Extended Experimental Investigation
Cold Pack

Year 12 Chemistry

Abstract: Cold packs are based on the principle of endothermic reactions, which means a reaction that absorbs heat from the surrounding resulting in a temperature drop. Due to this temperature drop, cold packs have many benefits when it comes to injuries such as sprains and strains. It cools the local tissue and reduces bleeding, swelling and pain. It also aids in a speedy recovery. The most commonly used chemical in instant cold packs is ammonium nitrate which will be tested in the investigation along with four other chemicals in water. These other chemicals include potassium nitrate, potassium chloride, sodium acetate and sodium chloride. The
The 0.05 moles of each chemical was weighed using a glass dish, spatula and electronic scales. Breakers were then filled with 20 millilitres of water and the temperature of the water was taken. The room temperature was also recorded. The chemicals were added into separate breakers and the temperature was recorded every two minutes over a 30-minute period. After performing the tests, the two best outcomes (seen in graph 1 and table 1) were ammonium nitrate and potassium nitrate. These two chemicals were tested further by being mixed together at different ratios, including 1:1, 3:1, 1:3. The same method was used however, temperatures were recorded every two minutes over a 20-minute period and 40 millilitres of water was used instead of 20.

Calculations:
Calculations to find the weight of 0.05 moles of each chemical.
Ammonium Nitrate

Potassium Nitrate

Potassium Chloride

Sodium Chloride

Sodium Acetate

Calculating amounts of Ammonium Nitrate and Potassium Nitrate for the various ratios.
1:1 = 0.05 molar concentration of Ammonium Nitrate: 0.05 molar concentrate of Potassium Nitrate 4 grams of NH4NO3: 5.05 grams of KNO3
3:1 = 0.075 molar concentration of Ammonium Nitrate: 0.025 molar concentration of Potassium Nitrate 6 grams of NH4NO3: 2.5 grams of KNO3
1:3 = 0.025 molar concentration of Ammonium Nitrate: 0.075 molar concentration of Potassium Nitrate 2 grams