The Chemistry of Fire

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The Chemistry of Fire
2010-12-14 22:01:13
BU Forensic Chemistry

Arson and Ignitable Liquids
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  1. Characteristics of Distillates MS
    • Bell shaped curves
    • equal peak separation
    • least refined of all petroleum products
  2. What are the 3 categories of petroleum distillates?
    • light
    • medium
    • heavy
  3. Characteristics of Gasoline MS
    • high aromatics content
    • low abundance of alkanes
    • xylene trios w/ 1:2:1 ratio

    Neat: wider range covered, with more intense peaks, closer to start of x axis

    25% evaporated: more narrow range and shorter peaks than neat, close to start

    99% evaporated: less intense peaks, towards middle of x axis
  4. MS characteristics of Isoparaffinic products
    • distinct, narrow range products
    • abundant alkanes w/o n-alkanes pattern

    narrow and intense peaks squash together
  5. MS characteristics of Aromatic products
    • distinct, narrow range compounds
    • more narrow than isoparaffinic products
  6. MS characteristics of N-Alkane products
    • simple patterns
    • notable lack of everything but straight chain alkanes
    • cleaner and less complicated than distillates
    • only a handful of peaks
  7. MS characteristics of Naphthenic/ Paraffinic products
    • cyclo and iso alkanes (rings and branched alkanes)
    • gaussian distribution
    • unresolved baseline
  8. What are the four conditions required for a fire?
    • fuel
    • heat
    • oxidizing agent
    • uninhibited chemical chain reaction
  9. Flash point
    temperature at which sufficient vapors are given off to form an ignitable mixture with air
  10. Fire point
    temperature at which burning is self-sustained after the removal of an ignition source
  11. Ignition temperature
    temperature at which a fuel must be heated before it spontaneously combusts
  12. What are the stages of fire?
    • ignition
    • growth
    • flashover
    • fully developed
    • decay
  13. ______ is the process of all the materials in a room reaching their ignition temperature at the same time
  14. _____ is the chemical breakdown of larger molecules to smaller molecules in the absence of oxygen
  15. What are the three methods of heat transfer?
    • conduction
    • convection
    • radiation
  16. _______ is the passage of heat from one material to another by direct contact
  17. ______ is the transfer of heat through a gas or a liquid
  18. ______ is the transfer of heat through electromagnetic waves
  19. What are 3 factors that can affect the fire and its spread?
    • presence/absence of suppression
    • ventilation
    • fuel load
  20. What is an accelerant?
    any fuel or oxidizing used to initiate a fire or increase the rate of growth or speed the spread of fire
  21. T/F: Alkylation is a process opposite that of cracking.
  22. T/F: High octane gasoline is produced via cracking.
    False! It is produced via alkylation
  23. Alkylation and catalytic cracking are both ___-thermic.