COLD PACK CHEMISTRYCaroline Manion

PROBLEM AND QUESTION

What happens when instant cold packs are activated?

The purpose of this experiment was to discover which amount of ammonium nitrate (NH4NO3) becomes the coldest when dissolved in

100 mL of water.

BACKGROUND INFORMATION

Ammonium Nitrate (NH4NO3 ) is a solid, odorless, colorless crystalline salt used in fertilizers and explosives.

When combined with water, NH4NO3

undergoes an endothermic reaction, absorbing the heat in the solution.

HYPOTHESIS

If five different amounts of ammonium nitrate (10.0g, 20.0g, 30.0g, 40.0g, and 50.0g), the beaker containing the 50.0g will have the lowest average temperature after three trials.

MATERIALS

5 Beakers Distilled water (100mL per beaker) Ammonium Nitrate (NH4NO3 ) Temperature Probe Stirring Rod

PROCEDURE

1. A beaker was filled with 100mL of distilled water. The starting temperature of the water was taken and recorded

2. 10.0g of NH4NO3 were measured and added to the water.

3. The solution was stirred and the temperature taken after 30 seconds.

4. Steps 1-3 were repeated for 20.0g. 30.0g, 40.0g, and 50.0g of NH4NO3 .

5. Steps 1-4 were repeated for 2 more trials of each amount.

VARIABLES

IndependentAmount of NH4NO3

DependentTemperature of water after 30 seconds

ConstantAmount of waterAmount of time the solution sat for (30 s)

DATAAverages Beaker 1 Beaker 2 Beaker 3 Beaker 4 Beaker 5

Initial Temp. of

Water

19.5° C 19.5° C 19.8° C 21.0° C 20.9° C

Temp. After 30

seconds

13.4° C 8.4° C 5.2° C 2.9° C 0.5° C

Beaker 1 Beaker 2 Beaker 3 Beaker 4 Beaker 5

Heat of Reaction -255 -930 -1800 -3000 -4000

DATA

DATA

CONCLUSION

The Hypothesis was supported because beaker 5, which contained 50.0g of NH4NO3 was the coldest after 30 seconds.

Some sources of error were that only 3 trials were conducted due to a limited supply of NH4NO3 and instances where the software to record the temperature was not started right away.

Further research would include more trials and to discover at which amount of NH4NO3 the heat of the reaction no longer follows a linear trend.

THANK YOU!References Ammonium nitrate. (n.d.). Retrieved October 8, 2010, from Houghton Mifflin Company

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Ammonium nitrate. Retrieved October 5, 2010, from New World Encyclopedia website: http://www.newworldencyclopedia.org//_nitrate

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Wilbraham, A. C., Staley, D. D., Matta, M. S., & Waterman, E. L. (2008). Heat of solution. In Chemistry (p. 525). Upper Saddle River, NJ: Pearson Prentice Hall.