Lab 12 Formal Lab Report.docx

Dystan Medical Supply Company Cold Packs and Hot Packs Sylvia Xi Section #1030 3/1/19

Introduction Cold and hot packs are an important part of everyday life. When dealing with injuries, cold and hot packs are both used, serving as quick simple remedies to help speed up the healing process. For instance, cold packs can be applied to injuries to reduce inflammation (sprained ankles). 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. On the other hand, hot packs work in the opposite way. Heat flows from the pack to the injury, increasing the the blood flow and allowing more oxygen to reach the injured area and speed healing. Hot packs help to reduce muscle spasm, soreness, and aches. 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. The coldness or hotness of the packs depends on the concentration of the salt. Cold packs absorb heat due to the endothermic reaction between the salt and the water, whereas the hot packs releases heat energy due to the exothermic reaction, and the amount of heat depends on the concentration of salt. So, a pack that feels cold will contain an endothermic reaction inside of it, and 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 (cold pack) or exothermic (hot pack) reaction occurs. The company has confirmed that each pack will contain 100 mL of water. We have to determine how much salt(mass) is required to produce a 100-mL cold pack that will reach 0°C and how much salt(mass) is required to produce a 100-mL

hot pack that will reach 65°C . Both the packs can be stored at 25°C. 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. The first part of the experiment will be to determine the calorimeter constant by using two Styrofoam cups and a lid. A temperature probe will be put through the hole in the lid, and two trials will be conducted to find the calorimeter constant and averaged. Each trial will have a graph to find the stabilizing temperature from the thermogram.

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:

Calculation for Calorimeter Constant q calorimeter = -(m warm water * C warmwater * ΔT warmwater)- (m cool water * C cool water * ΔT cool water) C calorimeter= q calorimeter/ ∆ T water 

q calorimeter = the heat absorbed by the calorimeter



C calorimeter = calorimeter constant (J/ deg C)



∆ T water = change in temperature of 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 deltaH will be an exothermic reaction; this would go in a hot pack



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

∆Hdissolution =qdissolutionmoles of substance dissolved In the second part of this experiment, the team will measure the enthalpy of the dissolution of each salt using two Styrofoam cups constructing a calorimeter. Two trials will be performed for each salt, and the average molar heat of dissolution will be calculated as the final molar heat for the given salt. A thermogram will be recorded and graphed to find the stabilizing temperature of each salt. From our findings, we will be able to conclude whether the enthalpy is exothermic or endothermic. An exothermic reaction between a salt and water produces a hot pack because the heat released will raise the temperature of the contents. An endothermic reaction will produce a cold pack because the heat will be absorbed thus lower the temperature in the pack. To determine the unit production cost, we will base it on the mass we found in out previous steps in order to determine if the company will make a profit per pack.

Final objective: To determine which ionic compounds(salts) are best suited for the production of cold packs and which are best suited for hot packs. From there we will then determine the unit cost of production per cold pack and hot pack- seeing if the company will make a profit from the packs.

Materials 1. MeasureNet: A system that allows one to collect data (i.e- temperature, pH, enthalpy change, etc.) 2. MeasureNet temperature probe: Device used to measure temperature of substances 3. Ring Stand: Used to mount Ring Clamp so probe can be used 4. Ring Clamp: Used to securely hold probe in place 5. Rubber Stopper: Used to securely hold probe in place 6. 2 Styrofoam Cups: One nested inside the other to form Calorimeter 7. Lid: Placed on top of calorimeter to make sure no solution escapes 8. Hot Plate: Device used to heat up water 9. Beaker: Device used to hold substances (i.e.- hot water) 10. Graduated Cylinder: Device used to accurately measure volume (and thus mass) of water used 11. Mass Scale: Device used to measure mass of substances/materials 12. Magnetic stirrer: Device used to stir substances (stir bar magnetizes to stirrer to mix solution) 13. Stir Bar: Small magnetic bar used to mix together cold/hot water or cold/salt together 14. Small Beaker: Device used to hold salt when measuring out on scale 15. Rubber Gloves: Device used to help securely handle hot water 16. Thermometer: Device used to measure temperature

Reagents

4 salts in total: *determine if salt is used for hot or cold pack

1.

