Some Basic Concepts of Chemistry Class 11

9 minute read
Some Basic Concepts of Chemistry Class 11

The students of the science stream must be aware that chemistry is a branch of science that deals with the composition, structure, properties, and characters of different matter. Chemistry is also known as the science of atoms and molecules. While knowing your class 11 chemistry syllabus is important is also essential to be through with the course. This blog will cover some vital and important study notes related to chapter 1 of some basic concepts of Chemistry class 11.

Some Basic Concepts of Chemistry Class 11

Here are the topics that you should prepare for Class 11 Chemistry Chapter 1- Basic Concepts of Chemistry:

  • The International System Of Units (SI)
  • Molecular Mass
  • Reactions In Solutions
  • Atomic Mass
  • Percentage Composition
  • Scientific Notation
  • Law Of Definite Proportions
  • Nature Of Matter
  • Mass And Weight
  • Significant Figures
  • Law Of Multiple Proportions
  • Mole Concept And Molar Masses
  • Uncertainty in Measurement
  • Avogadro Law
  • Dimensional Analysis
  • Law Of Conservation Of Mass
  • Formula Mass
  • Gay Lussac’s Law Of Gaseous Volumes
  • Average Atomic Mass
  • Laws Of Chemical Combinations
  • Dalton’s Atomic Theory
  • Importance Of Chemistry
  • Empirical Formula For Molecular Formula
  • Stoichiometry And Stoichiometric Calculations
  • Atomic And Molecular Masses
  • Limiting Reagent
  • Properties Of Matter And Their Measurement

Importance of Chemistry

Studying chemistry is lucrative from many perspectives and there are numerous benefits of studying it. Being a central science, chemistry is used in every aspect of a person’s life from the food consumed to the products used. The improvement of chemical science has altered the premise of current medication. With ever-increasing research in chemistry, marvel drugs like penicillin and streptomycin have been developed. Enlisted below are the manifold reasons for pursuing a degree in chemistry and establishing a career in the field of chemical science. 

  • It teaches useful skills that can be used in practical life when dealing with chemicals.
  • With more students pursuing chemistry, there has been unprecedented progress in the production of new medicines for treating fatal diseases
  • A student gets acquainted with the various chemicals present in the environment and thus has a better understanding of how natural processes occur.
  • A command over chemistry helps in distinguishing between chemicals and using them for the appropriate reason.
  • Chemistry is a popular course and there exists a large number of professions that a person with a degree in chemistry can work. 

Branches of Chemistry 

In chapter 1 of Some Basic Concepts of Chemistry Class 11, we got to know about the 7 branches of chemistry. These are :

  • Organic Chemistry deals with the study of carbon compounds, especially hydrocarbons and their derivatives.
  • Inorganic chemistry relates to the study of compounds of all other elements except carbon. A major focus is the study of minerals in the Earth’s crust.
  • Physical chemistry refers to explaining the fundamental principles governing various chemical phenomena is the primary concern of this branch of chemistry. It is fundamentally concerned with different laws and theories of the different branches of chemistry.
  • Industrial Chemistry deals with industrial processes.
  • Analytical Chemistry is the branch of chemistry responsible for the qualitative and quantitative analysis of different substances.
  • Biochemistry focuses on the ongoing chemical changes in the bodies of living organisms, plants and animals.
  • Nuclear Chemistry is about nuclear reactions, such as nuclear fission, nuclear fusion, transmutation processes, etc. 

Properties Of Matter

Chapter 1 of some basic concepts of Chemistry Class 11 also discusses the properties of different substances and their unique characteristics and properties. Having said that, the properties can be divided into two types:

  • Physical properties can be measured or observed without changing the identity or the composition of the substance or matter. Examples can be changes in colour, odour, melting point, boiling point, density, etc. 
  • Chemical properties on the other hand are referred to as the characteristic reactions of different materials, including acidity or basicity, combustibility, etc. Many properties of matter, such as length, area, volume, etc., are of a quantitative nature.

The International System of Units

The International System of Units also known as Le Systeme International d’Unites in French is one of the most important basic concepts of chapter 1 and some basic concepts of chemistry Class 11. Abbreviated as SI, it was established by the 11th General Conference on Weights and Measure. The SI system has 7 basic units.

