Understanding Boiling Point
Project Overview
This RWLO is structured to be incorporated into a lesson plan that discusses the
relationship between the states of matter: solid, liquid, gas, and plasma and the conditions
that result from a change of state (phase). The plasma phase will not be discussed here
because the high temperature-pressure conditions responsible for its existence are not
readily attainable. Specific attention will be given to the system conditions represented
by each segment observed in a heating curve for a pure substance. The discussion will
include the definition and system conditions of the temperature at which the (s  l) and (l
 g) equilibrium occurs. Water will be used as the specific example.
Raw data abstracted from CIESE’s International Boiling Point Project, will be used to
investigate the relationship between the boiling point of water and altitude. Students will
be required to graph and analyze this data to determine trends and relationships between
these two variables. Students will be asked to write a hypothesis describing the plausible
relationship between boiling point with any other measurable variable.
This RWLO assumes that students have previously developed an understanding of the
four states of matter, including all associated physical characteristics. It is assumed that
students are experienced in graphing raw data using a software program such as
Microsoft Excel.
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Student Learning Objectives
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Students will work in a collaborative group to construct a temperature measuring
device which can be used to measure the temperature change of water as a
function of time spent on a constant heat source. Students will also obtain the
boiling point of water.
Students will construct a portion of the heating curve for water and label the
segments making up the heating curve and explain how energy is being converted
in each segment.
Students will be able to explain the phenomena of boiling.
Students will research and record the theoretical value for the melting point and
normal boiling point of water and compare their boiling point value to the
theoretical value.
Students will be able to use International Boiling Point Project data to determine
the relationship between the boiling point of water and altitude by creating a twodimensional graph and finding the linear equation which best represents the data
set, and interpreting the quality of the data through analysis of the correlation
coefficient.
Students shall be able to use the International Boiling Point Project data to
qualitatively discuss the relationship between boiling point and atmospheric
pressure.
Students will propose a hypothesis that states the relationship between
atmospheric pressure and the boiling point of water.
Optional – Students will be able to calculate the vapor pressure of water as a
function of temperature by applying the Clausius-Claperyon Equation. Students
can check there calculations against experimental data found in the International
Boiling Point Project web site.
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Procedure
Time: 2 - 50 minute sessions
Materials: Computer with Internet Capabilities and Microsoft Excel and
experimental apparatus.
Background
 This RWLO is structured to be incorporated into a lesson plan that discusses the
relationship between the states of matter: solid, liquid, and gas and the conditions
that result from a change of state(phase). Specific attention will be given to the
system conditions represented by each segment observed in a heating curve for a
pure substance. The discussion will include the definition and system conditions
of the temperature at which the (s  l) and (l  g) equilibrium occurs.
 Raw data abstracted from CIESE’s International Boiling Point Project, will be
used to investigate the relationship between the boiling point of water and
altitude. Students will be required to graph and analyze this data to determine
trends and relationships between these two variables. Students will be asked to
write a hypothesis describing the plausible relationship between boiling point with
any other measurable variable.
 This RWLO assumes that students have previously developed an understanding of
the four states of matter, including all associated physical characteristics. It is
assumed that students are experienced in graphing raw data using a software
program such as Microsoft Excel.
Implementation: This RWLO can be used as a classroom exercise or initiated in the
classroom and completed as a homework activity in order to demonstrate the learning
objectives. Each student will be assigned to a group for this exercise. The members of
the group will obtain their data for the exercise as a collaborative unit. Each member of
the group will submit an individual summary report of their conclusions.
Steps:
 Assign each student to a collaborative group. Groups should contain no more
than four students. To maintain accountability and minimize conflict, assign
each member of the group a role to be used within the group for the duration of
that exercise. Ask the students to assemble into their respective groups and
supply each group with a copy of the group roles.
 Distribute the Heating Curve Experiment. Each group should: (1) read and set
up the experiment, (2) have the set up checked by the instructor before data
acquisition begins, (3) acquire temperature – time measurements until the
temperature reading is constant for at least two minutes at which time data
collection can stop, and lastly, (4) turn off the heat source and allow the water to
cool before dismantling the experiment. Data acquisition for the construction of a
Heating Curve for Water will take approximately 20 minutes depending on the
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heat source. Students can then create their own heating curve for water by
graphing time as the independent variable and temperature as the dependent
variable.
Provide students the links to these two power point resources: Heating Curve of
Water and Pressure – Boiling Point Relationship.
Distribute and review the Assignment Handout.
Discuss how the class will complete the activity. This will be depend on whether
the activity is entirely in-class or partially used as a homework assignment.
Students can explore the relationship between the boiling point of water and
altitude using near real time data collected for the International Boiling Point
Project maintained by the Center for Improved Engineering and Science
Education (CIESE). Describe all necessary information concerning the
International Boiling Point Project (IBPP) and provide the students with its
Web address (http://www.k12science.org/curriculum/boilproj/pastprojects.html).