Ammonium nitrate

2.

Calcium chloride

3.

Lithium chloride

4.

Potassium chloride

Experimental Procedure 1. On the measurenet, I pressed On > Main Menu > F2 > F1 2. I half-filled a beaker with ice and water to calibrate the temp probe. 3. I pressed Calibrate > 0.0°C > Enter > stir probe in ice water until reaches 0.0°C >Enter 4. I then removed the temp probe. I pressed SetUp > F1 (arrow keys for min/max shown) a. X-axis: time / I set min: 0 seconds, max: 250 seconds > Enter b. Y-axis: temperature / I set min 15°C, max: 75°C > Enter 5. Press Display

Part A: Determining the Calorimeter Constant

1. I made sure I had all my materials ready: Ring Stand with utility clamp on, and rubber stopper in the clamp, temp probe secured in rubber stopper 2. Below the ring stand, I put down my magnetic stir plate

3. Before all else, I grabbed a 150-mL beaker and filled it halfway full with water. I put this beaker onto a hot plate, and heated it on the highest setting. Wait for water to boil until temp is 70-80 ºC. 4. To make the calorimeter, I nested one styrofoam cup inside another styrofoam cup, and placed the magnetic stir bar inside. 5. I then measured out 50g of water inside the graduated cylinder, writing it down (cold water mass). I poured this into my styrofoam cups. 6. Now I turned on the stir bar. 7. WORK QUICKLY/CAREFULLY: When the hot water has reached 70-80 ºC, I used the rubber gloves and poured 50mL into a separate graduated cylinder than the one that was used for the cold water. I wrote this down and used a thermometer to take the temperature (hot water mass/ initial temp) 8. With the measurenet setup ready, I pressed Start. 9. Waiting 5-10 seconds, I then poured in my hot water. 10. I let the cold and hot water stir together and watched the measurenet to see a change in the line. Once the line has leveled out, I waited a few more seconds then pressed Stop. 11. Then press File Options > F3 to save > 3 digit number >Display for next trial 12. I then repeated this for a 2nd trial (take the two trials average calorimeter constant)

Part B: Determining the molar heat of dissolution for each of the sample salts.

Need to record/write down:

- Mass of salt

- Mass of water

- Initial/Final Temp: Get from emailed graph

1. I used the same calorimeter setup in the first part of the experiment. 2. I obtained 2.000 grams each of ammonium nitrate, calcium chloride, lithium chloride, and potassium chloride, Recording the exact mass of each of the salts to three decimal places (0.001g). I used the mass scale to measure it, and the beaker to hold it. 3. First, I started off with the Ammonium Nitrate. 4. I obtained 50.0 g of distilled water, recorded this- poured it into the styrofoam cups. 5. I turned on the stir bar. 6. With measurent setup, I pressed start, waited 5-10 seconds, then dumped in the salt into the water. 7. I waited for the graph to change then once it leveled out, I waited a few seconds then pressed stop. 8. Then press File Options > F3 to save > 3 digit number >Display for next trial 9. I then repeated this for a 2nd trial for the ammonium nitrate 10. I repeated this process for all three other salts (2 trials each) 11. In total, I had 2 trials for the calorimeter constant, and 8 trials for the 4 salts.

Results Part A: Determining Calorimeter Constant Trial 1 Mass of Water

Initial Temperature

Final Temperature

Hot Water

50mL

77.01°C

45.22°C

Cold Water

50mL

21.07°C

45.22°C

Trial 2

Mass of Water

Initial Temperature

Final Temperature

Hot Water

50mL

79.0°C

48.13°C

Cold Water

50mL

22.83°C

48.13°C

Part B: Determining Molar Heat Dissolution of each Salt

Trial 1

Substance

Mass (g)

Mass of Water

Initial Temperature Final Temperature (°C) (°C)

