Basic Concepts of Chemistry

Basic Concepts of Chemistry

• Chemistry is the science of molecules and their transformations
• It focuses on the infinite variety of molecules built from elements
• Scientific knowledge is continually being systemized to describe and understand nature
• Chemistry is sub-divided into various disciplines like physics, biology, geology, etc.
• Chemistry studies the preparation, properties, structure, and reactions of matter
• Early chemistry was driven by the search for the Philosopher's Stone and the Elixir of Life
• Ancient Indian practices involved knowledge of chemical processes and techniques, including metallurgy, medicine, and the manufacture of various materials
• Copper metallurgy began in the chalcolithic period
• Understanding tanning & dyeing techniques developed in India
• Ancient Indians had knowledge of sulphuric, nitric and various metal oxides
• Knowledge of gunpowder & fireworks existed
• Modern Chemistry developed in 18th century Europe, after alchemical traditions were introduced by the Arabs
• Alchemists and Iatrochemists made significant contributions to modern chemistry
• Chemistry plays a crucial role in various fields like weather patterns, computer operation, manufacturing fertilizers, dyes, polymers, drugs, soaps, metals and alloys, & new material development.
• Chemistry significantly impacts national economies and improving quality of life (fertilizers, pesticides, life-saving drugs).
• Modern chemistry addresses environmental challenges like greenhouse gases and the development of safer alternatives to environmentally harmful substances
• Chemistry is essential for understanding matter, its composition, structure, properties & interactions

Nature of Matter

• Matter is anything that has mass and occupies space.
• Matter exists in three physical states: solid, liquid and gas.
• Solids have a definite volume and shape
• Liquids have a definite volume and take the shape of their container.
• Gases have neither a definite volume or shape, filling the entire container they are in.
• Matter can be classified as: mixtures or pure substances.
• Pure substances have a fixed composition and properties and are classified further as elements and compounds.
• Mixtures have variable compositions and contain different pure substances in any proportions.
• Mixtures are classified into homogeneous and heterogeneous mixtures.
• Homogeneous mixtures have uniform composition.
• Heterogeneous mixtures have non-uniform composition.

Properties of Matter and Measurement

• Every substance has unique physical and chemical properties.
• Physical properties can be observed without changing the identity or composition of the substance
• Chemical properties require a chemical change to occur to observe
• Measurements of physical properties do not always involve chemical change
• Measurement of the properties of matter involves numbers and units.

Measurement of Physical Properties

• Standardized units are required for quantitative measurement and investigation
• The English and Metric system were earlier used in different parts of the world
• There is a need for a standard global measuring system.
• The International System of Units (SI) system is used: it contains seven base units and prefixes for multiples and submultiples.

Mass, Weight and Volume

• Mass refers to the amount of matter in an object, while weight is the force exerted on an object by gravity
• The SI Unit of Mass is the kilogram, it is a constant
• The SI Unit of Volume is the cubic meter (m³) usually measured in smaller units like cm³, and dm³ (liter)
• Density is Mass per unit Volume

Other Facts

• Scientific notation is used to express extremely large and small numbers.
• Significant figures indicate the degree of uncertainty in the measurement
• Precision refers to the closeness of repeated measurements
• Accuracy refers to how close the measurements are to the true value
• Stoichiometry deals with calculations of quantities of reactants and products in chemical reactions
• Balanced chemical equations help calculate relative amounts or masses of reactants and products.
• Limiting reagent is the reactant that limits the amount of product that can be formed, consumed first limiting the reaction.

States of Matter

• Matter exists in three physical states: solid, liquid and gas; each with a distinctive arrangement of particles.
• The particles in solids are closely packed and have a fixed arrangement
• The particles in liquids are relatively close but not in a fixed arrangement.
• The particles in gases are widely spaced and move freely.
• These three states are interconvertible through changes in temperature and pressure

Law of Chemical Combination

• Law of conservation of mass - there is no net change in mass during chemical or physical changes.
• Law of definite proportions - A compound always contains same elements combined in a fixed ratio by mass
• Law of multiple proportions - When two elements combine to form more than one compound, the masses of an element which combine with a fixed mass of other element are in a ratio of small whole numbers
• Gay-Lussac's law of gaseous volumes - When gases combine or are formed, the volumes of gaseous reactants and products are in a simple whole number ratio, provided that the temperature and pressure are constant

Atomic & Molecular Masses /Mole Concept

• Atomic mass is the relative mass of an atom compared to 1/12th of the mass of a carbon-12 atom.
• Molecular mass is the sum of atomic masses of all atoms in a molecule.
• Formula mass is similar to molecular mass but for ionic compounds
• Mole is the amount of substance that contains 6.022 × 10²³ entities (atoms, molecules or ions).
• Avogadro's number (N_A), represents the number of particles (atoms, molecules, ions) in one mole (6.022 x 10²³)
• Molar mass is the mass of one mole of a substance (numerically equal to the atomic /molecular/ formula mass in grams)

Stoichiometry

• Stoichiometry is the quantitative relationship between reactants and products in chemical reactions