Ch. 10 Arson Flashcards
accelerant
any material that is used to start a fire, but usually an ignitable liquid
activation energy
the amount of energy that must be applied to reactants to overcome the energy barrier to their reaction
alkane
a hydrocarbon containing only carbon-carbon single bonds
backdrift
an event in which an oxygen-starved fire suddenly receives oxygen
- sudden rush of oxygen causes the smoldering materials present to reignite at the same time
- causes an explosion
combustible liquids
liquids w/ flash points ≥ 100˚F (38˚C)
(ie) kerosene & fuel oil
endothermic reaction
a chemical reaction in which heat is absorbed
energy
the ability to do work
- forms: heat, chemical, electrical, or mechanical
exothermic reaction
a chemical process that releases heat to the surroudnings
flammable liquids
liquids w/ flash points ≤ 100˚F (38˚C)
flammable range
the range of vapor concentrations in air that is capable of burning
flashover
the temperature at which a fire begins unrestrained growth
- can cause complete destruction
flash point
the minimum temperature at which a liquid fuel will produce enough vapor to burn
fractional distillation
the separation of components of petroleum by boiling followed by condensation into fractions w/ similar boiling ranges
- small molecules w/ low bp emerge 1st
- large molecules w/ high bp emerge 2nd
gas chromatography (GC)
a technology used to separate complex mixtures of hydrocarbons, alcohols, ethers & ketones
gas chromatography-mass spectrometry (GC-MS)
use of a gas chromatograph (separates components of a mixture) in conjunction w/ a mass spectrometer (identifies each component by measuring its mass)
headspace
the space above fire debris that has been stored in a sealed container
hydrocarbon
a chemical that contains only two elements: carbon & hydrogen
incipient stage
the growth phase of a fire, which begins at ignition
kerosene
a petroleum fraction that boils at temperatures btwn 100˚F (149˚C) and 550˚F (288˚C)
- used in space heaters, cook stoves & wick lamps
lower explosive limit (LEL)
the lowest concentration of vapor in air that will burn
oxidation
a chemical reaction in which oxygen is combined w/ other substances
pyrolysis
the decomposition of a substance by application of heat
structural isomers
organic compounds that have the same formula but different molecular structures
upper explosive limit (UEL)
the highest concentration of vapor in air that will burn
_________ is the leading cause of arson.
drugs
Oxidation is a chemical reaction between a substance and _________.
oxygen
_______ reactions produce heat.
exothermic
_______ reactions absorb heat.
endothermic
The rate of chemical reaction is the ________ at which reactions are converted into products.
energy
The minimum amount of energy that a reactant molecule must possess to react is called the ________.
activation energy
The three factors that affect the rate of a chemical reaction are _________, ________, and _________.
1) temperature
2) concentration of reactants
3) presence of catalysts
A fuel will produce a flame only when a sufficient number of fuel molecules are in the ________ state.
gaseous
The _______ is the minimum temperature at which a liquid fuel will produce enough vapor to burn.
flash point
Liquids with flash points of 100˚F (38˚C) or higher are known as _______ liquids.
combustible
Liquids with flash points of 100˚F (38˚C) or lower are known as _______ liquids.
flammable
The breakdown of solids by heat is called ________.
pyrolysis
Yellow flames indicate ________ combustion.
incomplete
________ is a term that describes combustion at a surface that occurs without flames.
combustion
The concentration of gaseous fuel that will support combustion is called the _________.
flammable range
The lowest concentration of gaseous fuel that will support combustion is called the _______.
lower explosive limit (LEL)
A vapor density that is ________ (greater/less) than 1 means the vapor is lighter than air.
less
The rate of chemical oxidation (burning) ______ for every 50˚F (10˚C) rise in the temperature.
doubles
The first stage of a fire is called the ________ stage.
incipient
The second stage of a fire is called the ________ stage.
growth
______ occurs when there is spontaneous combustion of all fuels in a room.
flashover
If oxygen suddenly comes in contact with smoldering material, an explosive reaction can take place that is commonly called ________.
backdrift
Heating wood causes it to decompose by releasing gases and leaving a solid residue called _________.
ash
A common fire pattern has a distinctive ______ shape.
V
In determining the origin of a fire, the _______ theory helps identify the source of the fire.
backwards
Hydrocarbons that contain only single bonds are called ________.
alkanes
Crude petroleum is separated by _______ ________ in the refinery.
fractional distillation
Accelerant residue in fire debris is removed by one of two techniques ________ or ______.
passive headspace diffusion (charcoal sampling)
solid-phase microextraction
In gas chromatography, the sample is usually introduced into the GC instrument by a(n) _________.
injector
Generally, the component of the sample with the _______ boiling point comes out last.
highest
Individual components of a sample produce symmetrically shaped GC peaks, and the ________ is proportional to the concentration of that component.
area under each peak
Each component of a sample has a unique GC _______ ________.
fingerprint
