Extinguishing Properties of Water
Course
Firefighter I
Unit VII
Water Supply
Essential
Question
Why is water
used as the
primary
extinguishing
agent in the fire
service?
TEKS
§130.299(c)
(9)(A)(B)(C)
Prior Student
Learning
How heat
transfer, fire
triangle, and fire
tetrahedron
relate to the
flaming and
smoldering
modes of
combustion
Estimated Time
2 hours
Rationale
Understanding the extinguishing characteristics of water, and the efficiency in
which it extinguishers fire, is important for understanding strategies in which it
will be applied. The primary way in which water extinguishes fire is by cooling
(absorbing heat from the fire), but water can also be used to smother a fire by
diluting or excluding oxygen. This happens as water vaporizes and is
converted to steam.
Objectives
The student will be able to:
1. Describe the physical characteristics of water
2. Explain the Law of Specific Heat, the Law of Latent Heat of Vaporization,
and the Law of Heat Flow
3. Compare the advantages and disadvantages of water as an
extinguishing agent
Engage
Engage the students in discussion relating the extinguishing characteristics of
water as they apply to the tactical and strategic decisions involved in fighting
fires. Decisions regarding direct aggressive interior attack or using water to
protect exposures are often made in relation to water’s availability, the stage of
the fire, and the safety of fire personnel and civilians. How and when water is
used as an agent can have a positive or negative effect on the outcome at an
emergency scene. Use the Discussion Rubric to assess the students’
understanding.
Key Points
I. Physical Characteristics of Water
A. Water exists in one of three physical states:
1. Solid – as ice. Water freezes at 32°F or 0°C
2. Liquid – between the temperatures of 32°F and 212°F (0–100°C)
3. Gas – as invisible water vapor. Water vaporizes at 212°F or 100°C
B. Water weighs 8.33 pounds per gallon
C. Water expands to 1700 times its original volume when converted to
steam at 212°F
II. The Law of Specific Heat
A. Specific Heat is the measurement of the heat-absorbing capacity of a
substance. Water is noncombustible and can also absorb large
amounts of heat
B. The ratio of the amount of heat required to raise the temperature of a
unit of mass of a substance by one unit of temperature to the amount of
heat required to raise the temperature of a similar mass of a reference
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material, usually water, by the same amount
C. In SI, specific heat is the temperature required to raise the temperature
of 1 gram of water 1 degree C (1 calorie)
D. In the customary system, specific heat is the temperature required to
raise the temperature or 1 pound of water 1 degree F (1 BTU/British
Thermal Unit)
E. A BTU is the standard measurement used to show the amount of
energy that a fuel has as well as the amount of output of any heatgenerating device
III. The Law of Latent Heat of Vaporization
A. Latent heat is the amount of heat energy absorbed or released during a
change of state (solid<->liquid<->gas). The energy that is required to
change a substance from a liquid state to a gaseous state is called
Latent Heat of Vaporization
B. Complete vaporization does not occur immediately upon water reaching
its boiling point at 212°F. The temperature must remain constant until
the entire volume of water is converted
C. The smaller the water droplet or particle, and the larger the number of
them (the greater the surface area), the more rapidly the conversion to
steam will occur
D. Water will expand to 1700 times its original volume upon complete
conversion to steam
E. Specific heat is relative to the Law of Latent Heat of Vaporization
because, as water is used to cool the fire, it absorbs energy (BTUs) in
the process
F. Through this heat absorption, the fire is effectively controlled by cooling
the fuel below its ignition temperature, and making an interior fire attack
possible because there is now a tenable work environment
G. Converting water to steam is the means by which an indirect fire attack
is conducted
H. The Law of Latent Heat of Vaporization is important in firefighting
because the temperature of the water is not increased beyond 212°F
during the absorption of 970 BTU’s for every pound of water converted
to steam
IV. Law of Heat Flow
A. Heat flows from hot to cold. The 2nd law of thermodynamics – heat
flows spontaneously from a hot to a cold body
1. For heat to be transferred from one body to another, the two bodies
must be at different temperatures
2. Heat moves from warm or hot objects to cooler objects
3. The rate at which the heat transfer occurs is dependent upon the
temperature difference between the two objects, and the
conductivity of the materials involved. The greater the difference,
the greater the transfer rate over time
V. Advantages of Water as an Extinguishing Agent
A. Water is readily available, and is not cost prohibitive (it is considered to
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be inexpensive)
B. Water has greater heat absorbing capability (higher specific heat) than
most all other common extinguishing agents
C. Water takes a relatively large amount of heat to completely convert to
steam (high latent heat of vaporization)