Base Physical Quantity  Symbol for quantity  Name of the SI unit  The symbol for SI unit 
Length  l metre m
mass m kilogram kg
time t second s
Electric current  I ampere A
Amount of substance  n mole mol
Luminous intensity  IV candela cd
Thermodynamic temperature T Kelvin  K

Physical Classification of Matter

Here is a table for you that will help you to revise this sub-topic of chapter 1 on some basic concepts of Chemistry Class 11. 

Properties  Solid  Liquid  Gas
Shape  Definite  Indefinite  Indefinite 
Volume  Definite  Definite  Indefinite 
Arrangement of Molecules  Arranged orderly  Free to move within the volume  Free to move
Intermolecular force of attraction Very high Moderate Negligible  

Intermolecular space Very small Moderate  Huge 
Expansion on heating Very little Very little Highly expand
Compressibility Not compressible Not compressible Highly compressible
Rigidity Very rigid Not rigid  Not rigid
Fluidity Cannot flow Can flow Can flow
Diffusion Can diffuse  Can diffuse Can diffuse   

Chemical Classification of Matter

  1. Compounds: a compound is a form of pure substance which is made up of two or more elements combined in a definite proportion by mass. It could be split by suitable chemical methods. 
  1. Elements: an element is the simplest form of pure substance or matter that cannot be split into two or simpler substances by chemical reactions and methods like compounds. There are 114 known elements, 92 of which are naturally occurring and the remainder have been artificially prepared. The elements are then classified into metal, nonmetal and metalloid.
  1. Homogeneous mixtures: it is a form of mixing which has the same composition throughout the sample. The constituents of these mixtures cannot be viewed under a powerful microscope. We call them solutions too. Examples of homogenous mixtures are air, seawater, petrol, brass and more.
  1. Heterogeneous mixture: contrary to a homogeneous mixture, heterogeneous mixtures are made up of two or several parts (phases), which have different compositions. These mixtures have visible dividing lines between the different constituents and can be seen with the naked eye, for example, sand and sugar, chalk powder or in water, and more. 

Significant Figures

The concept of significant figures in chapter 1 of some basic chemistry class 11 explains that the reliability of a measure is given by the number of digits used to represent it. To put it more precisely, we use figures which are known with certainty. These numbers are known as significant figures. They contain all specific figures plus a questionable figure in a number.

Rules for Determining the Number of Significant Figures

The next important topic in chapter 1 of some basic concepts of chemistry class 11 is some rules to determine the number of significant figures. These rules are as follows:

  • All nonzero numbers are significant.    For example, 7.5 has two significant digits, whereas 7.15 has three significant digits. The decimal shall not determine the number of significant figures.
  • A zero becomes significant if it arrives between non-zero numbers. For example, 3.098 has four significant figures, and 4.002 has three significant figures.
  • Zeros at the beginning of a number are not significant. For example, 0.032 has only 2 significant figures, while 0.005 has one significant figure.
  • Any zeros on the right of a number are significant. For instance, 18.0 has three significant digits, while 18.00 has four significant digits. Zeros at the end of a number without a decimal point are ambiguous.
  • In exponential notations, the numerical part represents the number of significant figures. For example, 0.00095 is expressed as 9.5 x 10-4 in terms of scientific notations. The number of significant figures in this number is 2, while in Avogadro’s number (6.023 x 1023) it is four.
  • The decimal place does not count for the number of significant figures. For example, the number 745608 has six significant figures but can be written in different ways, such as 745.608 or 0.745608 or 74.5608, all having the same number of significant figures.

Explore: Laws of Motion Class 11: Notes and Questions

Laws Of Chemical Combinations

Let us have a look at the law of chemical combinations in some basic concepts of chemistry class 11.

Name of the law  Proposed/Given  Year  Description 
Law of Conservation
of Mass
Antoine Lavoisier 1789 The law of conservation of mass
states that matter (mass) can neither
be created nor destroyed
Law of Definite Proportions
OR Law of Constant
Louis Proust 1799 A chemical compound always consists
of the same elements combined together
in the same ratio, irrespective of the
method of preparation or the source
from where it is taken.
Law of Multiple Proportions Dalton 1803 The law of multiple proportions states
that when two elements combine to form
two or more compounds, then the different masses of one element, which combine
with a fixed mass of the other, bear a
simple ratio to one another.
Avogadro Law Avogadro 1811 Avogadro law states that equal volumes
of gases at the same temperature and
pressure should contain an equal number
of molecules.
Gay Lussac’s Law of Gaseous Volumes Gay Lussac 1808 When gases combine or are produced
in a chemical reaction, they do so in
a simple ratio by volume provided
all gases are at the same temperature and pressure.

