Thermochemistry
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Learning Objectives
- Define chemical potential energy.
- Give examples of chemical potential energy.
Examples
Where did gunpowder come from?
Gun powder was originally developed by the Chinese in the ninth century AD, primarily for rockets. This material is composed of charcoal, sulfur, and saltpeter (potassium nitrate). The reaction involves the conversion of the charcoal to carbon dioxide with the potassium nitrate providing the extra oxygen needed for a rapid reaction. Sulfur was included to stabilize the product, but gunpowder is still highly explosive.
Types of Energy
Two basic types of energy exist: potential energy and kinetic energy. Potential energy is stored energy. It has not yet been released, but is ready to go. Kinetic energy is energy of motion. It causes work to be done through movement.
Chemical Potential Energy
Energy is the capacity for doing work or supplying heat. When you fill your car with gasoline, you are providing it with potential energy. Chemical potential energy is the energy stored in the chemical bonds of a substance. The various chemicals that make up gasoline contain a large amount of chemical potential energy that is released when the gasoline is burned in a controlled way in the engine of the car. The release of that energy does two things. Some of the potential energy is transformed into work, which is used to move the car. At the same time, some of the potential energy is converted to heat, making the car’s engine very hot. The energy changes of a system occur as either heat or work, or some combination of both.
Figure 17.1
A dragster is able to accelerate because of the chemical potential energy of its fuel. The burning of the fuel also produces large amounts of heat.
Dynamite is another example of chemical potential energy. The major component of dynamite is nitroglycerin, a very unstable material. By mixing it with diatomaceous earth, the stability is increased and it is less likely to explode if it receives a physical shock. When ignited, the nitroglycerin explodes rapidly, releasing large amounts of nitrogen and other gases along with a massive amount of heat.
Figure 17.2
Dynamite explosion.
Key Takeaways
Summary
- Chemical potential energy is energy available in the chemical bonds of a compound.
Exercises
Practice
Questions
Read the material at the link below and answer the questions:
http://www.brighthubeducation.com/science-homework-help/118803-what-is-chemical-potential-energy/
- How is chemical potential energy released?
- Give examples of chemical potential energy.
- What is chemical potential energy dependent upon?
Exercises
Review
Questions
- What is chemical potential energy?
- How is gasoline used as kinetic energy?
- How is dynamite used as kinetic energy?
Glossary
- chemical potential energy: The energy stored in the chemical bonds of a substance.
- kinetic energy: Energy of motion.
- potential energy: Stored energy.
