Procedure Proposal Experiment 22

Medical Hot and Cold Packs for Dystan Medical Supply Company

Emily BeardenBrad ElliottJori Moore

Mary Anna RodenNolan Williamson

Thomas Knight

Due: February 15, 2013

Equipment:1. MeasureNet System: A system that allows one to collect date such as temperature, pH, and

enthalpy change, electronically and saved to a computer.

2. Calorimeter: The calorimeter is made of two Styrofoam cups and a lid made of cardboard so that

no heat escapes.

3. Magnetic Stirrer: A stir bar and a platform that spins the stir bar which stirs the solution

automatically.

4. Hot Plate: A device that heats materials for lab. It acts like a stove and allows one to boil water

and heat other solutions.

5. Beaker: A glass container that holds materials for the experiment.

6. Mass Scale: A device that is used to determine the mass of an object or substance.

MeausureNet Calorimeter

Magnetic Stirrer and Stir Bar Hot Plate

Beaker Mass Scale

Introduction

Cold and hot packs are an important part of everyday life. They both serve as simple remedies to

speed the healing process. Cold packs can be applied to injuries to reduce inflammation. When a cold

pack is applied, heat will flow from the injury site to the pack. This produces vasoconstriction of blood

vessels, reduces blood flow, and then allows the inflammation to decrease. Hot packs work in the

opposite way. Heat flows from the pack to the injury. Vasodilation of blood vessels occurs, increasing the

blood flow and allowing more oxygen to reach the injured area and speed healing.

Most packs contain two compartments; one filled with water and the other with a salt (ionic

compound). When the compartments are broken, a reaction will occur that either heats or cools the pack.

A pack that feels cold will contain an endothermic reaction inside of it. On the other hand, a pack that

feels warm will contain an exothermic reaction. The Dystan Medical Supply Company is a large supplier

of these packs. The company has hired us to determine what ingredients the different types of packs

should contain. We have been asked to test four different salts: ammonium nitrate, calcium chloride,

lithium chloride, and potassium chloride. When testing these salts, we need to determine if an

endothermic or exothermic reaction occurs. From this we can decide to use the salt as an ingredient in

either the cold pack or the hot pack.

The company has confirmed that each pack will contain 100 mL of water. We have to determine

how much salt is required to produce a cold pack that will reach 0oC and how much salt is required to

produce a hot pack that will reach 65oC. In addition, the price of construction has to be determined. Each

pack must cost less than $5 for the Dystan Company to make a profit.

One way to determine whether the dissolving of a salt in water is endothermic or exothermic is to

experimentally find the molar heat of dissolution. This is accomplished by using a calorimeter. In order to

use the calorimeter, the calorimeter constant (Ccalorimeter) has to be found. The equations for this are:

qcalorimeter=C calorimeter × ∆ Tcalorimeter

qcalorimeter=( mwarmwater Cwarmwater ∆ T warmwater )(mcool water C cool water ∆ T cool water)

After this is found, we can test each of the four salts in the calorimeter to determine whether is should be

used in a hot or cold pack. Our goal is to first determine qdissolution then to find the heat of dissolution. A

negative delta Hdissolution will be an exothermic reaction; this would go in a hot pack. A positive delta

Hdissolution will be an endothermic reaction; creating a cold pack. The equation for this would be:

∆ H dissolution=qdissolution

molesof substancedissolved

In order to determine the mass of salt necessary for the ice pack to reach 0.0°C and the mass for the hot

pack to reach 65°C, we must set the ΔHdissolution calculated in our trial equal to the ΔHdissolution of hot/cold

pack containing 100 mL of water and reaching a temperature of 65°C/0.0°C. This equation is given

below:

Cdissolution × M dissolution × ∆ T di ssolution

molesof substancedissolved=

Cdissolution(x+100 g water)dissolution ∆ Tdissolution

x grams of substance dissolvedg

molof substance dissolved

*The left side of the equation represents our data from the trial, and the right side represents our

hypothetical calculations. By plugging in either 65°C or 0°C (depending on if were solving for the hot or

cold pack), and then solving for the x value, we can calculate the mass needed to raise or lower the pack

to the specified temperature.

Our expectation is that ammonium nitrate is endothermic (+ value) and will be used in the cold

packs. The other three salts are predicted to be exothermic (- value) and will be used for hot packs.

Finding the Enthalpy of the Dissolution of a SaltCAUTION: Students must wear departmentally approved eye protection while performing this

experiment. Wash your hands before touching your eyes and after completing the experiment.

