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70 Cards in this Set

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  • Back
Define "matter"
Matter is anything that occupies space and has mass.
Define "exothermic heat reaction"
A chemical reaction between two or more materials that changes the materials and produces heat, flames, and toxic smoke.
Define "endothermic heat reaction"
Chemical reaction in which a substance absorbs heat energy
Define "combustion"
An exothermic chemical reaction that is a self-sustaining process of rapid oxidation of fuel, producing heat and light
What percentage of our atmosphere is made up of oxygen?
About 21percent
When something burns or "combusts," its potential energy is converted into what kind of energy?
Kinetic energy
What is the key difference between flaming combustion and nonflaming (smoldering) combustion?
In flaming combustion, the fuel is first vaporized, then the resulting gases ignite and produce flame. In smoldering combustion, the oxidation actually occurs right at the surface of the fuel, rather than at the gases resulting from heating the substance.
What is the "fire triangle?"
The fire triangle is a simple, and not totally complete, model for the components required for combustion. It does, however, paint an accurate picture of what's needed for smoldering combustion to occur. It consists of heat, fuel, and oxygen. If you take one of the elements away, the idea is that fire will be forced to die out.
What is the "fire tetrahedron?"
The fire tetrahedron is a more complete model for the components required to create fire, namely flaming combustion. It consists of heat, fuel, oxygen, and a self-sustained chemical chain reaction.
Define "potential energy"
Stored energy possessed by an object that can be released in the future to perform work.
Define "kinetic energy"
The energy possessed by a moving object.
What are the units of measurement used to define heat energy?
The international system expresses heat energy in joules, whereas in the US, many fire services still express heat energy in BTUs (british thermal units)
What are the two most common scales used to measure temperature?
Fahrenheit and celsius
How many BTUs of heat energy does it take to increase the temperature of a pound of water by 1º Fahrenheit?
1 BTU
Define "autoignition temperature"
The temperature at which a material will ignite, even if no external ignition source -- such as a spark or an open flame -- is present.
Define "piloted ignition"
The process through which a mixture of fuel and oxygen encounter an external heat source -- such as a spark or an open flame -- with sufficient heat energy to start the combustion reaction.
The autoignition temperature of a material is always ______ than the material's piloted ignition temperature.
Higher
What are the three types of energy that are most likely to cause the ignition of a material?
Mechanical, chemical, and electrical energy
What is THE most common source of heat in combustion reactions (mechanical, chemical, or electrical energy)?
Chemical heat energy
Define "self-heating"
Also known as spontaneous heating, self-heating is a form of chemical heat energy that occurs when a material increases in temperature without the addition of external heat.
What factors are required in order for spontaneous ignition due to self-heating to occur?
1) The insulation properties of the material immediately surrounding the fuel must be such that the heat cannot dissipate as fast as it is being generated.

2) The rate of heat production must be great enough to raise the temperature of the material to its ignition temperature.

3) The available air supply in and around the material being heated must be adequate to support combustion.
What common material might spontaneously ignite?
Linseed oil-soaked rags
What are the different modes of electrical heating?
1) Resistance heating (when current flows through a conductor -- think of an electric stovetop)

2) Overcurrent or overload (when the current flowing through a conductor exceeds its design limits -- this is basically unintended resistance heating)

3) Arcing (occurs when a conductor is separated, as in a switch or a motor, and under high voltage conditions. Also, static electricity and lightning.)

4) Sparking (sparks are the luminous particles that spatter away from an arc)
What common materials are prone to self-heating, and where are they found?
Charcoal (Found in convenience stores, hardware stores, grocery stores, industrial plants)

Linseed oil-soaked rags (Found in woodworking shops, lumber yards, furniture repair shops, picture frame shops)

