Transforming Energy into Work Gasoline Engines and Steam Boilers

Gasoline, which consists largely of hydrocarbon molecules—chains of connected carbon and hydrogen atoms—acts as a fuel in an automobile engine. It

A coal-fired power plant. (©Lester Lefkowitz/Corbis. Reproduced by permission.)



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Million BTUs per person per year source: U.S. Congress, Office Technology Assessment, Energy in Developing Countries, OTA-E-486 (Washington, D.C.: U.S. Government Printing office, Jan. 19)

is a product of the distillation of raw petroleum. The energy that holds these carbon and hydrogen atoms together is stored in the bonds between each atom.

In an automobile, gasoline is mixed with air in the combustion chamber of an engine cylinder, the mixture is compressed by a piston, and a spark from the spark plug ignites the mixture. The ideal chemical reaction for this process is:

Hydrocarbons + oxygen + spark

The energy is released in the form of heat, which causes the gases to expand and pushes the piston outward. The piston is connected to a rod and a crankshaft that ultimately transform the energy locked up in molecules into the revolution of wheels, setting your car in motion. The combustion products of carbon dioxide and water are expelled through the exhaust system into the atmosphere.

Similarly, a boiler in a power plant relies on the release of energy from burning coal or natural gas to heat water and convert it into steam. The steam turns the blades of a turbine-powered generator that ultimately causes electrons to move through a wire, converting the energy from the fuel into electrical energy that can be used to power appliances in your home.

In each of these cases, energy stored in chemical bonds is transformed into useful energy that can perform work.

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