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)

absorbs the most amount of Joules 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. The equation for this reaction is H2O + NH4NO3 →NH4

+ + NO3-.

Since the ammonium nitrate undergoes an endothermic reaction, it absorbs the heat that is in the water in the form of Joules. This makes the solution cold.

BACKGROUND INFORMATION CONT.

The equation to calculate the amount of Joules absorbed by this reaction, also known as the heat of the reaction, is q=cmΔT. Q stands for the energy in JoulesC is the specific heat of the water

(4.187kJ/°C)M is the mass of the solution (10.0g-50.0g)ΔT is the change in temperature.

HYPOTHESIS

If five different amounts of ammonium nitrate (10.0g, 20.0g, 30.0g, 40.0g, and 50.0g) are dissolved in 100mL of distilled water, then the beaker containing the 50.0g will have the lowest average temperature after three trials, and therefore have absorbed the most amount of Joules.

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

Princeton university. (2010). Heat energy. Retrieved October 21, 2010, from Princeton university website: http://wordnet.princeton.edu/

Tissue, B. M. (2000). Reaction thermodynamics. Retrieved October 8, 2010, from http://www.files.chem.vt.edu/ed//.html

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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.