Combustion of fuels and the fire triangle

• What is the fire triangle?

  It identifies three things needed for fire.
• What is combustion?

  It is a reaction of fuels with oxygen.
• What percentage of air is oxygen?

  About 21 percent
• What is required for complete combustion?

  A plentiful supply of air is needed.
• What are hydrocarbons?

  Compounds of hydrogen and carbon only.
• What happens to carbon during complete combustion?

  It oxidizes to carbon dioxide.
• What happens to hydrogen during complete combustion?

  It oxidizes to water.
• What is the general equation for complete combustion?

  Hydrocarbon + oxygen → carbon dioxide + water
• What is the significance of calorimetry in combustion?

  • Measures energy released during combustion
  • Helps determine fuel efficiency
• Here is the equation for the complete combustion of methane, used in Bunsen burners:

  methane + oxygen → carbon dioxide + water

  CH4 + 2O2 → CO2 + 2H2O
• Here is the equation for the complete combustion of propane, used in bottled gas:

  propane + oxygen → carbon dioxide + water

  C3H8 + 5O2 → 3CO2 + 4H2O
• Ethanol, a simple alcohol, also combusts to form carbon dioxide and water:

  ethanol + oxygen → carbon dioxide + water

  C2H5OH + 3O2 → 2CO2 + 3H2O
• What does the fire triangle identify?

  Three things required for a fire to burn
• What are the three components of the fire triangle?

  Oxygen, heat, and fuel
• What happens if one component of the fire triangle is removed?

  The fire can no longer burn
• How does a carbon dioxide extinguisher work?

  It pushes oxygen away and replaces it
• What is a fire blanket used for?

  To prevent oxygen from reaching the fire
• Why should doors be closed when evacuating a building?

  To prevent fresh oxygen from entering
• What is a method to remove heat from a fire?

  Using water to absorb the heat
• Why should water not be used on electrical fires?

  It poses a risk of electrical shock
• What happens when water is used on oil fires?

  It makes the fire worse by spreading oil
• How can fire-resistant materials prevent fires?

  They provide inadequate fuel for burning
• What is a firebreak?

  A method to stop forest fires from spreading
• What are the methods to remove components of the fire triangle?

  • Removing Oxygen:
  • Fire blanket
  • CO₂ extinguisher
  • Removing Heat:
  • Water
  • Removing Fuel:
  • Firebreak
• What types of fires correspond to each removal method?

  • Oxygen Removal:
  • Oil fires, chip-pan fires, electrical fires
  • Heat Removal:
  • House fires, wood fires, paper fires
  • Fuel Removal:
  • Forest fires
• The fire triangle

  
• What is the fire triangle?

  It identifies three things needed for fire.
• What does calorimetry measure?

  It measures energy released in reactions.
• What are the steps in a calorimetry experiment?

  1. Measure cold water into a calorimeter.
  2. Record the starting temperature.
  3. Heat water with burning fuel.
  4. Record the final temperature.
  5. Weigh the fuel before and after.
• What is the unit of mass?

  Kilograms (kg) or grams (g).
• Why is fair testing important in experiments?

  It ensures reliable and valid results.
• What variables should be kept constant in a calorimetry experiment?

  • Volume of water used
  • Starting temperature of water
  • Temperature increase
  • Distance of flame from calorimeter
• What is the biggest source of error in calorimetry?

  Unwanted heat loss to surroundings.
• How can heat loss be reduced in calorimetry?

  By insulating the calorimeter and adding a lid.
• How do you calculate energy released in calorimetry?

  • Use the formula:

  Energy given out = mass of water × 4.2 × temperature change

  • Energy measured in joules (J).
• If 3.5 g of fuel heats 50 cm³ of water from 22°C to 71°C, what is the temperature change?

  49°C
• What is the energy given out when heating 50 cm³ of water by 49°C?

  10,290 J
• How do you calculate energy per gram of fuel burned?

  Energy per gram = energy given out ÷ mass of fuel.
• What is the energy released per gram of fuel if 10,290 J is given out from 3.5 g of fuel?

  2,940 J/g
• What is the specific heat capacity of water used in calorimetry calculations?

  • Specific heat capacity = 4.2 J/g°C