Physics 102/202 Heat
Activities
Name_______________________________
Class_______________________________
Lab Partners_________________________
INTRODUCTION TO HEAT AND TEMPERATURE
To find out
Materials
Investigation 1: Temperature and Thermal Equilibrium
How to measure temperature with a temperature probe
How to graph temperature over time
How quickly the temperature probe responds
The meaning of thermal equilibrium
Logger Pro software
2 stainless steel temperature probes (fast response if available)
1 - 500 ml beaker for room temp distilled water
1 - 50 ml graduated cylinder
1 - 150 ml beaker for non-insulated heat experiments
1 film container
1 Heat Pulser
Lab Pro
2 small foam or other insulated cup, 1 drink cozy
Hot plate, tea kettle
Plastic Beaker for dumping water
ice water, hot water, room temperature water
Introduction
Measuring Temperature: Temperature is a quantity familiar to all of us. Thermometers register changes in
temperature by using materials that change in some way as they are heated or cooled. For example, the
column of liquid in a common thermometer expands when heated and contracts when cooled. Thus the
length of the column is longer or shorter depending on the temperature, and the instrument can be used
to measure temperature. If the length of the column is associated with standard temperature units and
scales such as Fahrenheit or Celsius, the thermometer is said to be calibrated.
Thermometers: There are many types of thermometers based on different physical properties that change with
temperatures. You will be using an electronic temperature probe connected to the computer as a
thermometer. The probe works much like the digital thermometers available from hardware stores.
As the temperature probe is heated or cooled its electrical properties change, and these changes are
displayed on the computer screen as temperature readings. Using this temperature probe, you can
display the temperature of the objects you touch with the probe. You can also have the computer
display the measurements you take as graphs.
Thermal Equilibrium: The temperature probe always measures its own temperature. When you touch the probe
to something, it takes a few seconds for the probe and the object to reach a common temperature.
After this happens the probe is said to be in thermal equilibrium with the object it is touching. Objects
reach thermal equilibrium by transferring heat back and forth. An object with the higher temperature
transfers heat to an object with a lower temperature. To make accurate temperature measurements it is
important to wait until the temperature reading of the probe remains fairly constant (until the
temperature probe and the object are in thermal equilibrium).
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Physics 102/202 Heat
Activity 1 Temperatures Around You
Activities
Warning!! water and computers do not mix well. Keep all water as
far away from the computer as possible.
Warning 2 !! make sure that the heater is unplugged. The heater
should be immersed in water whenever it is plugged in.
Before you get started, pour a pot full of water into a coffee maker and
turn it on. Also set a teapot on a hot plate. Adjust the hot plate
thermostat to the mid range scale, about 3, and once the water comes
through the coffee maker, pour it into the pot on the hot plate. Adjust
the thermostat to keep the water at about 80°C and refill the coffee maker for the next person.
In this activity you will see how the temperature probe works and measure some temperatures around
the laboratory.
1. Set up the temperature probe. Plug the temperature probes into CH1& 2 of the LAB PRO. Open
the Logger Pro software. Temperature-time axes should appear on the screen. If you do not get
temperatures for Ch1 and Ch2 on the vertical axis you can manually choose the temperature probes
from Set Up Sensors of the Experiment menu. Simply click on the white box associated with each
channel, select Show all interfaces, and then arrow down to the stainless steel temperature.
You will now see a digital readout near the top of the screen. This readout will correspond to the
standard Celsius temperature scale, where water freezes at 0°C and boils at 100°C, only after
"calibration". The factory calibration should work fine for our purposes.
2. You will only need to use the digital readout for one of the probes in this part of the experiment,
but when you are ready to make a temperature-time graph, you just need to click on Collect.
3. Find the temperatures of objects around you. Touch the tip of the probe to a variety (at least 5) of
objects around you. You may put the probe into water. Remember: wait until the probe reading
becomes steady if you wish to measure accurately.
4.
Fill in the following table. Also measure the temperature of:
•
Ice water (be sure to stir).
•
Your armpit (clamp the probe tightly under your arm).
•
The hottest and the coldest things near you.
Object
Temperature
How does it feel? (hot?
warm? cold?)
ice water
armpit
___________________
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Physics 102/202 Heat
Question
Activities
Are your measured temperatures of ice water and of your armpit what you expected? Explain
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Activity 2
Reaching Thermal Equilibrium
When a nurse pops a thermometer in your mouth, why doesn't he pull it out and read it immediately?