Dalton’s Atomic Theory

Dalton’s Atomic theory of chapter 1 some basic concepts of chemistry class 11 states that all substances consist of small indivisible particles known as atoms. Atoms of the same element have similar shapes, sizes, masses and other properties. The atoms of the various elements differ in all aspects. The atom is the smallest unit of chemical combinations. Atoms combine into single whole-number ratios to form compound atoms called molecules. Atoms cannot be created, divided or destroyed in the course of a chemical or physical change.

Must Read: Class 11 Gravitation Notes and Important Question

Some Basic Definitions And Terminologies 

Here are some basic definitions and terminologies which are important in some basic concepts of chemistry class 11. 

  • Atomic Mass Unit: An atom mass unit is defined as a mass exactly equal to one-twelfth of the mass of a carbon atom -12. 1 amu = 1.66056×10–24 g. The “amu” has been changed to the “u”, called the unified mass.
  • Atomic Mass: The average relative mass of an atom of an element concerning the mass of a carbon atom -12 taken as 12.
  • Gram Atomic Mass: It is called the quantity of an element whose mass in grams is numerically equal to its atomic mass. In simple terms, the atomic mass of an element expressed in grams is the gram atomic mass or gram atom. For example, the atomic mass of oxygen is 16 AMU. Therefore, the gram atomic mass of oxygen is 16 g.
  • Molecular Mass: The molecular mass of a substance is defined as the average relative mass of its molecule concerning the mass of a C-12 atom taken as 12. It expresses how frequently the molecule of a substance is heavier than 1/12th of a carbon atom’s mass.
  • Gram Molecular Mass: An amount of substance with a mass in grams numerically equal to its molecular mass is called a gram molecular mass of that substance. Simply put, the molecular mass of a substance expressed in grams is called gram molecular mass. For instance, oxygen has a molecular mass of 32 AMU. Therefore, the gram molecular mass of oxygen is 32 g.
  • Formula Mass: Summation of the atomic masses of the elements present in one formula unit of a compound. It is used for ionic compounds.
  • Molar Mass: The mass of one mole of a substance in grams is called its molar mass.
  • Molar Volume: it is the volume occupied by one mole of any substance. VM denotes it. The unit of molar volume is liter per mol or milliliter per mol.
  • Empirical Formula: it is a formula representing the simplest whole-number ratio of the various atoms present in a compound. For example,  CH is the empirical formula of benzene.
  • Molecular Formula: is a formula that shows the exact number of different types of atoms present in a given molecular compound. For example, C6H6 is the molecular formula of benzene.

Some Basic Concepts of Chemistry PDF

Download the NCERT syllabus for Class 11 chemistry from the link given below:

Download Chemistry Class 11 Chapter 1 Here

Types of Questions in Chapter 1 Some Basic Concept: Chemistry Class 11

  • Numerical problems in calculating the molecular weight of compounds
  • Numerical problems in calculating mass per cent and concentration
  • Questions on empirical and molecular formulae
  • Questions on molarity molality and molarity
  • Additional problems with the mole theory (such as percentage composition and expressing concentration in parts per million)
Credit: Physics Wallah – Alakh Pandey


What are the basic concepts in Chemistry?

Atomic number and mass, molecular mass, chemical equation, and mole concept are some of the basic concepts in Chemistry.

Which chapters should I study first in Class 11 Chemistry?

Structure of Atoms, Molecular Structure and Chemical Bonding, and Thermodynamics are some of the important chapters, to begin with. These chapters are very important in the Class 12 ISC board examination as well.

What are some basic concepts of Chemistry class 11 ICSE?

Some of the basic concepts of Class 11 chemistry are as follows:
The International System Of Units (SI)
Molecular Mass
Reactions In Solutions
Atomic Mass
Percentage Composition
Scientific Notation
Law Of Definite Proportions
Nature Of Matter

This brings us to the end of this blog on some basic concepts of chemistry class 11. We hope that the blog will help you during your exams to quickly brush up on some basic concepts of chemistry and other study notes. For more such blogs, study notes and amazing reads, stay tuned to Leverage Edu.

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