The calculation of the heat produced or consumed by a process, including a combustion reaction in the bomb calorimeter, is based on the equation C=Q/ΔT where Q is the heat produced or consumed, ΔT is the temperature changed measured by the thermometer, and C is the heat capacity of the entire system. The resulting temperature change, as measured by the thermometer, can be used to quantify the heat produced or consumed in the process. The dewar or coffee cup contains water or a solution and then heat is given off by the system (exothermic) or added to the system (endothermic) by a chemical or physical process such as a reaction, dissolving a salt, adding ice, or dropping in a hot piece of metal. The calorimetric experiments performed with the dewar and coffee cup operate in a similar manner. Consequently, most instructional laboratories use a coffee cup for the calorimetric experiments instead. The dewar has superior insulating characteristics over the coffee cup but is relatively expensive. The dewar is a double-walled glass vessel with an insulating vacuum in between. Both of these are insulating vessels that operate equivalently by reducing the flow of heat into and out of the calorimeter. The other two calorimeters are a dewar and a Styrofoam coffee cup. Because of the large mass of the bomb and water, it will take at least five minutes before a steady state is achieved. The heat of combustion of the sample is measured by igniting the sample and then measuring the resulting temperature change. The assembled bomb is then placed in a bucket of water with approximately 2 L of water, and the bomb is pressurized with approximately 30 atm of O 2. The bomb is assembled by placing the bomb head in the bomb and then sealing the bomb with the screw cap. An ignition wire, roughly 4 cm long, is placed between the two posts and feeds down near the sample. A small cup that holds the sample rests on the bomb head. The first is a bomb or combustion calorimeter that is a stainless steel container consisting of the "bomb", the bomb head, and a screw cap. Three calorimeters are provided in the simulation. These results can then be used to validate Hess's law demonstrate the interplay between enthalpy, entropy, and Gibb's free energy calculate heats of formation from heats of combustion and study the effects of dissolved solutes on the boiling point and freezing point. From these measurements, students will be able to measure heats of combustion, heats of solution, heats of fusion, heat capacity, boiling point elevation, and freezing point depression. The focus in the calorimetry simulation is to allow students to measure the heat effects of various chemical and physical processes using equipment that can be found in most instructional laboratories and some equipment that would be less readily available. In Virtual ChemLab: Calorimetry, experiments are performed in a framework consistent with the other Virtual ChemLab simulations that is, students are put into a virtual environment where they are free to choose their reagents and equipment, build a conceptual experiment of their own design, and then experience the resulting consequences. The primary purpose of the calorimetry simulation is to provide students a realistic environment where they can explore and better understand the concepts in chemical thermodynamics using fundamental calorimetric methods.
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