Provide class time for each group to choose and download a data file from the
International Boiling Point Project. The International Boiling Point Project has
recent and numerous sets of archived boiling point data to choose from. All
members of the same group must use the identical data file.
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Content Material
Student Directions
 Assemble into your assigned group and review a copy of the group roles supplied
by the instructor to determine what your assigned roll is.
 Each group should (1) read and set up the Heating Curve Experiment, (2) have
the set up checked by the instructor before data acquisition begins, (3) record
temperature – time measurements until the temperature reading is constant for at
least two minutes at which time data collection can stop, and lastly, (4) turn off
the heat source and allow the water to cool before dismantling the experiment.
Students can then create their own heating curve for water by graphing time as the
independent variable and temperature as the dependent variable.
 Read the Assignment Handout provided. Your instructor will determine which
activities will be completed in class within your group and which will be
completed as an out of class assignment.
 Reassemble into your assigned group at a computer connected to the Internet and
access the International Boiling Point Project Web-site at
(http://www.k12science.org/curriculum/boilproj/pastprojects.html). Search the
project data by clicking on the PC user file data links. This information is
compiled and presented on the Web site in Microsoft Excel format. Each group
should retrieve one data set from this Web site. Allow time to create a scatter plot
of the data using Microsoft Excel. Some of the archived data sets are better
than others but all data sets should exhibit a correlation between altitude and
boiling point. The boiling point decreases as the altitude increases. Once your
group has completed the scatter graph, send enough copies to the printer so every
group member has one.
 Based on time and computer access, look at these two power point resources:
Heating Curve of Water and Pressure – Boiling Point Relationship.
 Complete the assignment.
Additional Resources
Back-up Web-site for the International Boiling Point Project data:
http://www.k12science2.org/curriculum/boilproj/pastprojects.html
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Assessment
Each of the bullets in the Assignment Handout can be used for assessment based on the
following rubric.
Heating Curve of Water: [5 total points]
 Record temperature, time data in a Microsoft Excel worksheet. Use the Excel
Chart Wizard to create a Heating Curve of Water by plotting temperature verses
time using time as the independent variable. Analyze the graph.
Preparation of the heating curve will be scored as follows:
5 pts = All of the requirements listed below have been fulfilled.
a) An Excel worksheet has been created and includes temperature – time date.
b) An x – y scatter plot of the temperature of water verses time of heating is
prepared correctly using the temperature as the dependent variable. The data
points are presented correctly.
c) The axes scale is appropriate for the data plotted. The scale uses the correct
number of place holders provided by the original data table.
d) Each axis is labeled or titled. The graph is given a title.
e) All appropriate units are provided in parentheses near the axis label.
4 pts = Four of the five requirements have been fulfilled.
3 pts = Three of the five requirements have been fulfilled.
2 pts = Two of the five requirements have been fulfilled.
1 pts = One of the five requirements has been fulfilled.
0 pts = None of the requirements have been fulfilled.
Define and Identify the Heating Curve: [7 points]
 Define and discuss each segment of the heating curve, including the definition of
melting point and boiling point. What do the plateaus on the graph represent?
How do you account for differences between your graph and the theoretical
graph?
Identification and identification of the segments of the curve will be scored as follows:
7 pts = All of the requirements listed below have been fulfilled.
a) Defined and identified the position of the boiling point.
b) Defined and identified the position of the melting point.
c) Identified the segment representing the heating of solid water.
d) Identified the segment representing the heating of liquid water.
e) Described where is the s  l plateau and what is occurring there?
f) Described where is the l  g plateau and what is occurring there?
g) Compared and commented on any differences in their heating Curve to the
theoretical Heating Curve.
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Each missing requirement results in the loss of one point.
Analyze the Graph: [5 total points]
 Using Microsoft Excel, create a scatter plot of the data [boiling point
temperature (oC), altitude]. Analyze the graph. Is there a correlation between the
boiling point of water and altitude? Is there a linear relationship between the
boiling point of water and altitude? How can you show that there exists such a
relationship? How can you determine the quality of the data? How good is the
data set?
Analysis of the graph will be scored as:
5 pts = All of the requirements listed below have been included.
a) The graph has been correctly presented.
b) The graph is correctly labeled and titled.
c) The student has commented on the correlation between boiling point and
altitude. The student has acknowledged a linear fit to the data.
d) The trend line has been created and the equation for the line presented on the
graph.
e) The student has commented on the R2 value calculated by Excel for the linear
fit and related this value to the quality of the data.
Each missing requirement results in the loss of one point.
Student Hypothesis: [10 total points]
 Is there another atmospheric variable that can be correlated to altitude? How
could you prove a correlation exists?
