Lecture 13 - Arson 1 Flashcards
give 5 reasons why someone may commit arson
malicious intent
insurance fraud
attempt to harm someone
juvenile disorder
mental health or psychological problems
what might a fire be started with the intention of destroying
evidence of a different crime committed
fingerprint
DNA
fibres
mitochondrial DNA can actually withstand high temperatures
give three common setting of arsons
vehicles
dwelling
theft locations (burglaries)
what can help suggest if the death of a person was pre or post fire
CO in the lungs
what is one of the biggest causes of fires in the UK currently but what is low?
arson
the detection and conviction rates
what was the main aims of setting up the Arson control forum in 2001
how was the achieved
reducing arson related deaths, injuries and damage
by educating more people and giving better education
resources were spent in a targeted manner to cause maximum impact
the money spent looks like a lot but the money this save the UK on damage costs was massive
what 4 research areas did the Arson control forum dive into in aim to reduce arson incidents
the motivation of arsonists
links between arson and vehicle crime
social exclusion and fire risk
why arson prosecution fail
what has the arson control forum now been rebranded as
the Arson Prevention Forum
since 2013
recently has there been an increase or decrease in the amount of arson
increase
the only benefit to this is giving work to forensic investigators
in what 3 ways can a fire be considered accidental but still hold legal liability in a criminal proceeding
1 - infringement of safety regulations and legislation = unlicensed storage or unsuitable storage
2 - neglect and failure to employ duty of care = not doing safety checks properly
3 - fire caused as consequence of committing another crime = illegal bypass of gas metres
why is it beneficial to just put the mitigation procedures in place
the cost to implement them is much lower than the cost after a fire has occurred
what is a combustion
the process of burning
a chemical change (particularly oxidation) with the production of light and heat
what is a fire
a rapid, persistent, chemical change that releases heat and light and is accompanied by flame - particularly in the exothermic oxidation of a combustible substance
a fire is a continuous series of exothermic, oxidative reactions that involve the fuels present
what is the key difference between a fire and a combustion
the presence of a flame
a fire is a flaming combustion
what are the physics and chemistry definitions of a flame
1 = the zone of burning gases and fine suspended matter associated with rapid combustion - a hot glowing mass of burning vapour. the condition of active, blazing combustion
2 = a region in which chemical interaction between gases occurs, accompanied by the evolution of heat and light
what are the 3 components of the fire triangle
heat
oxygen
fuel
how much heat is needed for a combustion to occur
enough to overcome the intitial activation energy
how can a fire be prevented or extinguished
by removing one or more of the three components of the fire triangle
what is required for a fire to start
a initial ignition soruce or spark
what is needed for a fire to maintain and persist
a chemical chain reaction
what type of process is a combustion - oxidation or reduction
oxidation
what are the products of a complete combustion of a hydrocarbon fuel
carbon dioxide (gas) and water (liquid)
assumption is made that complete combustion occurs
is an oxidation and exo or endothermic process
exothermic = heat energy is liberated
what is the heat liberated in a combustion called
the heat of combustion or enthalpy of combustion at a constant pressure
what conditions does the standard enthalpy of combustion refer to
standard conditions = temp 298K, 1atm pressure
what is the oxidation number of a pure element
0
what is the oxidation number of a charged species
its charge
what is the oxidation number of the alkali metals
+1
what is the oxidation number of group 2 metals (alkaline earth metals)
+2
what is the oxidation number of a halogens
-1
what is the oxidation number of hydrogen
+1 unless in a metal hydride = MHx where it is -1
what is the oxidation number of oxygen
-2 unless in a peroxide O-O = -1
what happens in a combustion where there is a limited oxygen supply
incomplete combustion occurs and carbon monoxide is produced = toxic and can undergo further combustion to CO2
what is an impurity found in many fuels
sulphur
what is the complete combustion product of sulphur
SO3 but SO2 is more commonly seen as the complete combustion is a very slow process