GCSE Chemistry Notes
GCSE Chemistry Notes
Unit 2 Overview
Subject: Chemical Bonding, Application of Chemical Reactions, Organic Chemistry
Exam Duration: 1 hour 45 minutes (45% of qualification)
Topics Included:
2.1 Bonding, structure, and properties
2.2 Acids, bases, and salts
2.3 Metals and their extraction
2.4 Chemical reactions and energy
2.5 Crude oil, fuels, and organic chemistry
2.6 Reversible reactions, industrial processes, and important chemicals
2.1 Bonding, Structure, and Properties
Key Concepts
Properties of Compounds: Metals, ionic compounds, simple molecular covalent substances, giant covalent substances.
Electronic Structure and Bonding:
Ionic Bonding: Transfer of electrons represented via dot and cross diagrams.
Covalent Bonds: Sharing of electrons in molecules illustrated with dot and cross diagrams.
Intermolecular Forces: Discussing simple molecular structures.
Metal Properties
High Melting/Boiling Points: Due to strong metallic bonds; they conduct heat/electricity (electrons are free to move).
Properties of Specific Carbons:
Diamond: Very hard (4 covalent bonds per carbon).
Graphite: Soft and conducts electricity; atoms arranged in layers with delocalised electrons.
Carbon Nanotubes: High strength, electricity conduction; used in electronics and materials.
Fullerenes: Spherical structures (e.g., Buckminsterfullerene), can encapsulate other molecules.
Nanoscience
Use of nano-scale silver and titanium dioxide: Antibacterial and UV absorption properties, risks concerning long-term effects on health and environment.
2.2 Acids, Bases, and Salts
Definitions & Reactions
pH Scale: Identifying substances as acidic, alkaline, or neutral.
Acids produce H+ ions; alkalies yield OH- ions.
Reactions
Neutralization: H+(aq) + OH^-(aq) → H₂O(l)
Metal Reactions: Includes simple reactions between dilute acids and various metals.
Identifying Functional Groups: Test methods such as adding barium chloride to detect sulfate ions and hydrochloric acid for carbonates.
Fertiliser Production
Produced through neutralization of ammonia with acids (e.g., ammonium sulfate and ammonium nitrate).
Eutrophication: Impact of fertilizer runoff on water bodies.
2.3 Metals and Their Extraction
Extraction Methods
Metals found in ores; extraction depends on metal reactivity (e.g., electrolysis for reactive metals).
Blast Furnace for Iron: Combines iron ore with coke and limestone to produce iron; reactions include:
Iron Oxide reduction by carbon monoxide: Fe₂O₃ + 3CO → 2Fe + 3CO₂.
Haber Process: Ammonia production via the reaction of nitrogen and hydrogen.
Environmental Impacts
Discussion on metal mining, habitat destruction, metal waste, and the economic factors influencing extraction processes.
2.4 Chemical Reactions and Energy
Reaction Types
Exothermic Reactions: Produce heat (e.g., combustion).
Endothermic Reactions: Absorb heat.
Activation Energy
Is the minimum energy required for a reaction to occur, often visualized through energy profile diagrams, illustrating energy changes between reactants and products.
Bond Energies
Using bond energy values to calculate overall reaction energy changes to identify whether a reaction is exothermic or endothermic.
2.5 Crude Oil, Fuels, and Organic Chemistry
Overview of Crude Oil
Composed of a mixture of hydrocarbons formed via the decomposition of marine organisms over millions of years.
Fractional Distillation: Separation process based on boiling points: gasoline, kerosene, diesel, etc.
Hydrocarbon Properties
Trends in physical properties (e.g., viscosity, ignition quality, color) as chain length increases.
Hydrogen as Fuel
Hydrogen combustion produces only water; advantages include environmental cleanliness, while disadvantages involve production energy costs and storage concerns.
2.6 Reversible Reactions, Industrial Processes, and Important Chemicals
Important Processes
Haber Process for Ammonia: Industrial production method involving reversible reactions.
Contact Process for Sulfuric Acid: Production through oxidizing sulfur dioxide to sulfur trioxide.
Fertiliser Production
Discusses benefits and environmental impacts of nitrogen-rich fertilizers, e.g., nitrogen runoff leading to eutrophication of aquatic ecosystems.
Chemical Tests
Methods for detecting various ions, conducting flame tests, and colorimetric tests for organic compounds.
Chemical Tests
Tests for Gases and Ions
Hydrogen: Squeaky pop test.
Oxygen: Relights glowing splint.
Ammonia: Turns damp litmus blue.
Sulfate Test: Precipitate formed when barium chloride reacts with a sulfate ion.
Summary of Key Reactions and Their Equations
Key Chemical Equations
Ammonia production from nitrogen and hydrogen:
N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
Synthesis of sulfuric acid via Contact Process:
S + O₂ → SO₂
2SO₂ + O₂ ⇌ 2SO₃
SO₃ + H₂O → H₂SO₄