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How do cars run?
The burning of fuel in an automobile engine is a chemical reaction. We normally refer to this chemical reaction as combustion. Automobile fuels are made up mostly of two elements hydrogen and carbon. These are therefore called hydrocarbons.
 During complete combustion in the engine, these two elements unite with a third element, the gas oxygen. Each oxygen atom connects up with two hydrogen atoms to form water. Each carbon atom connects up with two oxygen atoms to produce the gas carbon dioxide.
During combustion of gasoline in the engine, the burning gases get very hot. Their temperatures may go as high as 33190C. This high temperature produces the pressure that makes the engine run and produce power. Some of the gasoline does not burn. Also some only partly burns producing carbon monoxide. The unburned gasoline and partly burned gasoline cause pollution of the air as they exit through the tail pipe with the exhaust gases. The metal in an engine piston, expands and gets larger as its temperature increases. First a mixture of air and gasoline vapor is taken into the cylinder. Then the piston moves up to compress this mixture. Compressing the mixture - increasing the pressure on the mixture - makes it hot. Next, the compressed mixture is ignited, or set on fire. It burns producing a very high temperature. The high temperature causes high pressure. The high pressure pushes the piston down. This motion is carried to the car wheels so that they turn and the car moves.


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