In this investigation you will examine how long it takes for the temperature probe to reach thermal
equilibrium under different conditions.
Up until now, you have been looking at individual temperature readings. You can also display a
history of the probe's temperature by graphing the temperature readings over a period of time. Such
temperature histories are often more useful for understanding temperature changes than single
readings.
Prediction Suppose the temperature probe has been in hot water for awhile. You want to measure water and
air which are both at room temperature. Will it take longer for the probe to reach room
temperature in water or air? Explain your reasoning.
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Test your prediction.
1.
Measure room air temperature: ________ °C
2.
Set up cups of hot water and room temperature water (water which has been sitting out in the room
for a long time). Place the probe in the hot water and stir until the probe reaches a steady temperature.
3.
Begin graphing temperature. Set data collection length for 50 sec using the data collection command
of the Experiment menu. Click on Collect button.
4.
After the graph begins to appear on the screen, Quickly move the probe to the room
temperature
water. Stir and graph for the remainder of the 50 sec. Save your graph for comparison using store
latest run from the Experiment menu.
Approximately how long did it take the probe to reach room temperature? _______sec
5.
Now repeat this experiment (Using fresh hot water or water that has about the same initial temperature
as the water had at the start of the first experiment) moving the probe from the hot water to air instead
of room temperature water. Start graphing with the probe in the hot water. Pull it out and away from
the hot cup at the same moment as before, and dry the tip quickly.
Compare the time it took to reach room temperature to the time it took earlier when the probe was
placed in room temperature water. Does the probe ever even get to room temperature?
________________________________________________________________
Save your graph for another comparison using store latest run from the Experiment menu.
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Physics 102/202 Heat
Activities
6.
Repeat this experiment again. (The one in step 5) This time, wave the probe vigorously in the air after
drying it. (Be careful not to be so vigorous that you damage the probe)
Did it cool down at the same rate as without waving the probe?
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Questions
Why do you think that the probe takes longer to reach room temperature in air than it does in
water? (Q2)
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Why do you think that waving the dry probe around in the air makes it cool at a different rate?
What does this do to the air near the probe? (Q3)
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Activity 3
Temperature Change and Heat Flow
In this activity you will examine more carefully the interaction between hot and cold objects.
Prediction Suppose you have a mass of hot water and a larger mass of water at room temperature. The two
samples of water are mixed together. What can you say about the final temperature if the hot water
is 80°C and the room temperature water is 20°C? Will it be midway between 80°C and 20°C? Or
will it be closer to 80°C or closer to 20°C? Why?
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Test your prediction. You could actually mix the two samples of water and find the result. By not
mixing the two samples but putting them in separate containers in thermal contact, you will get the
same result and you can study how the temperature of each sample changes. Try the method
described below.
1.
Set up the cup and film container. Use the film container to pour enough cool room
temperature water into the insulated cup (cozy) so that the film container can just be
submerged in the water. Measure the water in integer numbers of film containers.
How many full film containers full of water did you put in the cup? ________
Tools for Scientific Thinking
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Physics 102/202 Heat
Put a temperature probe in the water.
Activities
Put a second temperature probe through a hole in the film container cover. It should be a tight fit.
2.
Set up the probes and Logger Pro. Set up to display and graph both probes by setting the y-axis
title (clicking and dragging on it) to read Temperature 1 &Temperature 2 (both of the above).
A time axis of 0 to 5 minutes and temperature axis of 20° to 80°C should work. You’ll need to
change the collection length from the data collection command of the Experiment menu.
3.
Carry out the investigation. Fill the film container with water near 80°C, and seal it with the cover
and probe. Quickly do the following.
Record the initial temperatures: Hot: ________ Cool: ________
Start graphing by clicking on collect, and then submerge the film container in the cup. Gently
move the container up and down to mix the water in the cup for the rest of the investigation.
When you are done, neatly sketch your graphs on the axes below (label the time axis to suit your needs).
Questions
Did the final temperatures of the hot water and cool water agree with your prediction? Explain.
(Q4)
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As the hot water cools down, what happened to the cool water? Explain this in terms of heat flow.
