Chemistry Academy: Fuels Lecture Notes

Important Definitions

• Fuel: A substance that burns in oxygen to release energy.
  • Important: Cannot create energy; it changes from one form to another.
• Hydrocarbon: A substance containing only hydrogen and carbon atoms.
• Exothermic Reaction: A reaction that releases heat energy (feels hot).
  • Example: Hand warmers.
• Endothermic Reaction: A reaction that absorbs heat energy (feels cold).
  • Example: Ice packs.

Combustion Reactions

• Combustion Reaction: A reaction involving burning in oxygen.
• Complete Combustion:
  • Occurs with plentiful oxygen.
  • Products: Carbon dioxide (CO2) and water (H2O).
  • Common with hydrocarbons and alcohols.
• Incomplete Combustion:
  • Occurs with limited oxygen.
  • Produces: Carbon monoxide (CO), carbon (soot), and water.
  • Carbon monoxide is toxic.
  • Carbon soot is environmentally harmful.

Combustion Examples

• Example 1: Ethane (C2H6) with oxygen forms CO2 and H2O.
• Example 2: Hydrocarbon with sulfur produces SO2, leading to acid rain.

Identifying Products of Combustion

• Any element other than oxygen in products must be in the fuel.
• Experiments can determine products:
  • Condensed colorless liquid indicates water.
  • Cloudy lime water indicates carbon dioxide.

Types of Fuels

Fossil Fuels

• Types: Coal, oil, gas.
• Cons:
  • Produce greenhouse gases (CO2).
  • Finite supply.
• Pro: High energy content.

Alcohols

• Pros:
  • Burn more cleanly; less incomplete combustion.
  • Ethanol is renewable.
• Cons:
  • Takes up land for crops.

Hydrogen

• Pros:
  • Renewable.
  • Non-toxic; only produces water.
• Cons:
  • Expensive production.
  • Risk of explosion.

Fractional Distillation

• Purpose: Separates crude oil into useful fractions.
• Process:
  • Based on boiling points.
  • Higher boiling point substances at bottom, lower at top.
• Fractions and Uses:
  • Gases (top): e.g., Butane (camping gas).
  • Middle fractions: e.g., Kerosene (jet fuel), petrol, diesel.
  • Residue (bottom): Used for tarring roads.

Viscosity

• Smaller molecules: Low viscosity, collected at top.
• Larger molecules: High viscosity, collected at bottom.

Study Tip: Use flashcards for definitions and practice identifying combustion products.