Name ____________________________________
Date _________________
FINAL CHAPTER PROJECT
Here is your chance to use the chemistry you know to determine, from the standpoint of a product
developer, the most cost-effective materials for a hot or cold pack.
Making a hot or cold pack
Purpose: To determine which chemical produces the most efficient hot or cold pack for the cost of
reactants
Materials: 2 Styrofoam cups, 1 large beaker, thermometer or temperature probe and data collection
device, balance
You will be assigned either a list of chemicals (calcium chloride, lithium bromide, and lithium
chloride) or three of the following four chemicals: potassium nitrate, ammonium nitrate, sodium acetate,
and potassium chloride. You will use about 2 grams of each chemical for each trial (about 4 grams of
each chemical total).
Safety: Wear goggles while in lab. Avoid contact with or inhalation of chemicals. Wash hands after
lab and report any incidents to your teacher.
Procedure:
1. Find the mass of 2 Styrofoam cups stacked together (your calorimeter).
2. Add between 2 and 3 grams of your assigned chemical to the cup. Record the exact mass of the cup
with the chemical.
3. Place the cups in a larger beaker for stability.
4. Add about 50 mL of water to a graduated cylinder. You don’t need to record the volume; you’ll
find the mass in a later step. Leave the water in the graduated cylinder for now.
5. If using thermometers:
a. Record the initial temperature of the water in the graduated cylinder.
b. Add the water to the Styrofoam cup and stir with the thermometer.
c. Observe the temperature as it begins to change while stirring the water in the calorimeter. If it is
increasing, record the highest temperature it reaches. If the temperature is decreasing, record
the lowest temperature it reaches.
6. If using temperature probes with a data collection device:
a. Place the probe into the graduated cylinder. Start the data collection.
b. Add the water to the Styrofoam cup and stir with the temperature probe.
c. Observe the temperature readout until it levels off. Stop the data collection.
7. Use the “statistics” function of your data collection device to find the minimum and maximum
temperatures during collection. You will need to decide, based on your graph/data, which is the
initial temperature (the min or max) and which is the final temperature (the min or the max). Record
the two temperatures appropriately.
8. Find and record the mass of the two cups with the chemical and the water.
9. Repeat the process so that you have completed two trials for each of the three chemicals you were
assigned. Make sure you thoroughly dry the cup between each trial (or use a new cup).
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Data:
Chemical 1:
_____________
Chemical 2:
_____________
Chemical 3:
_____________
Trial 1
Trial 1
Trial 1
Price of chemical ($)
How many grams for that
price?
Trial 2
Trial 2
Trial 2
Mass of calorimeter (g)
Mass of calorimeter and
chemical (g)
Initial temp of water (°C)
Final temperature of water
(°C)
Mass of calorimeter,
chemical, and water (g)
Results/Calculations:
1. Find the mass of water that changed temperature in the calorimeter for each trial.
2. Find the enthalpy change of the water in the calorimeter for each trial.
3. Find the mass of chemical used for each trial.
4. Find the cost of the chemicals used for each trial.
Copyright © 2009 by Kendall Hunt Publishing Company
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5. Find the enthalpy change per cost of chemicals used for each trial.
6. Find the average enthalpy change per cost of chemicals for each chemical.
Discussion questions:
1. Did you produce a hot pack in your experiment or a cold pack? Give evidence to support your
answer.
2. Was the process endothermic or exothermic?
3. Did the hot or cold pack use a chemical process or a physical process? Explain what occurred
during the process to produce or remove energy from the calorimeter.
4. Which of the chemicals makes the best hot/cold pack for the price—which chemical would you
choose to make a hot or cold pack?
5. Look at the information in the following table. Would you still choose the same chemical as your
top choice? Why or why not?
6. Explain how you would change the setup of the process to make a real hot pack or cold pack;
instead of using cups and pouring the water in, how could you use the chemical and the water to
make a realistic hot/cold pack? Describe how it would work.
Copyright © 2009 by Kendall Hunt Publishing Company
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7. Create two class histograms (one for “cold” and one for “hot”) to see if the class is in
agreement about the most efficient chemical (see Lab 2.7, Discussion question 5). Describe
the class results. Is there a clear mode? If not, suggest possible reasons.
Chemical
Hazardous if
Ingested?
(yes/no)
Listed symptoms
CaCl2
Yes
Nausea and vomiting
LiBr
Yes
Nausea, vomiting, rash, ringing in ears,
diarrhea, drowsiness, coma
LiCl
Yes
Gastrointestinal irritation
KNO3
Yes
Violent gastroenteritis
NH4NO3
Yes
Gastrointestinal discomfort
NaC2H3O2
No
Some irritation
KCl
Yes
Gastrointestinal irritation, vomiting,
circulatory problems, heart problems; may
be fatal
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