chemistry

Experiment 2Cold Packs Vs. Hand-Warmers

Experiment Inventory

Materials 1/4 Contents of a Cold Pack (ammonium nitrate,

(NH4NO3)

Entire Contents of a Hand Warmer

*Graphing Software

*Computer / Internet Access

*Paper Towels

*Distilled Water

Labware 2 Calorimeters (Styrofoam™ Cups)

10 mL Graduated Cylinder

Scale

Stir Rod

Spatula

Thermometer

Weigh Boat

*Scissors

*Stopwatch / Clock Note: You must provide the materials listed in *red.

EXPERIMENT 2: COLD PACKS VS. HAND-WARMERS In this experiment, you will observe the kinetic energy of molecules by comparing the temperature changes in a calorimeter. Specifically, you will observe the temperature changes for cold packs and hand warmers. Since temperature is defined as the average kinetic energy of the molecules, changes in temperature indicate changes in energy. You will use a Styrofoam™ cup as a calorimeter to capture the energy. The lid will not be placed on the cup since ample oxygen from the air is needed for the hand warmer ingredients to react within a reasonable amount of time.

PROCEDURE

Part 1: Cold Pack

1. Put on your safety glasses and gloves (provided in your safety box).

2. Measure 10 mL of distilled water into a 10 mL graduated cylinder.

3. Turn on the scale by pressing the button labeled “0/T.”

4. Place the weigh boat on the scale and press the 0/T button a second time to zero the scale. Make sure that the units are in grams (g). If not, press the M button until the units displayed are in grams.

5. Using your scissors, cut off the top of your cold pack and weigh out 10 g of the ammonium nitrate (NH4NO3) crystals found in the inner contents of the pack.

6. Place the 10 g of the ammonium nitrate into a Styrofoam® cup. The Styrofoam® cup will be used as a calorimeter.

7. Place a thermometer and a stir rod into the calorimeter (Styrofoam® cup).

8. Pour the 10 mL of distilled water into the calorimeter containing the ammonium nitrate (NH4NO3) taken from the cold pack.

9. Immediately record the temperature and time in Table 4.

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10. Quickly begin stirring the contents in the calorimeter.

11. Use your stopwatch or timer to record the temperature at 30 second intervals in Table 4. You will need to stir the reaction the entire time you are recording data.

12. Collect data for at least five minutes, or until the temperature reaches its minimum and begins to rise. This should take approximately five to seven minutes.

13. Record the overall minimum temperature in the appropriate place in Table 4.

Part 2: Hand Warmer

Hint: The iron within the hand warmer mixes with the oxygen in the air and oxidizes in a process known as an oxidation reaction:

1. Wash the thermometer and dry it with paper towels. Remember to rinse it with distilled water before drying. Carefully place the thermometer in the other Styrofoam® cup.

2. Cut open the inner package of the hand warmer and quickly transfer all of its contents into the calorimeter.

3. Immediately record the initial temperature of the contents and begin timing the reaction.

Hint: Data collection should start quickly after the package is opened, because the reaction will be activated as soon as it is exposed to air.

4. Begin stirring the contents in the calorimeter with your thermometer.

5. Continue stirring, recording the temperature at thirty second intervals in Table 5. You will need to stir the reaction at a consistent rate the entire time you are recording data.

6. Set a stopwatch or timer for five minutes. Let the reaction continue for at least five minutes, or until the temperature has reached its maximum and then fallen a few degrees. This should take approximately 5 to 7 minutes.

7. Record the overall maximum temperature in the appropriate place in data Table 5.

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Data Sheet Experiment 2 Data Sheet

Table 4: Cold Pack Data

Time (sec) Temperature (°C)

Initial

30

60

90

120

150

180

210

240

270

300

330

360

390

420

450

Minimum Temperature(°C)

Table 5: Hand Warmer Data

Time (sec) Temperature (°C)

Initial

30

60

90

120

150

180

210

240

270

300

330

360

390

420

450

Maximum Temperature (°C)

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