(Q5)
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_______________________________________________________________________
Tools for Scientific Thinking
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Physics 102/202 Heat
Activities
INTRODUCTION TO HEAT AND TEMPERATURE
To find out
Materials
Investigation 2: The Difference Between Heat and Temperature
Whether all heat transfers cause a temperature change
When different amounts of heat flow result in the same temperature change
The difference between heat and temperature
Logger Pro software
Stainless steel temperature probes
Lab Pro
Heat Pulser (relay box and heater)
150 ml glass beaker(not insulated, not foam)
hot water (about 80°C)
foam or other insulated cup
Introduction In this investigation, you are going to transfer heat to a cup of hot water. You can do this by
using pulses of heat from a water heater. In Logger Pro, you must click on the Collect button to
make the Pulse button functional. Now, each time you click on the Pulse button, the heater coil
turns on for a few seconds, and a certain amount of heat is transferred to the water — the same
amount each time.
WARNING!! DO NOT PLUG IN THE
HEATER OR CLICK ON THE HEAT
BUTTON UNLESS THE HEATER IS IN
THE WATER.
Prediction
If you transfer heat to water in a cup at the same rate as it is leaving, what will happen to the
temperature of the water? What will happen if you transfer in more heat than is flowing out?
Less than is flowing out?
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Physics 102/202 Heat
Activities
Activity 1
Keeping Hot Water Hot
You are going to try to keep hot water at a constant temperature by transferring heat with the Pulser to
replace the heat that flows out. During the 2 minutes the experiment lasts, someone must stir the
water continuously to keep all of it at the same temperature.
Before you start, measure the room air temperature: _________
1. Prepare to graph with Logger Pro. Clear previous graphs from the screen. Set the time axis and
collection length to 120 seconds (from the data collection command of the Experiment menu). Set
the temperature axis from 70° to 90°C.
Set up the Heat Pulser. The Heat Pulser is controlled by a remote control switch. Plug the heater
into the Heat Pulser that is plugged into an A.C. outlet. Make sure that the heater is always submerged
when it is plugged in. Connect the Heat Pulser into DIG/Sonic1 port of the Lab Pro interface. Use Set
Up Sensors on the Experiment menu (show all sensors) to select Heat Pulser for the DIG/Sonic1
port. In the Show All Sensors Dialog box click on the white square associated with DIG/Sonic1,
choose sensor, and select Heat Pulser. Once the Heat Pulser is assigned to the DIG/Sonic1 port you
can change the heat pulse duration by clicking on the square box associated with the DIG/Sonic1 port
in the Show Sensors dialog box. Set the Pulse duration to 2 sec.
2. Measure the hot water temperature. Start with 100 ml of hot water at about 80° C in a uninsulated (not
foam) small beaker. Put the heater into the water, and plug it into the pulser just before starting. (Use
the heat pulser to warm the water to about 80°C before you start, if necessary. The Pulse button is up
by the Collect button and again, you must click on the Collect button to make the Pulse button
functional)
Water temperature at the start: ________ °C
3. Keep the hot water hot. Click on Start to begin graphing. Try to keep the water temperature constant
(within a degree). Click on Pulse when you need to transfer more heat.
Note: You must wait for the Pulse button to return before you can pulse the heater again.
The computer will make a small square on the graph when you click on Pulse, and will keep track of the
number of pulses you use. Keep stirring!
Results
How many heat pulses did you need to keep the hot water at a constant temperature for 120 seconds?
_________
Draw the approximate
graph of the water's
temperature. Show with
arrows approximately
where you put in heat
pulses. Fill in the
temperature scale and label
the time axis to suit your
needs.
Tools for Scientific Thinking
This activity was modified by Clark College Physics
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Heat and Temperature 2/92
© 1987-92 CSMT Tufts U
Physics 102/202 Heat
Activities
Questions When you heat water in a teakettle on the stove, the temperature of the water rises. Why
didn't the temperature rise when you transferred heat to the water in the cup by using the pulser
during this activity? Explain where the heat is going. (Q1)
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In this experiment you are working as part of a feedback loop to keep the temperature of the water
constant. Can you think of a device in your home that operates in a similar way? (Q2)
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Activity 2
Heating Up Water
In this activity you will try to raise the temperature of water in an insulated cup by transferring heat
to it from the Heat Pulser. You will examine how the temperature changes as heat is transferred at a
steady rate.
