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Activity (Hands-On)Grades 10 - 12

Counting Calories

Photo shows a gymnasium-size piece of metal equipment with pipes, containers and controls.Figure 1. The DZero Liquid Argon Calorimeter is used to detect subatomic particles in complex quantum mechanical experiments.

The students discover the basics of heat transfer in this activity by constructing a constant pressure calorimeter to determine the heat of solution of potassium chloride in water. They first predict the amount of heat consumed by the reaction using analytical techniques. Then they calculate the specific heat of water using tabulated data, and use this information to predict the temperature change. Next, the students will design and build a calorimeter and then determine its specific heat. After determining the predicted heat lost to the device, students will test the heat of solution. The heat given off by the reaction can be calculated from the change in temperature of the water using an equation of heat transfer. They will compare this with the value they predicted with their calculations, and then finish by discussing the error and its sources, and identifying how to improve their design to minimize these errors.

Chemical engineers design and operate among other things large plants and processes that make usable products from chemicals, ranging from electrical power, food products, medicines, materials, fuels and refined chemicals. In order to safely and efficiently apply and control these processes, an engineer must know how much heat will be generated in a given reaction. If too much heat is generated, proteins denature, products burn or decompose, or a reactor might violently explode. If too little heat is generated, chemicals do not react, not enough energy is generated, or the wrong products are favored. Additionally, an engineer has to be aware of how the process equipment itself will affect the chemical process. By being able to predict how much heat will be produced in a reaction (as well as pressure), systems can be designed with specific tolerances in mind and reaction conditions maximized.

After this activity, students should be able to:

  • Describe several basic principles of thermodynamics and heat transfer in action.
  • Compare and contrast the differences between real-world application and on-paper analysis.

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