Specific problem
When someone gets injured, a frozen ice pack is usually applied to the injured area for approximately twenty minutes. These ice packs are not always accessible when injured. A cooler must be brought at all times to keep them frozen. Portable instant cold packs have therefore been invented as a sports medicine solution to the frozen ice pack. These packs contain ammonium nitrate and water. When these two chemicals are mixed properly, the temperature of the pack is very low which makes the pack remain cold for approximately twenty to thirty minutes. These packs are as efficient as frozen ice packs, but are however very costly.
Ammonium nitrate is a chemical that is also found in fertilizers. The percentage of ammonium nitrate is not stated on fertilizer bags because this chemical is also used to make bombs and explosives. Therefore, fertilizer companies indicate the percentage of nitrogen found in each bag. I would like to imitate the conditions of the cold pack by combining the same amount of nitrogen found in the fertilizer, as in the cold pack, with water, to create a homemade cold pack.
Description of experimental strategy
As a first step in my experiment, I will measure the amount of ammonium nitrate and water found in the portable cold pack. I will then take a second cold pack and follow directions by mixing these two chemicals. Using a thermometer, I will record the lowest temperature and its duration. As a second step, I will take the exact same number of grams of nitrogen from three different fertilizers containing different percentages of nitrogen and put it in three Ziploc bags. I will then take the exact same number of milliliters of water as found in the cold pack and put it in three smaller Ziploc bags. The bags containing water will be placed in the bags containing the fertilizers. With each of these mixtures, I will follow the same directions as on the cold pack and record the lowest temperature and its duration.
Statement of purpose
There are two purposes to this experiment. The first is to see if a homemade cold pack can be just as effective as a bought cold pack, but more cost efficient. The second purpose is to see if the temperature is affected by the amount of nitrogen in each fertilizer used.
Hypothesis
In my hypothesis I believe that a homemade cold pack is just as effective as a bought cold pack, but more cost efficient. I also believe that when the higher percentage of nitrogen in a fertilizer is mixed with water, it will produce the lowest temperature.
Variables
Independent Variable #1: In the first part of my experiment, the independent variable is the amount of ammonium nitrate or nitrogen used.
Dependent Variable #1: The dependent variable is the temperature.
Independent Variable #2: In the second part of my experiment the independent variable is the quantity of nitrogen used.
Dependent Variable #2: The dependent variable is the duration of the lowest temperature.
Literature review
When a person is injured, either, tissues will be stretched out or blood vessels will be damaged. Blood will keep flowing into the tissues until one restricts the vessels. An excess of blood into tissues will increase inflammation and must be therefore stopped before the injury can start to heal. For centuries, it has been believed that by applying ice immediately after an injury, the swelling reduces and blood will have less of a tendency to leak out. The ice should be applied for approximately 20 minutes. Other cooling materials, such as a bag of peas, have also been used instead of ice since the bag wraps itself around the injured area much better. Compression, elevation and rest, better known as “RICE”, must also follow these methods of cold therapy, also known as Cryotherapy. Other types of cold packs, such as gel packs were then created. These packs were less messy than ice packs and were also reusable. They were nevertheless expensive and still had to be kept refrigerated in order to be used properly.
In 1659, Johann R
Glauber 
was
the first person to synthesize ammonium nitrate by combining ammonium carbonate
and nitric acid. Ammonium nitrate is used today in laughing gases, freezing
mixtures, explosives and fertilizers. By combining ammonium nitrate with water
in a plastic bag, an endothermic reaction occurs, thus allowing the water to
become much colder. From these ingredients, the instant portable cold pack was
invented. This pack is costly, however, and can be used only once.
A portable instant cold pack is made up of two compartments. The first includes water and the second contains ammonium nitrate.
A thick outer bag covers these
ingredients, as shown in the diagram below. 
Ammonium nitrate is a salt, which is made up of a 50/50 mixture of ammonium and nitrate nitrogen. When ammonium nitrate is mixed with water the ammonium nitrate dissolves into the water. The energy is absorbed from the water, which causes the temperature of the water to decrease and therefore the pack becomes colder for a short period of time. This chemical reaction is better known as an endothermic reaction. The reaction can be shown using the following symbols:
NH4NO3 (s) + H2O (l) + energy NH4NO3 (aq)
where (s) represents the soluble salt, (l) represents the liquid and (aq) represents the aqueous or liquid state of the ammonium nitrate. NH4NO3 is the chemical symbol for ammonium nitrate and H2O is the chemical symbol for water. Some hot packs are made in a similar way where a salt called calcium chloride is mixed with water and releases heat, producing an exothermic reaction, thus making the pack warmer for a short period of time.
Many fertilizers also contain different percentages of ammonium nitrate. Nitrogen fertilizers are used for crop production.
The controversial issue lies in what method gives the best results in reducing a swollen injury and which of these methods is more practical, economical and keeps cooler for a longer period of time. Packs of ice or frozen vegetables are inexpensive and are often available in most homes. However, they easily fall off the injured area, the ice quickly melts, and must always be kept in a cold place such as a freezer or a cooler. These are not always accessible. Ready-made ice packs are also another means of keeping an injured area cool but are too costly and need to be kept refrigerated. When these different types of ice packs are applied to an injured area, some become warmer than others faster. Since an injured person needs to apply the pack for at least 20 minutes, the heat from the room temperature might heat up the pack faster. There are many athletes who believe that heat therapy such as a hot bath or a heating pad is the best remedy to ease the pain. Finally, many coaches today rely on an instant cold pack, which is very portable since it doesn’t need refrigeration. You can carry this cold pack with you at all times. The disadvantage is that you can only use it once and it can be costly.
Using any type of cold pack on an injury is a good means of reducing swelling, pain and tissue damage. But different cold packs have their own advantages and disadvantages. Some are expensive and some are not easily portable. Some are messy and some are not re-usable. The way of the future would be to create a homemade cold pack that is inexpensive, portable and re-usable. The homemade pack that I have created and will discuss further in this report is inexpensive, portable and environmentally friendly. After its initial use, it can then fertilize lawns or plants wasting nothing. Even the plastic Ziploc bags can be recycled for future use. It is not, however, re-usable and this could be a future challenge.