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How do I make an ammonium nitrate cold pack?

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Quick Answer

It is possible to make an ammonium nitrate cold pack at home by mixing ammonium nitrate with water. In addition to ammonium nitrate, the project also requires a plastic bag, a glass, safety equipment and a stirring implement, such as a spoon.

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Full Answer

Ammonium nitrate cold packs are popular for treating sports, camping and schoolyard injuries because they are portable and require no refrigeration. Ammonium nitrate cold packs are available in most stores, but it is possible to make one at home using a few ingredients. Ammonium nitrate is a white, granular substance that is mainly used in fertilizer. It is available as a pure chemical, but is difficult to obtain in large quantities, since it is a semi-controlled substance sometimes used in explosives.

When making a cold pack at home, observe proper safety precautions. Ammonium nitrate is a hazardous chemical and should not come into contact with skin or eyes. First, place ammonium nitrate and water in a glass and stir with a spoon until the ammonium nitrate dissolves, and then pour the mixture into a plastic bag and seal. Use a heavyweight bag with a dependable closure to avoid leaks. Dissolving ammonium nitrate in water causes an endothermic reaction as the water molecules lose some of their heat energy, which results in cooler water. The greater the amount of ammonium nitrate added, the colder the water will become. Generally, the cold pack will fall to around 35 degrees Fahrenheit and remain at that temperature for 10 to 15 minutes.

To make the homemade cold pack portable, place a small amount of ammonium nitrate in a small bag or breakable tube and place this inside the larger bag with water. When needed, break the tube inside the larger bag to trigger the reaction.

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