and calibrate their own bulb thermometers.
Students will be able to:
understand how a bulb thermometer works.
create a temperature scale for their thermometer.
convert between Fahrenheit and Celsius temperature scales.
thermometers and temperature probes for display (do not use mercury
- ballpoint pen or pencil
- 3 hot
- 3 large
containers (for warm water)
- copy of the "Building a Bulb Thermometer" student handout
- copy of the "Calibrating Your Thermometer" student handout
- 170 g (6 oz) baby food jar
- room-temperature water
- 1000 ml
- plasticene or modeling clay
- food coloring
- plastic pipette
- 8-cm x 13-cm (3-in x 5-in) index card
- ballpoint pen
- thermometer (to measure water temperature)
While humans have always wondered
about cold, the earliest known studies about cold began in the 1600s. One of
the first steps toward understanding cold was to determine how to measure it.
Grand Duke Ferdinand de Medici invented the first accurate thermometer in 1657.
Now thermometers are everywhere.
Three main scales are in use today:
Fahrenheit, Celsius, and Kelvin. A pioneer in developing alcohol and mercury
thermometers, Daniel Fahrenheit devised a scale in the early 1700s where he
marked zero to represent the temperature of equal parts of ice, water, and
salt. On this scale, the freezing point of water is 32 degrees, and the boiling
point is 212 degrees. In 1742, Anders Celsius developed a scale where he
labeled the freezing point of water as 100 degrees and the boiling point of
water as 0 degrees, and marked off 100 equal degrees between them.
(Today's Celsius scale reverses the 0 and the 100.) The third type of scale
is named after Lord Kelvin, who proposed the Kelvin scale in the mid-1800s. The
Kelvin scale—which is based on the Celsius scale, but has no negative
numbers—is widely used by scientists. The Kelvin scale uses the triple
point of water (the temperature at which water exists simultaneously as a
solid, liquid, and gas, 273.16 K) and the boiling point of water (373 K) as its
fixed points. Zero on the Kelvin scale is considered to be absolute zero, the
point at which all molecular motion stops.
In this activity, students build
and calibrate a simple bulb thermometer.
container tops for students' bulb thermometers prior to the activity.
While the lid is still on the jar, tap the nail into the middle of the jar lid.
Using the hammer to tap the top of a ballpoint pen or pencil so that the tip is
inserted to the point shown (see illustration). This will open the hole just
enough so the straw will go through. While a larger hole can be plugged with
clay, there is a much higher chance of the liquid leaking out during the experiment
if the hole is even a bit wider than the straw. Remove the jar labels
(otherwise they will fall off while in the warm water bath).
or pencil in the jar lid to the point shown to create a hole with the proper
to brainstorm all the thermometers that can be found in their homes. (Some
examples include thermometers to measure outside temperatures, thermometers to
measure body temperatures, and kitchen thermometers used to measure food
temperatures in meat and candy.) Ask
students to find as many types of thermometers as they can in their homes and
record the range of temperatures on each and the temperature that the
thermometer reads when found.
thermometers you brought in. Make a list on the board of all the thermometers
students found, and show a sample of each if you have one. Have each student
report temperature ranges and the temperature reading of the thermometer. Which temperature scale does each use (Fahrenheit or Celsius)? What
are the similarities and differences in the temperature ranges on each
similar were their temperature readings when they were found? What would
explain any differences?
students that all thermometers depend on some material that changes their
properties when their temperatures change. A liquid bulb thermometer, such as
the classic mercury thermometer, relies on the fact that liquids expand as they
get warmer and contract as they get colder. Students will make a homemade
liquid bulb thermometer in this activity.
students into teams. Provide each team with the handouts and materials listed.
