A car engine changes __________ energy stored in gasoline into thermal energy and then into _________ energy.
A car engine, also called an internal combustion engine, changes potential chemical energy stored in gasoline into thermal energy and then into kinetic mechanical energy.
When gasoline burns it reacts with oxygen to produce carbon dioxide and water vapor. Gasoline is a mixture of octane and similar hydrocarbons. Here's the equation of the combustion of octane:
`2 C_8H_18 + 25 O_2 -> 16 CO_2 + 18 H_2O`
We say that the gasoline contains potential chemical energy because energy is absorbed and breaks the chemical bonds in gasoline molecules then a greater amount of energy is released when new bonds are formed in H2O and CO2. The energy is released in the form of heat (thermal energy). The hot exhaust gases that are produced within the cylinder expand and exert pressure, moving the piston in the cylinder outward then inward as the gas is exhausted. Kinetic mechanical energy of the moving pistons is transferred to the drive shaft and eventually to the wheels, giving the car kinetic mechanical energy.
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