D. Water can be used in many different forms or ways:
1. As a solid stream
2. As a broken stream
3. From a fog nozzle as a
a) Straight stream
b) Narrow pattern fog stream
c) Wide pattern fog stream
VI. Disadvantages of Water as an Extinguishing Agent
A. Water has high surface tension
B. Water can react readily with some materials like combustible metals
C. Water allows radiant heat to pass through it
D. Water freezes at 32°F
E. Water readily conducts electricity
Activities
1. After discussing the extinguishing properties of water, have the students
read about Fire Streams, then complete the Extinguishing Properties of
Water Handout. Students may work individually, as partners, or in small
groups. Use the Extinguishing Properties of Water Handout Key
2. Have the students review the Extinguishing Properties of Water Checklist.
Upon completion of the skills review, students are to complete the skills
under the supervision of an instructor. Use the Extinguishing Properties of
Water Checklist for assessment.
Assessments
Extinguishing Properties of Water Quiz and Key
Extinguishing Properties of Water Handout Key
Extinguishing Properties of Water Checklist
Discussion Rubric
Materials
Extinguishing Properties of Water computer-based presentation
Extinguishing Properties of Water Handout
Fire service equipment as needed for skills demonstration
Resources
0135151112, Essentials of Firefighting (5thEdition), International Fire Service
Training Association (IFSTA)
Accommodations for Learning Differences
For reinforcement, students will participate in peer teaching (mentoring), team
learning, guided research, and note-taking (web-based). Students may also
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keep journals for key words and definitions.
For enrichment, students will participate in hose deployment and fire stream
selection during manipulative training.
Instruction can be differentiated by use of an oral exam, skill demonstration, or
written testing. When a student has met the minimum standard to be
considered competent in the didactic phase of instruction, as well as the tactile
learning phase, it should be recorded.
State Educational Standards
Texas Essential Knowledge and Skills for Career and Technical Education
§130.299 Firefighter I (One to Two Credits).
(9) The student describes the characteristics of water as it relates to fire
extinguishing potential. The student is expected to:
(A) describe the physical characteristics of water;
(B) explain the Law of Specific Heat, the Law of Latent Heat, and the Law of
Heat Flow; and
(C) compare the advantages and disadvantages of water as an
extinguishing agent.
College And Career Readiness Standards
IV. Listening
B. Listen effectively in informal and formal situations
1. Listen critically and respond appropriately to presentations.
2. Listen actively and effectively in one-on-one situations
3. Listen actively and effectively in group discussions.
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Name: ___________________________
Date: ____________________
Extinguishing Properties of Water Handout
1. Describe the physical characteristics of water.
2. Explain the Law of Specific Heat.
3. Explain the Law of Latent Heat.
4. Explain the Law of Heat Flow.
5. Compare the advantages and disadvantages of water as an extinguishing agent. Discuss at least
three of each.
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Extinguishing Properties of Water Handout Key
Because the students are to use their own words the correct answers will vary.
6. Describe the physical characteristics of water.
 Water exists in one of three physical states:
o Solid – water freezes as ice at 32°F or 0°C
o Liquid – between the temperatures of 32°F and 212°F (0–100°C)
o Gas – (invisible water vapor) vaporizes at 212°F or 100°C
 Water weighs 8.33 pounds per gallon and expands to 1700 times its original volume when
converted to steam at 212°F
7. Explain the Law of Specific Heat.
 The measurement of the heat absorbing capacity of a substance
8. Explain the Law of Latent Heat.
 Latent heat – the amount of heat energy absorbed or released during a change of state
(solid<->liquid<->gas)
 Latent Heat of Vaporization – the energy that is required to change a substance from a liquid
to a gaseous state.
9. Explain the Law of Heat Flow.
 The 2nd law of thermodynamics – heat flows spontaneously from a hot to a cold body
 For heat to be transferred, the two bodies must be at different temperatures
 Heat moves from warm or hot objects to cooler objects
 The rate at which the heat transfer occurs is dependent on the
o temperature difference between the two objects
o conductivity of the materials involved
o greater the difference, the greater the transfer rate
10. Compare the advantages and disadvantages of water as an extinguishing agent. Discuss at least
three of each.