Ammonium Nitrate

2.036

49.8

22.85

19.87

2.048

50.0

22.62

19.61

2.040

50.0

22.72

20.45

2.089

50.0

22.52

20.16

22.51

30.14

Trial 2 Trial 1

Potassium Chloride

Trial 2 Trial 1

Lithium Chloride

Trial 2 Trial 1 Trial 2

Calcium Chloride

2.000 2.002

50.0

22.65

30.05

1.955

50.0

22.57

27.41

2.175

50.0

22.47

27.55

Graphs

Temperature(°C)

Calorimeter Constant Trial 1 50 45 40 35 30 25 20 15 10 5 0 0

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Calorimeter Constant Trial 2 60

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Ammonium Nitrate Trial 1 50 45 40 35 30 25 20 15 10 5 0

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Potassium Chloride Trial 1 50 45 40 35 30 25 20 15 10 5 0

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Potassium Chloride Trial 2 50 45 40 35 30 25 20 15 10 5 0 0

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Lithium Chloride Trial 1 50 45 40 35 30 25 20 15 10 5 0

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Lithium Chloride Trial 2 50 45 40 35 30 25 20 15 10 5 0 0

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Calcium Chloride Trial 1 50 45 40 35 30 25 20 15 10 5 0

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ANSWER / BEST SALT FOR COLD AND HOT PACKS

Hot Pack: Lithium Chloride (LiCl) was the best choice. It had the most desirable results at a cost of $2.50 per bad opposed to $2.62 per bag using CaCl2. Both salts achieved the desired exothermic reaction but the LiCl was more cost effective than the CaCl2.

Cold Pack: Potassium Chloride (KCl) was the best choice. It had the most desirable results at a cost of $3.06 per bad opposed to $3.56 per bag using Ammonium Nitrate (NH3Cl). Both salts achieved the desired exothermic reaction but the KCl was more cost effective than the NH3Cl.

Conclusion As shown in my calculations above, the Lithium Chloride (LiCl) was chosen as the best hot pack option and the Potassium Chloride (KCl) was chosen as the best cold pack option because of the salts effectiveness and price point. Both were found to be the most effective due to the lower change in enthalpy. Though the Ammonium Nitrate (NH3Cl) was also an effective cold pack salt, it wasn’t as cheap as the KCl. Same went for the Calcium Chloride (CaCl2) for the hot packs. The best salt for each pack was determined on not only efficiency and actual effectiveness of the salt, but also the price.

Experimental Errors: Though my partner and I tried to be the most accurate and precise as possible, there are still possible errors that could have suggested changes in the experiment. One such example is when pouring in the hot water into the graduated cylinder, measuring the temperature, and then pouring it into the styrofoam cups in the first part of the experiment for the calculation of the calorimeter constant. The hot water could have cooled down after we took the temperature of it. Since we need to carefully pour the hot water into the styrofoam cups, the time taken in between may have cooled down the water and made our measurements not as precise. Some other factors that could have led to experimental error would be excess water present in the styrofoam cups before doing the second trial or incorrect temperature and mass measurements. But these are

highly unlikely to have affected the experiment since my partner and I made sure to keep the cups as clean and dry as possible in between trials, and made sure to write down the most exact measurements possible.

Summary Through this lab, I found out which salts were the best to use for hot and cold packs. By both cost and effectiveness, I was able to determine KCl as the best cold pack salt and LiCl as the best hot pack salt. To determine which salts were suitable for the hot packs, I determined if the salt resulted in an exothermic reaction, and for cold packs determined if it resulted in an endothermic reaction. This experiment consisted of first finding a calorimeter constant using hot and cold water. We then poured various salts into the calorimeter as well as water to calculate the heats of dissolution. Once these were found, the mass and then the cost could then be calculated. The most important results of this experiment were that ammonium nitrate was the most efficient and cost-effective salt for the cold packs, while Lithium chloride is that for the hot packs. I learned that every salt from Dystan Medical Company will still return a profit, regardless of their hot and cold abilities.

Bibliography https://www.healthline.com/health/chronic-pain/treating-pain-with-heat-and-cold#cold-therapy

https://consumer.healthday.com/encyclopedia/first-aid-and-emergencies-20/emergencies-and-first-aidnews-227/ice-and-heat-packs-645144.html