2

Balanced Equation is

Zn + 2HCl → ZnCl2 + H2

Summary

This article discusses the concept of chemical reactions and equations and how to balance chemical equations. , their properties, examples, and their uses with special reference to chemical reactions and equations notes for students and teachers alike.