Unit 1: Some Basic Concepts of Chemistry

Introduction to Chemistry

• Science is about understanding and systematizing knowledge of nature.
• Chemistry: Studies preparation, properties, structure, and reactions of materials.
• Changes in substances are common, e.g., curdling of milk, rusting of iron.

Development of Chemistry

• Ancient knowledge present in India, China, etc.
• Chemistry developed as alchemy and iatrochemistry (1300-1600 CE).
• Modern chemistry emerged in the 18th century in Europe.

Contributions of India

• Ancient India had knowledge of metallurgy, medicine, etc. (Rasayan Shastra).
• Techniques included metal extraction, e.g., copper, iron.
• Ancient texts like Charaka Samhita, Sushruta Samhita discussed chemicals.
• Concepts of Rasopanishada, Nagarjuna's work on mercury.

Importance of Chemistry

• Central role in science, affects weather, medicine, technology.
• Key to national economy, development of new materials.
• Addresses environmental issues, e.g., alternatives to CFCs.

Nature of Matter

• Matter: Anything with mass and occupies space.
• Exists in three states: solid, liquid, gas.
• States are interconvertible with temperature/pressure changes.

Classification of Matter

• Mixtures vs. Pure substances.
• Mixtures: Homogeneous (uniform) or heterogeneous (non-uniform).
• Pure substances: Elements (single type of atoms) or compounds (fixed ratio of different atoms).

Properties and Measurement

• Physical properties: measurable without identity change (color, melting point).
• Chemical properties: require chemical changes (combustibility).
• Measurements use SI Units (e.g., metre, kilogram) and scientific notation for precision.

Laws of Chemical Combination

• Law of Conservation of Mass: Mass is conserved in chemical reactions (Lavoisier).
• Law of Definite Proportions: A compound always has the same proportion of elements by mass (Proust).
• Law of Multiple Proportions: Ratios of masses of two elements forming different compounds are simple (Dalton).
• Gay Lussac's Law: Gases combine in simple volume ratios.
• Avogadro's Law: Equal volumes of gases have equal molecules at the same temperature and pressure.

Atomic and Molecular Masses

• Atomic Mass: Relative masses of atoms based on carbon-12.
• Molecular Mass: Sum of atomic masses in a molecule.
• Formula Mass: Used for ionic compounds (e.g., NaCl).

Mole Concept

• Mole: SI unit for amount of substance (6.022 x 10^23 entities).
• Molar Mass: Mass of 1 mole numerically equal to atomic/molecular mass in units.

Stoichiometry

• Calculations based on balanced chemical equations.
• Limiting Reagent: Determines the amount of product formed.
• Solutions: Concentration measured in mass percent, mole fraction, molarity, and molality.

Exercises

• Includes calculations of molar mass, percent composition, empirical and molecular formulas, conversion factors, and stoichiometric problems.