Why doesn't gasoline burn cleanly?

Since gasoline is a liquid formed of carbon and hydrogen, it's possible to trace the chemical reactions in car exhaust and understand what types of pollutants are created by a car's engine. Tune in and learn more about the science behind burning gas.

Learn more about your ad-choices at https://www.iheartpodcastnetwork.com

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:00):
Streaming TV shows and movies directly to your home is
a breeze With Netflix. As a Netflix member, you can
instantly watch TV and movies on your PC, Mac, mobile device,
or television. Get a free thirty day trial membership. Go
to Netflix dot com slash stuff and sign up today.
Welcome to Brainstuff from hose stuff works dot com where
smart happens. Hi. I'm Marshall Brain with today's question, why

(00:30):
doesn't gasoline burn cleanly? Why do we end up with
things like smog and ozone that pollute disguise? Gasoline is
a liquid formed almost purely of carbon and hydrogen. If
you could somehow burn gasoline as a vapor with a
hot flame and plenty of oxygen, you would get nearly
pure carbon dioxide and water as the combustion products. That's

(00:54):
why you can burn natural gas, LP gas and kerosene
indoors in the winter, and appropriately designed kerosene heater, for example,
can be ventless. Automobile exhaust, unfortunately, contains a lot more
than carbon dioxide and water. The most important pollutants and
car exhaust include first, carbon monoxide, which is a poison.

(01:16):
Carbon monoxide is formed because combustion is incomplete in the cylinder,
not enough oxygen is available fast enough to react completely
with all the carbon available. Second is nitrogen oxides. Because
of the pressure and temperature inside the cylinder, nitrogen and
oxygen in the air combined in various ways, we would
rather it didn't. And third is unburned hydrocarbons. Not all

(01:39):
of the hydrocarbons participate in the reaction because there's so
little time available during the combustion phase. There can also
be some impurities, like sulfur in the gas to form
sulfur oxides. The idea behind a kettalytic converter is to
try to eliminate the carbon monoxide, nitrogen oxides, and hydrocarbons
by reacting them with plenty of oxygen on a platinum catalyst. However,

(02:03):
catalytic converters aren't perfect either, so some of the pollutants
still escape. On hot summer days, we see the effect
of these pollutants in the form of smog and ozone.
Nitrogen oxides and hydrocarbons mixed with air and get bombarded
by ultraviolet rays and sunlight. Nitrogen dioxide releases an oxygen atom,
which combines with oxygen gas to form O three or

(02:26):
ozone at ground level. Do you have any ideas or
suggestions for this podcast? If so, please send me an
email at podcast at how stuff works dot com. For
more on this and thousands of other topics, go to
how stuff works dot com and be sure to check
out the brain Stuff blog on the how stuff works
dot com home page. This episode of brain Stuff is

(02:50):
brought to you by Linda dot Com. Linda dot Com
offers thousands of engaging, easy to follow video tutorials taught
by industry experts to help you learn software, creative and
business skill pills. Membership starts at twenty five dollars a
month and provides unlimited twenty four seven access tri Linda
dot Com free for seven days by visiting Linda dot
com slash brain Stuff