Have students make their thermometers. Before students calibrate their
thermometers, check each team's thermometer to make sure that the clay is
well sealed around the straw, that the jars are as tightly sealed as possible,
and that the water levels are at about halfway up the straw.
warm water baths at a station in the room for students to use to calibrate
their thermometers; the water should reach at least halfway up the jar but not
go over the top (remember to take into account how many students may be using
the warm water bath at once as this will raise the water level). Use a hot
plate to keep the warm water bath between 45 and 50 degrees C. Keep an eye on
the warm water bath during the activity to ensure it is maintaining its
temperature (using as large a container as possible will help keep the bath a
students make their own ice water baths in beakers. Provide paper towels near
each bath for cleanup. Students should do the ice water baths first; if they do
the warm water bath first, it will take a long time for the liquid in the jars
to cool enough to show a noticeable decrease in volume.
students have used their reference thermometers to calibrate their homemade
thermometers, review answers to the questions on the student handout. Explain
the three most typical temperature scales used (see Background for
more information). What would each of the three different scales be good for
measuring? What would their homemade thermometers be good for measuring? (Their
thermometers would be best for measuring a very narrow temperature range, such
as how the temperature in the classroom changes throughout the year.)
To illustrate how the first universally accepted temperature scales were
invented, show students the portion of the program at right that presents how Daniel
Fahrenheit and Anders Celsius came up with their scales.
have viewed the video, ask them what the value is in having everyone agree to
use a specific scale. (A universally accepted scale means that the
thermometer can serve as a common reference point for temperature measurements,
thus providing a standard "language" for temperature.)
extension, work with the students to research how other types of
thermometers—like turkey pop-ups, Galileo thermometers, and digital
as it gets warmer, and contracts as it gets colder. As the water in the jar of
the thermometer got warmer, it expanded and had nowhere to go but up through
the straw. Then, when the thermometer was used to measure something colder, the
water in the jar got colder and contracted and sank down in the straw. This
principle of volume change can be used to measure temperature.
thermometers measure a change in temperature, the numbers used to describe that
temperature are arbitrary. The numbers are simply a scale that a set of people
agree to use; different scales are useful for different situations. The United
States, for example, uses the Fahrenheit scale, while much of the rest of the
world uses the Celsius scale.
scale was created for a thermometer built using a 170 gram (6-ounce) baby food
jar. The thermometer took about five minutes to come to temperature in the ice
water bath (4 degrees C) and about ten minutes to come to temperature in the
warm water bath (45 degrees C).
Student Handout Questions
What happened when you placed your thermometer
in the warm water bath? The ice water bath? What caused the changes you
observed? The liquid rose when the thermometer was placed in the warm water
bath and fell when placed in the ice water bath. The changes were caused by the
water increasing in volume when it was heated and decreasing in volume when
What are the limitations of your thermometer? Some
limitations include that the thermometer is slow to adjust to temperature
because of the large amount of liquid in the "bulb" portion, that
it could not measure below 32 degrees F (0 degrees C) or above 212 degrees F
(100 degrees C) because the liquid being used would freeze or boil at those
temperatures, and that because it is open at the top, water could evaporate
(thus rendering the scale inaccurate.
scales could you use to represent the different temperatures you measured? Temperature
scales are arbitrary; just about anything can be used to represent calibration
points as long as everyone in the group using the thermometer agrees on the
proposed scale. Students may suggest various number ranges, birthdates of class
members, names of scientists, or class members' initials.
Which of the following temperatures would you
prefer outside: 24 degrees Celsius or 70 degrees Celsius? Why? The best
temperature for being outside would be 24 degrees C, a comfortable outdoor
temperature (equivalent to 75 degrees F). Seventy degrees C would be scorching
hot (equivalent to 158 degrees F).
Considers whether there is an absolute hot, explores the
impact of refrigeration on society, explains what happens to atoms when they
reach ultracold temperatures, and provides student interactives related to the
science of cold.
Absolute Zero and the Conquest of Cold
Features a variety of educational resources, including
historical biographies, a time line of low-temperature physics, and companion
Absolute Zero and the Conquest of Cold
by Tom Shachtman.
Boston: Houghton Mifflin, 1999.
Features the struggles of
philosophers, scientists, and engineers over four centuries as they attempt to
understand the nature of cold. Served as the basis for NOVA's
"Absolute Cold" program.
The "Building a Bulb Thermometer" activity aligns with the following National
Science Education Standards (see
• Properties of matter
• Transfer of energy
History and Nature of Science
• Science as a human endeavor
• History of science
Classroom Activity Author
activity was adapted with permission from the "Absolute Zero Community
Education Outreach Guide," written by Karen C. Fox in collaboration with
Devillier Communications, Inc. The guide, as well as the companion "Absolute
Zero Science Educator's Guide" with classroom teaching strategies,
was designed for middle school teachers and informal educators. They can be