You can record at longer intervals, such as 30 sec, if you choose.Record the temperature every 15 seconds (sec) until it stabilizes. Stir the contents with a plastic spoon.Add 10.0 g of ammonium nitrate to the water in cup #1.Point the digital thermometer at the water's surface and push the "on" button to get the temperature.Record the starting temperature of the water in cup #1 in a data table in your lab notebook. Use a plastic spoon to add 10.0 g of ammonium nitrate on the square/weigh boat.Place one of the wax paper squares on the scale.Ammonium nitrate from an instant cold pack. Newspaper, scrap to cover your work surfaceĭigital scale, accurate to at least 1 g, such as the digital pocket scale fromįigure 1.Weigh boats or wax paper, cut into 10-cm squares (15, more as needed) used as a surface for weighing out the ammonium nitrate crystals.The water is in a separate bag within the cold pack. Instant cold packs are available at most sporting goods stores. Instant cold packs containing ammonium nitrate and water (4).Graduated cylinder, 100mL or metric measuring cup, liquid, with 100mL mark.Flash Tutorial: Ammonium Nitrate Dissolution. This more-advanced site discusses the thermodynamics of the ammonium nitrate reaction. Based on your research, what is the definition of entropy? Does it increase or decrease when ammonium nitrate dissolves in water?.How does the heat capacity of water compare with the heat capacity of other common materials, such as aluminum, glass, or air?.What is the chemical formula for ammonium nitrate dissolving in water?.Based on your research, what are some examples of exothermic and endothermic reactions?.In the procedure, you will dissolve different amounts of ammonium nitrate in water and measure the before and after temperatures, then graph the temperature change vs. In this chemistry science fair project, you will determine how the amount of ammonium nitrate that is dissolved in water affects the magnitude of the temperature change that occurs. Substances other than water have different heat capacities. c = heat capacity, measured in joules per gram per degrees Celsius, (J/g☌)Įquation 2 says that "the heat capacity of water is 4.18 joules per gram of water per degree Celsius." What this means is that if you add 4.18 J of heat energy to 1 g of water, its temperature will increase by 1.0☌.How much heat energy is "lost" when ammonium nitrate dissolves in water? You can measure the amount of heat that is involved using Equation 1.
In the process of dissolving the crystal, the water molecules "donate" some of their energy.
When it is dissolved in water, it splits into positive ammonium ions and negative nitrate ions. Ammonium nitrate is a white crystalline substance. Many instant cold packs contain ammonium nitrate. The cold pack starts to cool as soon as the inner bag is broken, and stays cold for over an hour. When the cold pack is squeezed, the inner bag of water breaks and the water mixes with the chemicals.
These cold packs have a strong outer plastic layer that holds a bag of water and a chemical, or mixture of chemicals, that result in an endothermic reaction when dissolved in water. This kind of endothermic process is used in instant cold packs. As an example of an endothermic reaction, when the chemical ammonium nitrate is dissolved in water, the resulting solution is colder than either of the starting materials. Reactions that are accompanied by the absorption of heat are called endothermic. The burning of gasoline in a car engine is an example of an exothermic reaction. Chemical reactions that produce heat are called exothermic. Have you ever used a hot pack to warm your hands or a cold pack on an injury? How can something produce heat or cold without any microwaving or refrigeration involved? The answer is: chemistry.