PART A: Determination of the Calorimeter Constant

1. Press the On/Off button to turn on the MeasureNet workstation.

2. Press Main Menu, the press F2 Temperature, next press F1 Temperature vs. Time.

3. Half fill a 150-mL beaker with ice and water. Press Calibrate to calibrate the temperature

probe. When prompted, enter 0.0°C as the actual temperature of the constant temperature

bath (ice water). Press Enter. Insert the temperature probe in the ice water. Swirl the

temperature probe until the temperature approaches and stabilizes near 0°C (it may not

read exactly 0°C). Press Enter.

4. Remove the temperature probe from the ice water bath.

5. Press SetUp to establish scan parameters for the experiment. Press F1 to set the limits for

the scan. Use the ← → keys to move from min to max or from X to Y. An * marks the

parameter selected to change at any time. The Y axis is for temperature. Set the min

temperature 2-3°C below the initial temperature of the substance that the probe is inserted

into. Press Enter.

6. Set the max temperature 2-3°C above the expected final temperature. Press Enter.

7. For example, to calibrate a Styrofoam cup calorimeter, the min temperature should be set

to 15-18°C, and the max temperature should be set to 70-75°C.

8. The X axis is for time. Set scan parameters from 0 seconds (min) to 500 seconds (max)

(if the experiment is completed before 500 seconds have elapsed, press Stop at any time

to end the experiment).

9. When all parameters are entered, press Display to accept all values. The MeasureNet

workstation is now ready to record a thermogram.

10. Obtain two Styrofoam cups and a lid from your instructor to serve as a calorimeter. Nest

one cup inside the other to construct the calorimeter.

11. 45-50 grams of tap water should be added to the calorimeter to serve as the cool water.

Record the exact mass of cool water to 0.001 significant figures.

12. Setup the magnetic stirrer/calorimeter assembly.

13. The temperature probe is inserted into a 2-hole stopper and secured to a ring stand with a

utility clamp. The temperature probe is inserted through the hole in the calorimeter lid.

Position the probe so that its tip is ~1 cm from the bottom of the calorimeter. Be careful

not to poke a hole in the bottom of the Styrofoam cup. A stir bar is placed in the bottom

of the calorimeter.

14. Obtain a hot plate and place it at least two feet away from the MeasureNet workstation.

15. Add ~ 60 mL of water to a clean, dry 150-mL or 250-mL beaker. Place the beaker of

water in a microwave and heat for two minutes. (If a microwave is not available, heat the

beaker of water on a hotplate.) Remove the beaker from the microwave. Using a

thermometer, make sure the water temperature is 45-60 °C above room temperature. If

not, heat the water for an additional minute in a microwave. This will serve as the hot

water.

16. The temperature of the cool water will be shown on the MeasureNet screen. Record it to

0.01 significant figures.

17. Using a cloth towel pour exactly 50.0 mL of hot water into a graduated cylinder.

Assuming the density of the hot water is 1.00 g/mL, determine the mass of the hot water

using the formula D= MV

. Record the calculated mass to 0.001 significant figures.

Measure the temperature of the hot water with a thermometer and record it to 0.01

significant figures.

18. Press Start on the MeasureNet workstation to begin recording the thermogram. Turn on

the power to the magnetic stirrer to a low to medium speed. Make sure the stir bar is

spinning without contacting the temperature probe or the walls of the calorimeter.

19. After 5-10 seconds have elapsed, raise the calorimeter lid, and quickly, but carefully,

pout the warm water (using a towel to hold the graduated cylinder) into the calorimeter.

Immediately replace the lid on the calorimeter. If a wire stirrer is used, you must

constantly move the stirrer up and down to stir the contents of the calorimeter.

20. When the temperature of the water has risen and stabilized at the equilibrium

temperature, press Stop to end the scan.

21. Press File Options. Press F3 to save the scan as a delimited file. You will be prompted to

enter a 3 digit code. The name of the file will be saves as a 4-5 digit number. The first 1-2

digits represent the workstation number, the last 3 digits is the 3 digit access code you

entered. Press Enter to accept your 3 digit number. You must use a different 3 digit code

for every file you save or you will overwrite the previously saved file.

22. Record the file name in your lab report. Note what type of information is contained in the

file in your lab report (i.e., thermogram for determining calorimeter constant).

23. Press Display to clear the previous scan. The station is ready to record a new

thermogram.

