AQA Chemistry Paper 2 Revision Notes

Topics Covered

• Rates of Reaction
• Organic Chemistry
• Analysis
• Atmosphere Chemistry
• Resources

Rates of Reaction

• Rate Definition: Change in quantity (reactant used/product formed) divided by time.
• Experiments:
  • Hydrochloric acid and sodium thiosulfate: reaction turns solution cloudy, stop timer when cross on paper is no longer visible.
  • Measure gas volume with a gas syringe connected to reaction vessel.
• Graph Analysis:
  • Plot quantity vs time.
  • Draw tangent to find rate at any point.
• Increasing Reaction Rate:
  • Increase concentration, pressure, surface area.
  • Increase temperature (particles move faster, collide with more energy).
  • Add catalyst (lowers activation energy).

Reversible Reactions

• Equilibrium in a closed system: Forward and reverse reactions occur at same rate.
• Le Chatelier's Principle: System adjusts to counteract changes (e.g., pressure, concentration, temperature).
• Temperature and Reaction: Higher temperature favors endothermic; lower favors exothermic.

Organic Chemistry

• Crude Oil and Hydrocarbons:
  • Made from plankton remains; mixture of hydrocarbons, mostly alkanes.
  • Separated via fractional distillation.
• Fractional Distillation:
  • Separates based on boiling points; higher in column = shorter chains.
• Alkanes vs Alkenes:
  • Alkanes: Saturated, single bonds.
  • Alkenes: Unsaturated, double bonds.
• Testing for Alkenes: Bromine water test (turns colorless).
• Cracking: Breaks long alkanes into shorter alkanes and alkenes.
  • Catalytic and steam cracking.
• Polymers:
  • Made from alkenes through addition polymerization.
  • Condensation polymerization produces polymers and small molecules like water.
  • Natural polymers include DNA, starch, proteins.

Chemical Analysis

• Purity Testing: Melting/boiling point.
• Chromatography: Separates substances; RF value calculation.
• Flame Tests: Identify metal ions based on flame color.
• Precipitation Tests: Identify ions in solutions, e.g., chlorides, sulfates.
• Instrumental Methods: Accurate and fast, e.g., flame emission spectroscopy.

Atmospheric Chemistry

• Earth's Atmosphere Evolution: Early atmosphere rich in CO2, changed by photosynthesis.
• Greenhouse Gases: CO2, methane absorb radiation, warming earth.
• Carbon Footprint: CO2 emissions from human activities.
• Pollutants: Carbon monoxide, sulfur dioxide, nitrogen oxides.

Resources

• Sustainability: Using resources without compromising future needs.
• Water Treatment: Making water potable through filtration and sterilization.
• Metal Extraction: Phytomining, bioleaching.
• Life Cycle Assessment: Evaluating environmental impact of products.
• Recycling: Reduces environmental impact, e.g., glass, metal recycling.
• Corrosion: Metal deterioration; prevent with coatings.
• Alloys: Mixtures of metals for improved properties.
• Glass and Ceramics: Types and uses.
• Composites: Combination of materials for enhanced properties.
• Harbor Process: Produces ammonia for fertilizers; balance between yield and rate.
• Fertilizers: Contain nitrogen, phosphorus, potassium.

Study Tips

• Use diagrams to visualize processes, especially for chemical reactions and distillation.
• Practice drawing and interpreting graphs.
• Memorize key reactions and tests for quick recall during exams.

Note: For any complex concepts or unfamiliar terms, refer to your textbook or additional resources for detailed explanations and examples.