scientific terminology
TRANSCRIPT
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Fire and Emergency Services Orientation and Terminology
5th Edition
Chapter 5 — Scientific Terminology
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REVIEW QUESTION
What are the three physical states of matter that fuel can be found in?
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Learning Objective 1
Describe the properties of matter.
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Solid
Liquid
Gas
There are three physical states of matter.
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Density
• Mass per unit of volume of a substance
Specific gravity
• Ratio of mass of given volume of liquid compared with mass of equal volume of water
Vapor density
• Density of gas or vapor in relation to air
Matter can be described using terms derived from its physical properties of mass and volume.
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When a substance remains chemically the same but changes in size, shape, or appearance
Physical Change
When a substance changes from one type of matter into another
Chemical Change
Physical and chemical changes involve an exchange of energy.
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Mass and energy cannot be created or destroyed; reduction in mass of a
fuel results in release of energy - light and heat
More fuel to burn, more potential for greater
amounts of energy being released as heat during a
fire
The more heat that is released, the more
extinguishing agent is needed to control a fire
As fire consumes a fuel, its mass is reduced.
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Explain combustion, the fire tetrahedron, and fire development.
Learning Objective 2
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Combustion is a rapid and self-sustaining reaction that releases energy in the form of heat, light, and byproducts
Modes of combustion –Differentiated based on where the reaction is occurring
Fire is one form of combustion.
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For combustion to occur, four components are necessary.
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REVIEW QUESTION
What are the four elements of the fire tetrahedron?
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Heat
• Potential energy
• Kinetic energy
Temperature
Energy
Ignition
• Piloted
• Autoignition
Heat is a form of energy.
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Chemical heat
energy
Self-heating
Electrical heat
energy
Mechanical heat
energy
There are several sources of heat energy.
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Heat is transmitted in three ways.
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Conduction
(Continued)
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Heat is transmitted in three ways.
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REVIEW QUESTION
How do conduction, convection, and radiation influence the development of fire?
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Solids
Pyrolysis
Surface-to-mass ratio
Liquids
Vaporization
Volatility
Gases
Flammable/ explosive
range
Lower flammable
limit
Upper flammable
limit
Fuel is the material or substance being oxidized or burned in combustion process.
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ExamplesOxygen
Concentrations
Oxidizing agents release oxygen or other oxidizing gases during a chemical reaction.
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REVIEW QUESTION
What chemical reaction do oxidizers support when combined with a fuel?
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The self-sustained chemical reaction involved in flaming combustion is complex.
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A compartment fire is either fuel- or ventilation-controlled.
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There are five stages of a compartment fire.
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REVIEW QUESTION
What are the five major phases of fire?
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Describe special considerations of fire that have particular implications for firefighter safety.
Learning Objective 3
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Unburned fire gases at top of compartment ignite; flames propagate through the hot gas layer or across the ceiling
Distinguished from flashover; involves only fire gases at upper levels of compartment
Will generally precede flashover, but may not always result in flashover
Rollover may occur during the growth stage.
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REVIEW QUESTION
What is the difference between a rollover and a flashover?
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Hottest gases in top layer, cooler gases in lower
layers
Can be disrupted with ventilation
Can be disrupted if water applied directly into the
layer
The thermal layering of gases is the tendency of gases to form layers according to temperature.
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REVIEW QUESTION
What effect does thermal layering have on fire suppression activities?
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A backdraft is an instantaneous explosion or rapid burning of superheated gases.
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SmokeFlames
Products of combustion are the materials produced and released during burning.
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Discuss the four aspects of fire extinguishment theory.
Learning Objective 4
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Fire is extinguished by limiting one or more of the elements in the combustion process.
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REVIEW QUESTION
What are four main fire extinguishment techniques?
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Define the five main classifications of fires.
Learning Objective 5
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Class A
Class B
Class C
Class D
Class K
Each class of fire has its own requirements for extinguishment.
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Summary
• It is crucial that all firefighters understand the science of fire if they are to operate safely and efficiently on the fireground.
• This knowledge is important on the fireground as emergency responders continually evaluate the fire and determine how to attack the fire itself, protect exposures, and ensure the safety of everyone at the scene.
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