24. Using a magnetic rod, remove the stir bar from the calorimeter, and decant the water in

the calorimeter into the sink. Thoroughly dry the calorimeter. Perform a second trial to

determine the calorimeter constant by repeating Steps 2-19.

25. When you are finished with the experiment, transfer the files to a flash drive, or email the

files to yourself via the internet.

26. When two experimental trials for the calorimeter calibration have been completed, return

to the procedure in the corresponding laboratory experiment.

27. Steps 28-30 are to be completed after the laboratory period is concluded (outside of lab).

Proceed to Part B, Step 1, Determination of the Molar Heat of Dissolution of a Salt.

28. From the tab delimited files you saved, prepare plots of the temperature versus time data

using Excel (or a comparable spreadsheet program). Instructions for plotting temperature

versus time thermograms using Excel are as follows:

a. Open an Excel spreadsheet (i.e., worksheet).

b. Go to File Open, open a MeasureNet tab delimited file containing temperature

versus time data. Click Finish.

c. Copy the first two columns (containing time and temperature data) in the tab

delimited (text) file, and paste it into columns A (time) and B (temperature) in the

Excel worksheet. Close the tab delimited file.

d. Click on the “Chart Wizard” Icon.

e. Click on XY scatter plot. Click on the smooth line type.

f. Click Next. Then highlight all cells in columns A and B that contain time and

temperature data. An XY plot of the data will appear.

g. Click Next. Click Titles. Chart Title is the name of the plot. Enter a name for your

plot (i.e., Calibration of Calorimeter). The x-value box is for labeling the X axis

(Time, s), and the y-value box is for labeling the Y axis (Temperature, °C) on

your plot.

h. If you wish to remove the gridlines, Click on Gridlines and click on the axes that

are checked to turn off the gridlines. This is a suggested cosmetic function, it is

not necessary.

i. Click Legend. Click on Show Legend to remove the legend, it is not required for a

single curve.

j. Click Next. You can save the plot as a separate sheet which can then be printed.

Alternatively, you can save it as an object in the current worksheet. The plot will

appear in the Excel worksheet beside columns A and B. If you save the file in this

manner, you will have to select and highlight a copy area box (i.e., highlight the

plot area) under Page Set-Up to print the plot.

k. Alternatively, you can select the plot, copy, and paste it into a “Word” document,

and print the plot from within the word document.

l. YOU MUST TYPE OR WRITE the ΔT value on your plot.

m. Repeat Steps a-l to prepare the remaining thermograms.

29. Determine the equilibrium temperature of the hot-cold water mixture in the calorimeter.

Determine the temperature changes for the warm and the cold water. Record these

temperatures to 0.01 significant figures.

30. Determine the calorimeter constant in J/°C for each trial using the formulas below. Then

determine the average calorimeter constant.

C cal orimeter=qcalorimeter

∆ Tcalorimeter

qcalorimeter=( mwarmwater Cwarmwater ∆ T warmwater )(mcool water C cool water ∆ T cool water)

31. Use the same two Styrofoam cups in Part B of the experiment that were used in Part A.

The calorimeter constant determined in Part A will be used in Part B of this experiment

to Determine the Molar Heat of the Dissolution of a Salt.

PART B: Determination of the Molar Heat of Dissolution of a Salt

1. You will determine the molar heat of dissolution of ammonium nitrate, calcium chloride,

lithium chloride, and potassium chloride. You will perform two trials for each salt.

2. Use a magnetic stirrer and stir bar to stir the solution

3. Nest two Styrofoam cups inside each other to prepare a Styrofoam cup calorimeter.

4. Place the calorimeter on the magnetic stirrer. Place a 1 cm stir bar inside the calorimeter.

Turn the magnetic stirrer power switch to a low setting. (When spinning, the stir bar must

not touch the temperature probe or the walls of the calorimeter).

5. Insert the MeasureNet temperature probe through the cardboard lid and place the lid-

temperature probe assembly inside the calorimeter. (Be sure the probe is placed to one

side of the calorimeter so that it does not contact the spinning stir bar).

6. Obtain 25.00 mL of distilled water. Record the exact mass of the water to 0.001

significant figures. Raise the calorimeter lid and pour the water into the calorimeter (all

of the substance must be transferred to the calorimeter). Be sure the temperature probe is

not touching the bottom or sides of the calorimeter.

7. Determine the initial temperature of the water by reading the MeasureNet screen, and

record it to 0.01 significant figures.

