explosions and fire Flashcards
What is a fire?
A fire is combustion or burning, where substances combine chemically with oxygen from the air, typically producing light, heat, and smoke.
What is combustion?
Combustion is a rapid combination of oxygen with another substance, accompanied by noticeable heat and light.
What is an exothermic reaction?
An exothermic reaction is a chemical transformation in which heat energy is liberated.
What is heat of combustion?
Heat of combustion is the heat liberated during combustion.
What is a BTU?
BTU (British Thermal Unit) is defined as the quantity of heat required to raise the temperature of 1 pound of water by 1°F at or near its point of maximum density.
What is speed of reaction?
Speed of reaction refers to the liberation of energy through a chemical reaction such as oxidation, where faster molecular movement leads to more collisions and a faster reaction rate.
What are the three requirements to initiate and sustain combustion?
1) A fuel must be present. 2) Oxygen must be available in sufficient quantity. 3) Heat must be applied to initiate combustion and sustain the reaction.
What is heat transfer?
Heat transfer is the process where heat moves from one object to another, such as from a burner to a pot of boiling water.
What is radiation in the context of heat transfer?
Radiation is the transfer of heat energy from a heated surface to a cooler surface by electromagnetic radiation.
What is convection?
Convection is the transfer of heat energy through the movement of molecules within a liquid or gas.
What do fire investigators look for at a fire scene?
Fire investigators examine the fire scene for signs of arson and the point of origin, which indicates the longest burning area.
What is an accelerant?
An accelerant is any material used to start and sustain a fire, such as gasoline or kerosene.
How should evidence from a fire scene be collected and preserved?
Evidence should be collected in an unsealed airtight container to preserve fumes and liquid accelerants for analysis.
What is the headspace technique?
The headspace technique involves poking a hole in the top of a container to extract vapors for analysis through gas chromatography.
What is an explosion?
An explosion is a chemical or mechanical action caused by combustion, accompanied by heat creation and rapid gas expansion.
What are the two types of explosives?
1) Deflagration: a rapid oxidation reaction with a low-intensity pressure wave. 2) Detonation: an extremely rapid oxidation reaction with a violent disruptive effect.
What are low explosives?
Low explosives are black and smokeless powders that decompose quickly when ignited, producing propelling action.
What are high explosives?
High explosives include substances like TNT and dynamite, which detonate almost instantaneously at high speeds.
What are primary and secondary explosives?
Primary explosives are ultra-sensitive to heat, shock, or friction (e.g., TNT). Secondary explosives are insensitive to such factors (e.g., ammonium nitrate).
