rapid combination of oxygen with another substance, accompanied by the production off noticeable heat and light
a chemical transformation in which heat energy is absorbed from the surroundings
the entire range of possible gas of vapor fuel concentrations in air that are capable of burning
combustion on the surface of a solid fuel in the absence of heat high enough to pyrolyze the fuel
a fire caused by a natural heat-producing process in the presence if sufficient air and fuel
What is combustion? why is rusting not accompanied by it?
rapid combination of oxygen with another substance, accompanied by the production off noticeable heat and light; rusting is not accompanied because iron combines with oxygen too slowly to permit combustion
in what physical state must a fuel exist in order to produce combustion when it reacts with oxygen? Why must it be in this state?
gaseous' molecules collide frequently with one another enough to support a fire
what is pyrolysis? how does it produce fire?
the decomposition of solid organic matter by heat; the gaseous products of pyrolysis combine with oxygen to produce fire
define and give two examples of glowing combustion
combustion on the surface of a solid fuel in the absence of heat high enough to pyrolyze the fuel ; cigarette and red glow of hot charcoal
what three requirements must be satisfied to initiate and sustain combustion
1. fuel must be present
2. oxygen must be available in sufficient quantity to combine with the fuel
3. heat must be applied to initiate the combustion and sufficient heat must be generated to sustain the reaction
as a fire progresses toward what region does the heat created by combustion tend to move?
from a high temperature region to a low temperature region
list and define three mechanisms of heat transfer
conduction- movement of heat through a solid object
radiation- transfer of heat from a heated surface to a cooler surface by electromagnetic radiation
convection- transfer of heat energy by movement of molecules within a liquid or gas
list three common signs of arson at a fire scene
1.presence of containers capable of holding an accelerant
2. discovery of a lighting device
3. irregular shaped burn patterns on the floor and ground
name three reasons why arson investigators must work quickly to collect evidence at a fire scene
1. accelerant residue evaporate within days/hours
2. safety- clean up needs to take place quickly
3. accelerants can quickly be degraded by bacterial action
what are streamers? what does evidence of their presence suggest?
they are accelerants like gas/paper that help fire spread rapidly. they suggest arson
why should fire evidence be packaged in airtight containers?
so possible residues are not lost through evaporation
what instrument do most criminalists consider the most sensitive and reliable for detection and characterizing flammable residue
what is headspace? how it is recovered?
vapors containing residue in the debris of a fire is heated and driven off and trapped in an airtight container's enclosed airspace ' its removed with a syringe
Burning methane for the purpose of heating water to produce stream in order to drive a turbine is an example of converting ___ energy to ____ energy?
chemical to mechanical
The quantity of heat evolved from a chemical reaction arises out of the ___ and ___ of chemical bonds
breaking and formation
Molecules must ____ energy to break their bonds and ____ energy when their bonds are reformed
absorb; give off
____ containers must be used to package all materials suspected of containing hydrocarbon residues
the identity of a volatile petroleum residue is determined by the ____ of its gas chromatograph