8. Obtain 1.00 g of the salt. Record the exact mass to 0.001 significant figures.

9. Press Start on the MeasureNet workstation to begin the thermogram. After 5-10 seconds

have elapsed, raise the calorimeter lid and quickly, but carefully, pour all of the salt into

the calorimeter.

10. When the temperature of the reaction mixture has increased or decreased and stabilized at

the equilibrium temperature, press Stop to end the scan.

11. Press File Options. Press F3 to save the scan as a tab delimited file. Enter a 3-digit code.

Press Enter to accept it. Record the file name in your Lab Report.

12. Press Display to clear the previous scan.

13. Remove the temperature probe assembly from the mixture. Remove the stir bar from the

reaction mixture with a magnetic rod. Thoroughly rinse the stir bar or copper wire stirrer

with distilled water and thoroughly dry it with a towel.

14. Decant the reaction mixture in the calorimeter into the sink, and thoroughly dry the

calorimeter.

15. Perform two trials by repeating Steps 5-14 for each of the following salts: ammonium

nitrate, calcium chloride, lithium chloride, and potassium chloride.

16. When you are finished with the experiment, transfer the files from the computer to a flash

drive, or email the files to yourself via the internet.

17. Steps 18-26 are to be completed after the laboratory period is concluded (outside of lab).

18. From the tab delimited files, prepare thermograms using Excel for each trial. Instructions

for plotting thermograms are given in Part A, Step 28, Substeps a-m.

19. Determine ΔHdissolution for each trial of each salt using the following formula:

ΔH dissolution=qdissolution

moles of the substancedissolved

qdissolution=M dissolution ×Cdissolution × ΔT dissolution

20. What is the average ΔHdissolution for each salt?

21. Based on the endothermic or exothermic dissolution processes of each salt, which should

be used for cold packs and which should be used for hot packs?

22. Use the following equation to solve # 23 and #24:

Cdissolution × M dissolution × ∆ T di ssolution

molesof substancedissolved=

Cdissolution(x+100 g water)dissolution ∆ Tdissolution

x grams of substance dissolvedg

molof substance dissolved

23. Estimate the mass of salt that must be added to a hot pack (containing 100 mL of water)

for it to reach a temperature of 65 °C if the initial temperature is 25 °C.

24. Estimate the mass of salt that must be added to a cold pack (containing 100 mL of water)

for it to reach a temperature of 0 °C if the initial temperature is 25 °C.

25. Using the current market prices given below, estimate the unit production cost per cold

pack and per hot pack.

Ammonium Nitrate $26.20 per 500 g

Calcium Chloride $31.70 per 500 g

Lithium Chloride $65.00 per 500 g

Potassium Chloride $28.19 per 500 g

Labor Cost Per Unit $0.73

Capital/Overhead Cost Per Unit $0.36

Plastic Bag Cost Per Unit $0.19

26. The production cost per pack must be less than $5.00 for the Dystan Company to return a

profit. Based on the estimated unit production costs, will the company return a profit?

Part A:Calorimeter

Data Trial 1 Trial 2Mass of Hot WaterTemperature of Hot WaterMass of Cool WaterTemperature of Cool WaterFinal Temperature

Work for Trial 1

Work for Trial 2

Average

Part B:Heat of Dissolution of Ammonium Nitrate

Data Trial 1 Trial 2Mass of Distilled Water

Initial Temperature of Distilled WaterMass of Salt

Final Temperature

Work for Trial 1

Work for Trial 2

Average

Heat of Dissolution of Calcium ChlorideData Trial 1 Trial 2

Mass of Distilled WaterInitial Temperature of Distilled Water

Mass of SaltFinal Temperature

Work for Trial 1

Work for Trial 2

Average

Heat of Dissolution of Lithium ChlorideData Trial 1 Trial 2

Mass of Distilled WaterInitial Temperature of Distilled Water

Mass of SaltFinal Temperature

Work for Trial 1

Work for Trial 2

Average

Heat of Dissolution of Potassium ChlorideData Trial 1 Trial 2

Mass of Distilled WaterInitial Temperature of Distilled Water

Mass of SaltFinal Temperature

Work for Trial 1

Work for Trial 2

Average

Bibliography:

Stanton, Bobby, Lin Zhu, and Charles H. Atwood. Experiments in General Chemistry FeaturingMeasureNet. Belmont, CA: Thomson Brooks/Cole, 2006. Print.