H1 Chemistry: Course Entries

Core Idea 1: Matter

1. Atomic Structure

• The Nucleus of the Atom: Composed of neutrons and protons, characterized by nucleon numbers (mass number) and proton numbers (atomic number). Isotopes are atoms of the same element with different neutron numbers.
• Electrons: Reside in electronic energy levels with varying energies. Ionisation energies represent the energy required to remove electrons from an atom. Atomic orbitals describe the probability of finding an electron in a specific region. Extranuclear structure refers to the arrangement of electrons outside the nucleus.

Core Idea 2: Structure and Properties

2. Chemical Bonding

• Types of Bonding: Chemical bonds, electrostatic in nature, include ionic bonding (electrostatic attraction between oppositely charged ions), covalent bonding (electrostatic attraction between shared electrons and positively charged nuclei), metallic bonding (electrostatic attraction between a lattice of positive ions and delocalized electrons), and coordinate (dative covalent) bonding (where both shared electrons originate from the same atom).
• Molecular Shapes and Bond Angles: Valence Shell Electron Pair Repulsion (VSEPR) theory predicts molecular shapes (e.g., linear, trigonal planar, tetrahedral, trigonal pyramidal, bent, octahedral) and bond angles.
• Bond Polarities and Molecular Polarity: Electronegativity differences between atoms determine bond polarity. Molecular polarity depends on bond polarities and molecular shape.
• Intermolecular Forces: Include permanent and induced dipole interactions, and hydrogen bonding (stronger dipole-dipole interaction involving hydrogen bonded to highly electronegative atoms like N, O, or F). These forces influence physical properties like boiling point and solubility.
• Bond Energies and Bond Lengths: Bond energy refers to the energy required to break a covalent bond. Bond length is the distance between the nuclei of two bonded atoms.
• Lattice Structure of Solids: Solids can have various lattice structures (ionic, simple molecular, giant molecular, hydrogen-bonded, metallic), which influence their physical properties.
• Bonding and Physical Properties: The type of bonding and structure significantly affect a substance's physical properties (e.g., melting point, boiling point, electrical conductivity).

3. Theories of Acids and Bases

• Arrhenius Theory: Defines acids as substances that produce H+ ions in water and bases as substances that produce OH- ions in water.
• Brønsted-Lowry Theory: Defines acids as proton donors and bases as proton acceptors. Introduces the concept of conjugate acid-base pairs.
• Acid and Base Dissociation Constants (Ka and Kb): Quantify the strength of acids and bases.
• Ionic Product of Water (Kw): Represents the product of H+ and OH- concentrations in water.
• pH and Indicators: pH measures the acidity or alkalinity of a solution. Indicators are used to determine pH changes during titrations.
• Buffer Solutions: Resist changes in pH when small amounts of acid or base are added.

4. The Periodic Table

• Periodicity: Atomic and physical properties of elements show periodic trends across periods and down groups. These trends are related to electronic configuration, atomic/ionic radius, ionization energy, electronegativity, melting point, and electrical conductivity.
• Chemical Properties: Chemical properties also exhibit periodicity, including trends in oxidation numbers, bonding of oxides and chlorides, reactions with water, and acid-base behavior.
• Group Trends: Specific trends exist within groups, such as the reactivity of Group 1 elements as reducing agents and Group 17 elements as oxidizing agents, and the thermal stability of Group 17 hydrides.

Core Idea 3: Transformation

5. The Mole Concept and Stoichiometry

• Relative Masses: Relative atomic, isotopic, molecular, and formula masses are used to compare the masses of atoms and molecules.
• The Mole and Avogadro Constant: The mole is a unit for the amount of substance, related to the Avogadro constant (number of entities per mole).
• Empirical and Molecular Formulae: Empirical formula represents the simplest whole-number ratio of atoms in a compound. Molecular formula shows the actual number of atoms of each element in a molecule.
• Reacting Masses and Volumes: Stoichiometry involves calculations based on balanced chemical equations, relating reacting masses, volumes of solutions, and volumes of gases.
• Redox Processes: Involve electron transfer and changes in oxidation numbers (oxidation states). Redox equations can be constructed using half-equations.

6. Chemical Energetics: Thermochemistry

• Enthalpy Changes (ΔH): Most chemical reactions involve energy changes, primarily as heat. Exothermic reactions release heat (ΔH negative), while endothermic reactions absorb heat (ΔH positive).
• Energy Profile Diagrams: Show enthalpy changes and activation energies.
• Types of Enthalpy Changes: Include enthalpy changes of formation, combustion, and neutralization. Bond energy is the enthalpy change associated with breaking a bond. Lattice energy is the enthalpy change when gaseous ions form a solid lattice.
• Hess's Law: States that the total enthalpy change for a reaction is independent of the pathway taken. Used to calculate enthalpy changes indirectly.

7. Reaction Kinetics

• Rate of Reaction: The change in concentration of a reactant or product per unit time.
• Rate Equation and Order of Reaction: Rate equation relates the rate of reaction to the concentrations of reactants. Order of reaction indicates the dependence of the rate on the concentration of each reactant.
• Rate Constant and Half-life: Rate constant (k) is a proportionality constant in the rate equation. Half-life is the time taken for the concentration of a reactant to decrease by half.
• Factors Affecting Reaction Rate: Concentration, temperature, and catalysts influence reaction rate.
• Activation Energy: The minimum energy required for a reaction to occur.
• Catalysis: Catalysts increase reaction rate by providing an alternative pathway with lower activation energy.
• Heterogeneous Catalysts: Catalysts in a different phase from the reactants.
• Enzymes: Biological catalysts with specific activity.

8. Chemical Equilibria

• Reversible Reactions and Dynamic Equilibrium: Reversible reactions can proceed in both forward and reverse directions. Dynamic equilibrium is reached when the rates of forward and reverse reactions are equal.
• Le Chatelier's Principle: Predicts the effect of changes in conditions (concentration, pressure, temperature) on the position of equilibrium.
• Equilibrium Constants: Quantify the extent of a reversible reaction.
• Haber Process: An industrial example of the importance of chemical equilibrium.

Extension Topic: Materials

9.1 Nanomaterials

• Nanomaterials and Nanoparticles: Nanomaterials have at least one dimension on the nanoscale (1-100 nm). Nanoparticles are particles with all three dimensions on the nanoscale.
• Surface Area to Volume Ratio: Nanomaterials have a high surface area to volume ratio, which enhances properties like catalysis and interactions.
• Graphene: A nanomaterial with a single layer of carbon atoms arranged in a hexagonal lattice. Its unique structure leads to high electrical conductivity and tensile strength.
• Health and Environmental Concerns: Potential impacts of nanoparticles on human health and the environment need consideration.

9.2 Polymers

• Macromolecules: Polymers are large molecules (macromolecules) composed of repeating monomer units.
• Types of Polymers: Addition polymers are formed by the addition of monomers without loss of atoms. Condensation polymers are formed by the combination of monomers with the elimination of small molecules (e.g., water).
• Thermoplastic and Thermosetting Polymers: Thermoplastics can be softened and reshaped upon heating, while thermosets become permanently hard after initial heating and cannot be remolded.
• Structure, Bonding, and Properties: The structure and bonding of polymers determine their properties, such as softening behavior, rigidity, strength, and water solubility.
• Polymer Examples: Examples include poly(ethene) (PE), poly(ethylene terephthalate) (PET), polyamide (nylon), poly(vinyl alcohol) (PVA), poly(vinyl chloride) (PVC), and poly(propene) (PP).
• Recycling: Recycling of plastics is important due to the finite nature of resources and environmental concerns.