 Can you write a hypothesis relating the affect of pressure on the boiling point of
water? How can you prove or disprove this hypothesis? Search the supplied
references for examples to prove that there is a relationship between atmospheric
pressure and boiling point of water. Define normal boiling point. Design your
own experiment to prove or disprove the hypothesis.
Analysis of the hypothesis statement is scored as:
10 pts = All of the requirements listed below have been included.
a) The student has identified a correlation between boiling point and atmospheric
pressure. The student has included the reference from which the correlation was
obtained.
b) The hypothesis is clearly developed and complete.
c) The hypothesis is written in complete sentences.
d) The student has included a definition and known value for the normal boiling
point.
e) The student has provided convincing arguments based on their comparative data
analysis.
8 pts = Four of the five requirements have been included
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6 pts = Three of the five requirements have been included.
4 pts = Two of the five requirements have been included.
2 pts = One of the five requirements has been included.
0 pts = None of the requirements have been included.
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Links to Course Competencies
This RWLO assumes that students have previously developed an understanding of the
four states of matter, including all associated physical characteristics. It is assumed that
students are experienced in graphing raw data using a software program such as
Microsoft Excel.
This RWLO can be used in a chemistry or a physical science course. The RWLO is best
suited for a general chemistry course. Upon completion of this RWLO the following list
of competencies shall be met.
 Students will be able to work in a cooperative group.
 Students will be able to measure and record raw data and manipulate it to produce
a graphical relationship between physical state and temperature.
 Students will be able to apply the process of mathematical modeling to real-world
applications.
 Students will represent data sets graphically and explore the interrelationships of
these representations, and identify trends and relationships between variables.
 Students will be able to acquire the linear equation from graphical data and
interpret the quality of the data set using the correlation coefficient.
 Students will communicate inferences and convincing arguments that are based
on data analysis.
 Students will write a hypothesis stating the relationship between two variables.
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Supplementary Resources
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Here are two additional examples for the theoretical Heating Curve of Water:
Example 1, and Example 2. The difference between these heating curves is
dependent on the form of the information plotted as the x variable.
The temperature at which water boils is related to the vapor pressure required for
boiling, which is equal to the atmospheric pressure. For every 1000 ft increase in
altitude, the boiling point decreases by about 1oC.
The International Boiling Point Project Web site contains background information
about the collaborative project, both new and archived data, and many
supplemental links.
There is a Back-up site for the International Boiling Point Project.
The correlation between altitude and boiling point is a linear one. The theoretical
equation for this relationship is:[Tboiling point = −(0.0026 K/m)A + 373.15 K] where
A is the altitude in meters, K is temperature degrees Kelvin. This equation can be
derived from substituting the equation of ambient pressure into the ClausiusClaperyon Equation for water vapor.
Table 1, Table 2, and Table 3 relate the boiling point to atmospheric pressure.
Each Table is presented in varying units.
This Web-site contains directions on how to use its search engine to obtain
altitude data: www.topozone.com
A number of Web-based calculator sites are supplied to allow calculation of the
boiling point for specific altitudes and pressures. Site 1, Site 2, and Site 3.
An alternative approach at relating boiling point to atmospheric pressure can be
provided by applying the Clausius-Claperyon Equation for the relationship
between equilibrium vapor pressure and temperature. If it is theoretically
assumed that the equilibrium vapor pressure is equal to the atmospheric pressure,
then the temperature at that pressure must correlate to the boiling point.
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Recommendations
Implementation:
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This RWLO can be used in a chemistry or a physical science course. The RWLO
is best suited for a general chemistry course. The design of the RWLO requires
students to work cooperatively in a group to perform an experiment and then
identify and download a data file which each group will use to complete the
RWLO. Use approximately 5 minutes to assign students to groups, describe the
activity, and the assignment.
The RWLO is designed such that it could be completed entirely in class or the
second 50 minutes could be completed as an individual out of class assignment.
It is assumed that the Heating Curve Experiment and the acquisition of
International Boiling Point Project data file will be completed in class by
members of the same group. Graphical analysis and the development of a
hypothesis can be completed on an individual basis, whether in or out of class.
Viewing of the Power Point presentations: Heating Curve of Water and
Pressure – Boiling Point Relationship could take place within assigned groups
during their computer time or as a classroom presentation.
Print out all the required materials referenced in the content material section of
this RWLO. This includes: one copy of the group roles and the Heating Curve
Experiment per group, and one copy of the assignment handout for each student.
Back up:
 If the primary Web site for the International Boiling Point Project is unavailable,
the back up site is:
http://www.k12science2.org/curriculum/boilproj/pastprojects.html.
 As a precaution, print at least one copy of a data file from the International
Boiling Point Project in case the Internet becomes inaccessible.
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