Prediction Heat is transferred to water in a small, perfectly insulated cup (no heat can leak in or out) at a steady
rate for 80 seconds, and then no more heat is transferred. Sketch below your prediction for the graph
of the temperature of the water as a function of time.
Check your prediction.
Tools for Scientific Thinking
This activity was modified by Clark College Physics
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Heat and Temperature 2/92
© 1987-92 CSMT Tufts U
Physics 102/202 Heat
Activities
1.
Prepare to heat the water. Put a probe and the heater into a small foam(insulated) cup. Add 100 ml
of water near room temperature to the cup. For stability of the small cup, place it into one of the
larger styro-foam snuggies. Be sure that the water
covers the coils of the heater.
2.
Prepare to graph with Logger Pro. Set the time axis and collection length to 150 seconds, and set the
temperature axis from 10°C to 40°C.
Set the Pulse Length . . . to 5 seconds (clicking on the square box associated with the
DIG/Sonic1 port in the Set Up Sensors dialog box [Experiment menu]). Only Temperature 1 should
be graphed.(click on the title of the vertical axis and select temperature 1. If you want to plot both in
the future click on the y-axis label and select both.)
Warning: Be sure that the heater is only plugged in when it is in the water.
3.
Measure the temperature of the water. Initial Temp.: ________ °C
4.
Start graphing (Collect). Stir the water vigorously during the entire time the computer is graphing the
temperature, now and during the rest of these investigations.
For the first 10 seconds don't pulse the heater. Just watch the temperature when no heat is transferred.
Then pulse the heater every 10 seconds for a total of 4 heat pulses.
5.
Measure the final temperature of the water. When the temperature stops increasing, record it. Final
temperature: ________ °C (Use the digital display.)
Using store latest run on the Experiment menu, store your data for future comparison.
Calculate the temperature change of the 100 grams of water: ________ °C
Also calculate the temperature change per heat pulse: ________ °C/pulse
6.
Sketch on the axes below the shape of the temperature-time graph. Label the time axis to suit your
needs.
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Physics 102/202 Heat
Questions
Activities
Why did the temperature of the water rise during this activity while in Activity 1 it remained
constant as heat was transferred? (Q3)
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Did the shape of the graph agree with your prediction? Describe any differences. Will the shape
be different from the shape of the graph you would get if you took the temperature probe at room
temperature and put it into warm water? Explain. (Q4)
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Prediction
Suppose you started with twice as much water (200 grams) at room temperature, and heated the
water to the same final temperature. How many heat pulses would you need to transfer? Four?
More than four? Less than four? Explain how you arrived at your prediction.
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Physics 102/202 Heat
Activity 3
Heating Up More Water
Activities
Test your prediction by repeating Activity 2 using 200 grams of water.
1. Prepare the water and cup. Begin with 200 grams of water at room temperature
same starting temperature as before) in the same foam (insulated) cup.
2.
Prepare to graph. Don't change any of the settings from Activity 2.
3.
Measure the temperature of the water. Initial temp.: ________ °C
(about the
4.
Start graphing (collect). Again wait 10 seconds to begin transferring pulses. Then pulse the heater
every 10 seconds until the water reaches about the same final temperature as in Activity 2.
(Remember that the temperature will continue to rise for awhile after the last pulse is transferred.)
5.
Measure the final temperature of the water. Record the temperature once it has stopped increasing.
Final temperature: ________ °C. (Use the digital display.)
Calculate the temperature change of the 200 grams of water: ________ °C
Also calculate the temperature change per heat pulse: ________ °C/pulse
6.
Sketch your graph on the axes on the previous page. Use a dashed line.
7.
Record data in the table below so that you can compare the results of Activities 2 and 3.
