Fire and Emergency Services Orientation and Terminology

5th Edition

Chapter 5 — Scientific Terminology

REVIEW QUESTION

What are the three physical states of matter that fuel can be found in?

5–1

Learning Objective 1

Describe the properties of matter.

5–2

Solid

Liquid

Gas

There are three physical states of matter.

5–3

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.

5–4

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.

5–5

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.

5–6

Explain combustion, the fire tetrahedron, and fire development.

Learning Objective 2

5–7

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.

5–9

REVIEW QUESTION

What are the four elements of the fire tetrahedron?

5–10

Heat

• Potential energy

• Kinetic energy

Temperature

Energy

Ignition

• Piloted

• Autoignition

Heat is a form of energy.

5–11

Chemical heat

energy

Self-heating

Electrical heat

energy

Mechanical heat

energy

There are several sources of heat energy.

5–12

Heat is transmitted in three ways.

5–13

Conduction

(Continued)

Heat is transmitted in three ways.

5–14

REVIEW QUESTION

How do conduction, convection, and radiation influence the development of fire?

5–15

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.

5–16

ExamplesOxygen

Concentrations

Oxidizing agents release oxygen or other oxidizing gases during a chemical reaction.

5–17

REVIEW QUESTION

What chemical reaction do oxidizers support when combined with a fuel?

5–18

The self-sustained chemical reaction involved in flaming combustion is complex.

5–19

A compartment fire is either fuel- or ventilation-controlled.

5–20

There are five stages of a compartment fire.

5–21

REVIEW QUESTION

What are the five major phases of fire?

5–22

Describe special considerations of fire that have particular implications for firefighter safety.

Learning Objective 3

5–23

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.

5–24

REVIEW QUESTION

What is the difference between a rollover and a flashover?

5–25

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.

5–26

REVIEW QUESTION

What effect does thermal layering have on fire suppression activities?

5–27

A backdraft is an instantaneous explosion or rapid burning of superheated gases.

5–28

SmokeFlames

Products of combustion are the materials produced and released during burning.

5–29

Discuss the four aspects of fire extinguishment theory.

Learning Objective 4

5–30

Fire is extinguished by limiting one or more of the elements in the combustion process.

5–31

REVIEW QUESTION

What are four main fire extinguishment techniques?

5–32

Define the five main classifications of fires.

Learning Objective 5

5–33

Class A

Class B

Class C

Class D

Class K

Each class of fire has its own requirements for extinguishment.

5–34

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.

5–35