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Chemistry Principles and Concepts Overview

Apr 25, 2025

Chemistry Lecture Notes

Section A: Principles of Chemistry

1) States of Matter

1.1) Definition and Properties

  • Matter: Anything with mass occupying space.
  • States: Solid, liquid, gaseous, determined by physical properties (e.g., color, odour).
  • Particulokinetic Theory:
    • Matter comprises particles in constant motion.
    • Balance between forces of repulsion and attraction keeps particles together.
  • Evidence: Crystals, diffusion, Brownian motion, osmosis.

1.2) Properties of Different States

  • Solids: Definite shape, constant volume, not compressible.
  • Liquids: Variable shape, constant volume, slightly compressible.
  • Gases: Variable shape and volume, easily compressible.

1.3) Changes of State

  • Melting: Solid to liquid.
  • Evaporation: Liquid particles escape as vapor.
  • Boiling: Liquid to vapor at boiling point.
  • Condensation: Gas to liquid.
  • Freezing: Liquid to solid.
  • Sublimation: Solid directly to gas.

2) Mixtures and Separations

2.1) Definitions

  • Pure Substance: Single element/compound with constant properties.
  • Mixture: Two or more substances not chemically combined.
    • Homogeneous: Same composition throughout.
    • Heterogeneous: Non-uniform composition.

2.2) Types of Mixtures

  • Solutions: Solute and solvent thoroughly mixed, do not separate.
  • Suspensions: Components separate over time, visible particles.
  • Colloids: Intermediate particle size, do not separate on standing.

2.4) Solubility

  • Solubility depends on solute and solvent nature, temperature, pressure.
  • Saturated Solution: Maximum solute dissolved.

2.5) Separation Techniques

  • Filtration, Sublimation, Solvent Use: To separate components based on properties.
  • Distillation: To separate based on boiling points.
  • Chromatography: To separate based on movement through a medium.

3) Atomic Structure

3.1) Basic Concepts

  • Atoms: Smallest part showing element properties.
  • Electrons move in shells around nucleus.
  • Valence electrons participate in bonding.

3.2) Subatomic Particles

  • Protons: Positive charge, relative mass = 1.
  • Neutrons: No charge, relative mass = 1.
  • Electrons: Negative charge, relative mass ≈ 0.

3.6) Isotopes

  • Same element, different neutron numbers.
  • Used in medicine and energy generation.

4) Periodic Table and Periodicity

4.1) General Trends

  • Arrangement based on atomic number.
  • Periods: Rows with increasing electron shells.
  • Groups: Columns with similar properties.

4.4) Period 3 Elements

  • Trends in atomic radius, electronegativity, melting/boiling points.

5) Structure and Bonding

5.1) Ionic and Covalent Bonds

  • Ionic Bonds: Transfer of electrons, forming ions.
  • Covalent Bonds: Sharing electrons between non-metal atoms.

5.4) Metallic Bonding

  • Positive ions in a 'sea' of electrons.

5.6) Properties of Compounds

  • Ionic Compounds: High melting points, conduct electricity when molten.
  • Covalent Compounds: Lower melting points, don't conduct electricity.

6) Mole Concept

6.1) Definitions

  • Mole: Amount of substance with Avogadro's number of particles.
  • Calculations involving moles, mass, and number of particles.

7) Acids, Bases, and Salts

7.1) Properties of Acids and Bases

  • Acids produce H+ ions in solution.
  • Bases accept H+ ions.
  • pH scale indicates acidity/alkalinity.

7.4) Reactions of Acids

  • With metals, bases, carbonates.

8) Oxidation-Reduction Reactions

8.1) Bleaching and Browning

  • Bleaching agents as oxidizing agents.
  • Browning of fruits due to enzymatic reaction.

8.3) Oxidation Numbers

  • Rules for assigning oxidation states.

9) Electrochemistry

9.1) Conductivity

  • Metallic Conduction: Via free electrons.
  • Electrolytic Conduction: Via ions in molten/aqueous solutions.

9.9) Applications

  • Electroplating, electrorefining, and anodizing.

10) Rates of Reaction

10.1) Factors Affecting Rates

  • Concentration, pressure, temperature, catalysts, surface area.

11) Energetics

11.1) Exothermic and Endothermic

  • Exothermic: Releases heat, ΔH negative.
  • Endothermic: Absorbs heat, ΔH positive.