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Speaker 1: Welcome to Brainstuff from hose stuff works dot com where
Speaker 1: smart happens. Hi. I'm Marshall Brain with today's question, why
Speaker 1: doesn't gasoline burn cleanly? Why do we end up with
Speaker 1: things like smog and ozone that pollute disguise? Gasoline is
Speaker 1: a liquid formed almost purely of carbon and hydrogen. If
Speaker 1: you could somehow burn gasoline as a vapor with a
Speaker 1: hot flame and plenty of oxygen, you would get nearly
Speaker 1: pure carbon dioxide and water as the combustion products. That's
Speaker 1: why you can burn natural gas, LP gas and kerosene
Speaker 1: indoors in the winter, and appropriately designed kerosene heater, for example,
Speaker 1: can be ventless. Automobile exhaust, unfortunately, contains a lot more
Speaker 1: than carbon dioxide and water. The most important pollutants and
Speaker 1: car exhaust include first, carbon monoxide, which is a poison.
Speaker 1: Carbon monoxide is formed because combustion is incomplete in the cylinder,
Speaker 1: not enough oxygen is available fast enough to react completely
Speaker 1: with all the carbon available. Second is nitrogen oxides. Because
Speaker 1: of the pressure and temperature inside the cylinder, nitrogen and
Speaker 1: oxygen in the air combined in various ways, we would
Speaker 1: rather it didn't. And third is unburned hydrocarbons. Not all
Speaker 1: of the hydrocarbons participate in the reaction because there's so
Speaker 1: little time available during the combustion phase. There can also
Speaker 1: be some impurities, like sulfur in the gas to form
Speaker 1: sulfur oxides. The idea behind a kettalytic converter is to
Speaker 1: try to eliminate the carbon monoxide, nitrogen oxides, and hydrocarbons
Speaker 1: by reacting them with plenty of oxygen on a platinum catalyst. However,
Speaker 1: catalytic converters aren't perfect either, so some of the pollutants
Speaker 1: still escape. On hot summer days, we see the effect
Speaker 1: of these pollutants in the form of smog and ozone.
Speaker 1: Nitrogen oxides and hydrocarbons mixed with air and get bombarded
Speaker 1: by ultraviolet rays and sunlight. Nitrogen dioxide releases an oxygen atom,
Speaker 1: which combines with oxygen gas to form O three or
Speaker 1: ozone at ground level. Do you have any ideas or
Speaker 1: suggestions for this podcast? If so, please send me an
Speaker 1: email at podcast at how stuff works dot com. For
Speaker 1: more on this and thousands of other topics, go to
Speaker 1: how stuff works dot com and be sure to check
Speaker 1: out the brain Stuff blog on the how stuff works
Speaker 1: dot com home page. This episode of brain Stuff is
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