CBSE Class 11 Chemistry Notes Chapter 1 Some Basic Concepts of Chemistry

CBSE Class 11 Chemistry Notes Chapter 1: CBSE Class 11 Chemistry Notes Chapter 1 talks about the basic ideas of chemistry. It explains what chemistry is and what it studies. Chemistry is all about studying different kinds of substances and how they change. The chapter begins by talking about matter, which is anything that takes up space and has weight.

Some Basic Concepts of Chemistry Class 11 Notes

Laws of Chemical Combination

Law of Conservation of Mass: This law, proposed by Antoine Lavoisier, states that the total mass of substances involved in a chemical reaction remains constant. In other words, mass is neither created nor destroyed during a chemical reaction; it is merely rearranged from reactants to products.

Law of Definite Proportions: Also known as the Law of Constant Composition, this law was formulated by Joseph Proust. It states that a given chemical compound always contains its constituent elements in fixed proportions by mass. Regardless of the source or method of preparation, the ratio of elements in a compound is constant.

Law of Multiple Proportions: This law, proposed by John Dalton, states that when two elements form more than one compound, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers. This law illustrates the concept of combining ratios between elements in different compounds.

Gay-Lussac's Law of Combining Volumes: Formulated by Joseph Louis Gay-Lussac, this law states that when gases react, they do so in volumes that bear simple whole-number ratios to one another and to the volumes of the gaseous products, provided all volumes are measured under the same conditions of temperature and pressure.

Avogadro's Law: This law, proposed by Amedeo Avogadro, states that equal volumes of gases, at the same temperature and pressure, contain the same number of molecules. This law is essential for understanding the concept of the mole and the relationship between volume and amount of gas.

Classification of Matter at Macroscopic Level

Solids: Solids have a definite shape and volume. The particles in solids are closely packed together and have strong intermolecular forces that hold them in a fixed position. This arrangement gives solids their rigidity and resistance to compression. Examples of solids include metals, wood, glass, and rocks.

Liquids: Liquids have a definite volume but take the shape of their container. The particles in liquids are less closely packed compared to solids, allowing them to move past one another. Liquids flow and can be poured, but they do not expand to fill the entire volume of the container. Examples of liquids include water, milk, oil, and gasoline.

Gases: Gases have neither a definite shape nor volume. The particles in gases are spaced far apart and move freely in all directions. Gases completely fill the container they occupy and expand to fill any available space. They are highly compressible and exert pressure on the walls of the container. Examples of gases include oxygen, nitrogen, carbon dioxide, and hydrogen.

Properties of Matter

Physical Properties:

• Color: The visual appearance of a substance.
• Odor: The characteristic smell of a substance.
• Density: The mass per unit volume of a substance.
• Melting Point: The temperature at which a solid changes into a liquid.
• Boiling Point: The temperature at which a liquid changes into a gas.
• Solubility: The ability of a substance to dissolve in a solvent.
• Conductivity: The ability of a substance to conduct heat or electricity.
• Malleability: The ability of a substance to be hammered into thin sheets.
• Ductility: The ability of a substance to be drawn into wires.

Chemical Properties:

• Flammability: The ability of a substance to burn or ignite.
• Reactivity: The tendency of a substance to undergo chemical reactions with other substances.
• Corrosiveness: The ability of a substance to cause deterioration or damage to other materials.
• Toxicity: The degree to which a substance can harm living organisms.
• Oxidation State: The number of electrons gained, lost, or shared by an atom in a compound.

Measurement

Physical Quantities

S.I. Units

Here are the seven base SI units:

1. Meter (m) - for length
2. Kilogram (kg) - for mass
3. Second (s) - for time
4. Ampere (A) - for electric current
5. Kelvin (K) - for temperature
6. Mole (mol) - for amount of substance
7. Candela (cd) - for luminous intensity

Some Important Definition

Mass and Weight:

• Mass refers to the amount of substance present in an object. It remains constant regardless of the location.
• Weight, on the other hand, is the force exerted by gravity on an object. It can vary based on the gravitational field strength.
• The SI unit for mass is the kilogram (kg), while the SI derived unit for weight is the Newton (N).

Volume:

• Volume is the measure of the three-dimensional space occupied by an object or substance.
• It's commonly quantified using SI derived units, typically cubic meters (m^3).

Density:

• Density represents the mass of a substance per unit volume.
• It's denoted by the symbol ρ (rho), and its SI unit is kilograms per cubic meter (kg/m^3).

Temperature:

• Temperature quantifies the degree of hotness or coldness of a substance.
• There are three common temperature scales: Celsius (°C), Fahrenheit (°F), and Kelvin (K).
• Celsius and Fahrenheit are related by the formula °F = (9/5) * °C + 32, while Kelvin is related to Celsius by K = °C + 273.15.

Law of Chemical Combination

Law of Conservation of Mass:

• In a chemical reaction, the total mass of the reactants is equal to the total mass of the products.
• Antoine Lavoisier proposed this law in 1789.

Law of Constant / Definite Proportions:

• The proportions of elements in a compound are fixed and constant.
• Joseph Proust formulated this law.

Law of Multiple Proportions:

• When elements combine to form compounds, their masses combine in simple whole-number ratios.
• This principle was introduced by Dalton in 1803.

Law of Reciprocal Proportions:

• When two elements combine with a third element, their mass ratios are either the same or simple multiples of each other.
• Richter proposed this law in 1792.

Gay Lussac’s Law of Gaseous Volumes:

• The volumes of gaseous reactants and products in a chemical reaction can be expressed as simple whole-number ratios.
• Gay-Lussac formulated this law in 1808.

Avogadro Law:

• Equal volumes of gases at the same temperature and pressure contain the same number of molecules.
• Proposed by Avogadro in 1811.

Dalton’s Atomic Theory

Indivisible Atoms: Matter is composed of indivisible particles called atoms. These atoms are the smallest units of matter and cannot be divided further by chemical means.

Identical Properties of Atoms: All atoms of a given element are identical in their properties, including mass. Atoms of different elements have different properties and differ in mass.

Fixed Ratios in Compounds: Compounds are formed when atoms of different elements combine in fixed, whole-number ratios. These ratios are characteristic of each compound and remain constant regardless of the source or method of preparation.

Conservation of Atoms: Chemical reactions involve the reorganization of atoms. Atoms are neither created nor destroyed during a chemical reaction; they simply rearrange to form new substances.

Atom

• Atomic mass is the mass of a single atom of an element, measured in atomic mass units (amu) or unified mass (u).
• 1 amu or u is defined as 1/12th of the mass of one atom of carbon-12 (C12).

Method 2: Molar Atomic Mass:

• The mass of 6.022 × 10^23 atoms of an element measured in grams is known as the molar atomic mass.
• This quantity is numerically equal to the atomic mass measured in amu.
• When atomic mass is expressed in grams, it's referred to as the molar atomic mass.
• 6.022 × 10^23 is known as Avogadro's number.
• This number of atoms (6.022 × 10^23) is also called 1 mole of atoms.
• A mole is a unit of measurement representing a specific number, just like a dozen represents 12 items and a million represents 10^6 items.

CBSE Class 11 Chemistry Notes Chapter 1 PDF

You can access the PDF for CBSE Class 11 Chemistry Notes Chapter 1 "Some Basic Concepts of Chemistry" from the link provided below. This PDF covers all the important topics discussed in the chapter, including matter, types of matter, laws of chemical combination, and the concept of the mole.