Mass of Water (g)
100
200
Question
Number of Heat
Pulses
Added
4
Change in
Temperat
ure (°C)
Temp. Change Per
Pulse
(°C/pulse)
Did your results agree with your prediction? Describe any differences. (Q5)
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Assuming that very little heat leaked from the insulated cup, how do you explain your observation that
different amounts of heat (number of heat pulses) caused the same temperature change? (Investigation2:
Activities 2 and 3) (Q6)
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Tools for Scientific Thinking
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Physics 102/202 Heat
Activities
Are heat (that which is transferred by the Heat Pulser) and temperature (that which is measured by the
temperature probe) the same thing? Explain your answer carefully in terms of your observations of
Investigation 2: and Investigation 1: Activity 2. (Q7)
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Since heat was transferred by the Heat Pulser at a steady rate in time, the time and the amount of heat
transfer are proportional. From your graphs, what type of relationship exists between the temperature
of the water and heat transferred? Explain. (Q8)
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How does the temperature change for equal heat transfer to different amounts of water depend on the
mass of the water? If you double the mass of the water, and transfer the same amount of heat, what
happens to the temperature change? Answer in words and write a mathematical relationship between
the temperature change (∆T) and the mass (m) for a fixed amount of heat transferred. (Hint: look at
your data for Temperature Change per Pulse and at the slopes of your graphs.) (Q9)
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Physics 102/202 Heat
Activities
INTRODUCTION TO HEAT AND TEMPERATURE
Activity 4 Measuring Heat Flow — Specific Heat
The amount of heat that it takes to raise the temperature of a certain mass of material is given by:
Q mc T
Here, Q is the heat flow in Joules, m is the mass of material in kg , c is the specific heat capacity which
varies depending on the material and ∆T is the temperature change.
In this section you will measure temperature change of a known quantity of water to compute Q, the
energy transferred into the water using the equation given above. If the time is known the average
power can be computed. This will allow us to compute the power of the electric heater in Joules/sec.
(Watts)
You will need the specific heat of water, it is 4186 Joules/kg/C
Carefully heat a known mass of water for a given number of 5 second heat pulses given in quick
succession (see table). Compute the energy in Joules transferred as heat. Fill in data table below repeat
twice. Start with fresh water each time. Don't forget to stir!
Mass, m, of
Water (g)
Number of
Heat Pulses
100
140
160
6
6
6
Change in
Temp. (°C)
Q, Heat
Transferred
(Calculated)
(Joules.)
Q, Heat
Transferred
per Pulse
(Joules.)
Find an average value. of heat energy transferred per five-second pulse: ________
Determine the rate at which the heater transfers heat. Use your average value above and the length of a
heat pulse (5 sec) to determine the rate — in Joules/second — at which the heater transfers heat. This is
the power rating of the heater.
Power rating of the heater: ______________ Joules/sec (Watts)
Compare (% Diff) this with the known rating that is written on the plastic part of the heater.
Try to explain why your calculated value is slightly different.
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Tools for Scientific Thinking
Heat and Temperature 2/92
This activity was modified by Clark College Physics
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Physics 102/202 Heat
Questions
Activities
Show all of your calculations for the following.
How much heat must be transferred to 300 grams of water to raise its temperature by 25°C?
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How many five-second pulses from your heater would be needed in Question 9?
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If the heater were plugged directly into the wall outlet, how many seconds would it take to raise the
temperature of the water in Question 9 by 25°C? Explain your reasoning. (Q11)
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HOMEWORK FOR INTRODUCTION TO HEAT AND TEMPERATURE
1.
Approximately what is human body temperature on the Celsius temperature scale? ________
2.
Which is better at transferring heat, water or air? With this, explain the difference in the length of time
required for the temperature probe to reach thermal equilibrium in air, versus water.
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Physics 102/202 Heat
Activities
3.
If you put a cup of hot chocolate at 80°C on a table in a room at 20°C you already know it will cool
down.
a.
How cool will the hot chocolate get? ____________
b.
If you put it outside where the temperature is 5°C, how cool will it get? _________
c.
Compare the initial rates of cooling in (a) and (b). Are they the same or is one larger? Explain.
d.
_____________________________________________________________________________
Where does the heat go as the hot chocolate cools down?
e.
f.
_____________________________________________________________________________
Sketch a graph of the temperature of hot chocolate vs. time, starting at 80°C and placed outside
where the temperature is 0°C. Label the time axis with numerical values that make sense.
Explain the shape of the graph and the change in the rate of cooling in terms of your observations
in this lab.
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6.
A pot of water is heated on the stove. After the temperature of the water has risen a certain amount, the
temperature stops rising even though heat continues to be transferred. Explain how it is possible to
transfer heat without changing the temperature of the water.
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Tools for Scientific Thinking
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