Advantages
 Readily available and considered inexpensive
 Has a greater heat absorbing capability (higher specific heat) than most common
extinguishing agents
 Takes a relatively large amount of heat to completely convert to steam (high latent heat of
vaporization)
 Used in many different forms or ways:
o As a solid stream
o As a broken stream
o From a fog nozzle as a straight stream, narrow pattern fog stream, or wide pattern fog
stream
Disadvantages
 Has high surface tension
 Can react readily with some materials like combustible metals
 Allows radiant heat to pass through it
 Freezes at 32° F or 0° C
 Conducts electricity readily
 Class D fires involve combustible metals that water readily reacts with if used as an
extinguishing agent
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Name: ___________________________
Date: ____________________
The Extinguishing Properties of Water Quiz
1. ____ How much does a gallon of water weigh?
a. 8.33 pounds
b. 9.55 pounds
c. 3.88 pounds
d. 5.99 pounds
2. ____ Water expands to ______ times its original volume when converted to steam.
a. 1200
b. 1300
c. 1500
d. 1700
3. ____ Water is in a solid state at ___ degrees C and below.
a. 100
b. 0
c. 212
d. 32
4. ____ Water is in a liquid state between ____ and ____ degrees F.
a. 0, 100
b. 32, 100
c. 32, 212
d. 0, 212
5. ____ Water vaporizes at
a. 212 degrees F
b. 100 degrees C
c. Both a and b are correct
d. Neither a or b are correct
6. ____ Which of the following statements is incorrect?
a. Water is noncombustible
b. Water absorbs relatively insignificant amounts of heat as it is converted to
steam
c. Water absorbs relatively large amounts of heat
d. Complete vaporization does not occur immediately upon water reaching its
boiling point
7. ____ The smaller the water droplet, or particle, and the larger the number of them (the
greater the surface area), the more rapidly the conversion to steam will occur.
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a. True
b. False
8. ____ A pound of water absorbs ____ BTUs as it is converted to steam.
a. 8080
b. 690
c. 869
d. 970
9. ____ Water exists in one of two physical states: liquid or solid (ice).
a. True
b. False
10. ____ All of the following are considered advantages of water as en extinguishing
agent except
a. Water is readily available and is not cost prohibitive
b. Water takes a relatively large amount of heat to completely convert to steam
c. Water allows radiant heat to pass through it
d. Water can be used in many different forms or ways
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Extinguishing Properties of Water Quiz Key
1. A
2. B
3. D
4. C
5. C
6. B
7. A
8. D
9. B
10. C
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Name:_________________________
Date:___________________________
The Extinguishing Properties of Water Checklist
Directions: Follow the steps below for all four of the objectives.
Objectives: Under the supervision of the instructor properly operate
1) a solid-stream nozzle
2) a fog nozzle as a straight stream
3) a narrow fog stream
4) a wide fog stream
Task steps
1 point each
1. Positions themselves on same side of hose line w/another
trainee on the nozzle and another trainee as a backup
2. Communicates with other trainees that they are ready
3. Twist the stream adjustment ring to adjust the stream
pattern to a
a. Solid-stream (solid-stream nozzle)
b. Straight stream (fog nozzle)
c. Narrow fog-stream (fog nozzle, 15 to 45 degrees)
d. Wide fog stream (fog nozzle, 45 to 85 degrees)
4. Aims the nozzle at the designated target
5. Opens the nozzle fully
6. Directs the stream at the target for 15 seconds
7. Shuts off the nozzle so that a water hammer is avoided
8. Rotates through all three (3) positions on the hose line
Total points possible 32 (Four skills worth 8 pts. each)
Instructor’s Signature
Date
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Name_______________________________________
Date_______________________________
Discussion Rubric
Objectives
4 pts.
Excellent
3 pts.
Good
2 pts. Needs Some
Improvement
1 pt. Needs Much
Improvement
N/A
Pts.
Participates in group discussion
Encourages others to join the
conversation
Keeps the discussion progressing
to achieve goals
Shares thoughts actively while
offering helpful recommendations to
others
Gives credit to others for their ideas
Respects the opinions of others
Involves others by asking questions
or requesting input
Expresses thoughts and ideas
clearly and effectively
Total Points (32 pts.)
Comments:
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