Hay, manure, and mulch (Found at farms, feed stores, arenas, feedlots)
Define "mechanical heat energy"
Energy generated by friction or compression. Diesel engines operate on compression and ignite fuel without a spark plug. SCBA tanks heat up when filled too quickly. These are both examples of mechanical heat energy.
The greater the difference of _______ between two bodies, the greater the _______ ____ of heat.
Temperature, transfer rate.
What three mechanisms allow transfer of heat from one body to another?
Conduction, convection, and radiation
Define "conduction"
Physical flow or transfer of heat energy from one body to another through direct contact or an intervening medium from the point where the heat is produced to another location or from a region of high temperature to a region of low temperature.
What material more readily conducts heat -- steel or copper?
copper
What material more readily conducts heat -- concrete or steel?
steel
What's an "insulator?"
A material that slows the conduction of heat transfer from one body to another
What are the best insulators?
Materials made of fine particles or fibers with void spaces between them filled with gas. Air gaps increase insulation, because gases do not conduct heat well.
Define "convection"
Convection is the transfer of heat by the movement of heated fluids or gases, usually in an upward direction
Define "radiation"
Radiation is the transmission or transfer of heat energy from one body to another at a lower temperature through intervening space by electromagnetic waves, such as infrared, radio, or X-rays.
What kind of matter radiates heat energy?
All matter having a temperature above absolute zero (so, everything we know) radiates heat energy.
What mode of heat transfer becomes the dominant mode when a fire grows in size?
Radiation
Which materials radiate and absorb heat more readily -- dark-colored or light-colored materials?
Dark colored materials
Which materials reflect more radiant heat -- highly polished materials or rough materials?
Highly polished materials
Does the temperature difference between two bodies have a great effect on heat transfer through radiation?
Yes!
As the temperature of a heat source increases, the radiant energy increases by a factor of the ____ power.
Fourth --- that means that doubling the temperature increases rate of heat transfer by 16 times.
How fast does radiant heat move?
At the speed of light, since it travels on an electromagnetic wave
What are "passive agents?"
These are materials that absorb heat but do not participate actively in the combustion reaction. Probably the best example for a firefighter to remember is WATER.
Define "reducing agent."
A reducing agent is the fuel that is being oxidized or burned during combustion.
What are the two broadest classifications of fuel?
Organic and inorganic
Organic fuels can be separated into which two categories?
Hydrocarbon-based (petroleum, fuel oil) and cellulose-based (wood and paper)
For flaming combustion to occur, fuel must be in its _____ state.
Gaseous
Why are gaseous fuels so dangerous?
They're dangerous because they're already in the state required for ignition.
What is air's "vapor density?"
1
What common gaseous fuels are less dense than air, and what are their vapor densities?
Methane (.55), Carbon Monoxide (.96)
What happens when fuels less dense than air are released from a container?
The fuels rise
What common gaseous fuel is more dense than air, and what's its vapor density?
Propane (1.52)
Define "specific gravity"
Specific gravity is the weight of a substance compared to the weight of an equal volume of water at a given temperature. Water has a specific gravity of 1. So, fluids with a specific gravity less than 1 are lighter than water, and fluids with a specific gravity greater than 1 are heavier.
In order to burn, liquids must be _______
Vaporized
What pressure does the atmosphere exert at sea level?
14.7 psi
What's "vapor pressure?"
It's the pressure exerted by vapors released by a liquid. In order for a liquid to vaporize, its vapor pressure must overcome the 14.7 psi that the atmosphere exerts on it.
What's an easy way to increase the vapor pressure of a liquid?
Heat it up
Define "flash point"
Temperature at which a liquid gives off sufficient vapors to ignite, but not sustain, piloted ignition and combustion.
Define "fire point"
Temperature at which a liquid fuel produces sufficient vapors to support combustion once the fuel is ignited. The fire point is usually a few degrees above the flash point.
Which is more flammable at normal ambient temperatures -- diesel fuel or gasoline?
Gasoline
What are the flash points for diesel fuel and gasoline?
Gasoline = -36 F
Diesel = 100º F to 150º F
When a flammable liquid's surface area increases, does it become MORE or LESS flammable?
More flammable, because a liquid will give off more vapors the higher its surface area.
When dealing with liquid fuels, what factors must a firefighter always keep in mind?
Flashpoint of liquid
Surface area of liquid
Specific gravity (density) of a liquid
Liquid's ability to mix with water
Why do miscible liquids (liquids that can mix with water) present a challenge to firefighters?
Because they can mix with the water component of firefighting foam and render it useless.
Why do liquid fuels that are lighter than water present a challenge to firefighters?
Water sprayed on these liquids will simply spread them around, increasing their surface area without dousing them, and increasing the size of the fire.
Are gasoline and diesel water soluble?
No
Are ethanol and methanol water soluble?
Yes
Are gasoline, ethanol, and methanol lighter than water?
Yes, they have a lower specific gravity than water
Is diesel fuel lighter than water?
No, it has a slightly higher specific gravity compared to water
What are the flash points of gasoline, diesel, ethanol, and methanol?
Gasoline: -36º F
Methanol: 52º F
Ethanol: 55 ºF
Diesel: 125º F
What are the autoignition temperatures of gasoline, diesel, ethanol, and methanol?
Diesel: 410º F
Ethanol: 689º F
Gasoline: 853ºF
Methanol: 867ºF