Chapter 5 Flashcards
What is a chemical process of oxidation that occurs at a rate fast enough to produce heat and usually light i the form of either a glow or a flame?
Combustion
What is a rapid oxidation process which is a chemical reaction resulting in the evolution of light and heat in varying intensities?
Fire
What is a form of energy characterized by the vibration of molecules and is capable of initiating and supporting chemical changes and changes in state?
Heat
What is the measure of a materials ability to transfer heat energy to other objects?
Temperature
What is a material that will main combustion under specified environmental conditions?
Fuel
What is any material that readily yields oxygen or other oxidizing gas, or that readily reacts to promote or initiate combustion of combustible material?
Oxidizer
What is potential energy?
stored energy possessed by an object that can be released in the future to perform work once released
What is kinetic energy?
the energy possessed by a body because of its motion
What is defined in terms of mechanical energy? It is equal to the energy expanded in applying a force of one newton through a distance of one meter.
Joules
What is an exothermic reaction?
chemical reaction that releases thermal energy or heat
What is an endothermic reaction?
chemical reaction that absorbs thermal energy or heat
What is pyrolysis?
the chemical decomposition of a solid material by heating. Pyrolysis often precedes combustion
What is the physical process that changes a liquid into a gaseous state?
Vaporization
What is ignition?
the process of initiation self-sustained combustion
What are the two forms of ignition?
piloted ignition and autoignition (non piloted)
What is the moment when a mixture of fuel and oxygen encounters an external heat source with sufficient heat or thermal energy to start the combustion reaction?
Piloted ignition
What is the initiation of combustion by heat but without a spark or flame
autoignition
What is the autoignition temperature?
the minimum temperature to which a fuel in the air must be heated in order to start self-sustained combustion. The autoignition temperature of a substance is always higher than its piloted ignition temperature
What is a visible, luminous body of a burning gas emitting radiant energy including light of various colors given off by burning gases or vapors during the combustion process?
Flame
What is the fire triangle?
a model used to explain the three elements necessary for combustion (heat fuel and oxygen)
What is the fire tetrahedron?
model of four elements required for a fire. the four sides represent fuel, heat, oxygen, and self-sustaining chemical chain reaction
What are materials that absorb heat but do not participate actively in the combustion process/
Passive agent
What causes the most fire deaths?
toxic smoke
What is a colorless, odorless, dangerous (both toxic and flammable) gas formed by the incomplete combustion of carbon? It combines with hemoglobin more than 200 times fast than oxygen does
Carbon monoxide
What is a colorless toxic and flammable liquid until it reaches 79 degrees F? Above that temperature it becomes a gas with a faint odor similar to bitter almonds
hydrogen cyanide
What is a colorless odorless heavier than air gas that neither supports combustion nor burns? This is used in portable fire extinguishers as an extinguishing agent to extinguish class B or C fires by smothering or displacing oxygen.
carbon dioxide
What is the kinetic energy associated with the random motions of the molecules of a material or object? This is often used interchangeable with the terms heat and heat energy
Thermal energy
What is the measurement of heat?
Temperature
What form of oxidation is a chemical reaction that increases the temperature of a material without the addition of external heat?
Self-heating
What is the initiation of combustion of a material by an internal chemical or biological reaction that has produced sufficient heat to ignite the material?
Spontaneous ignition
What is the measure of the rate of heat transfer to a surface, expressed in kilowatts?
Heat flux
What is the transfer of heat through or between solids that are in direct contact?
Conduction
What is heat transfer by circulate within a medium such as a gas or a liquid?
Convection
What is heat transfer by way of electromagnetic energy?
Radiation
What are the three mechanisms in which heat can by transferred from one body to another?
conduction, convection, and radiation
What is the tendency or capacity to remain afloat in a liquid or rise in air or gas?
Buoyant
What is the upper layer of hot smoke?
a buoyant later of hot gases and smoke produced by a fire in a compartment
What is the fuel that is being oxidized or burned during combustion?
reducing agent
What is heat of combustion?
total amount of thermal energy that could be generated by the combustion reaction if a fuel were completely burned
What is the Heat Release Rate (HRR)
total amount of heat released per unit time
What is a unit of measure of power or rate or work equal to one joule per second?
Watt
What is the common term used to describe the gaseous state of a fuel that would normally exist as a liquid or solid at standard temperature and pressure?
Vapor
What is the rate at which energy is being transferred over time?
Power
What describes the density of gases in relation to air?
Vapor density
What is the vapor density of air?
1
What is the ratio of the mass of a given volume of liquid compared with the mass of an equal volume of water at the same temperature?
Specific gravity
What is the specific gravity of water?
1
What will flammable liquids do on waters surface? Why?
Float bc the specific gravity is less than one
What is the pressure that vapor’s escaping from a liquid exert?
vapor pressure
What is the measure of the tendency of a substance to evaporate?
vapor pressure
What is the minimum temperature at which a liquid gives off enough vapor’s to form an ignitable mixture with air near the liquids surface?
flash point
What is the temperature at which sufficient vapor’s are being generated to sustain the combustion reaction?
Fire point
What does miscible mean?
materials that are capable of being mixed in all proportions
What are hydrocarbon fuels?
petroleum-based organic compounds that contain only hydrogen and carbon (ex. gasoline, diesel, and fuel oil)
What are polar solvents?
flammable liquids that have an attraction for water (ex. alcohol, ketone, methanol, ethanol)
What is the flammable (explosive) range?
the range between the upper flammable limit and lower flammable limit in which a substance can be ignited
What are free radicals?
molecular fragments that highly reactive
