Video Transcript
Which of the following gases is not
classified as a greenhouse gas? (A) Carbon dioxide, (B)
chlorofluorocarbon, (C) methane, (D) nitrogen, (E) water vapor.
A greenhouse gas is a gas found in
the Earth’s atmosphere that absorbs infrared radiation, causing the atmosphere to
heat up. The heating of the atmosphere
happens when shorter-wavelength radiation from the Sun passes through the atmosphere
and heats the Earth. The warmed surface of the Earth
emits infrared radiation of a longer wavelength. A lot of this infrared radiation
passes out into space. Some of the infrared radiation is
absorbed by greenhouse gases in the atmosphere, which causes a heating effect.
There are many gas molecules that
can absorb infrared radiation in this way that are potential greenhouse gases. The main greenhouse gases present
in our atmosphere are water vapor, carbon dioxide, and methane. Water vapor is produced naturally
when water from the seas and oceans evaporates. Carbon dioxide enters the
atmosphere when fossil fuels are burned to release energy. Methane can seep from the ground
where oil and decaying matter are buried and then enter the atmosphere. Since water vapor, carbon dioxide,
and methane are the main greenhouse gases in our atmosphere, they are not correct
answers in this question.
Other greenhouse gases exist in our
atmosphere, but they are present in much smaller amounts. Chlorofluorocarbons, or CFCs, are
found in some refrigerators and air-conditioning systems, where things are kept
cool. They are potent greenhouse
gases. In most countries, the use of CFCs
in refrigerators is no longer permitted. Since chlorofluorocarbons, or CFCs,
are potent greenhouse gases, chlorofluorocarbon is not the correct answer in this
question.
Nitrogen gas makes up approximately
78 percent of the Earth’s atmosphere. Nitrogen is not classed as a
greenhouse gas as it does not absorb infrared radiation. Nitrogen gas is not responsible for
any heating of our atmosphere in this way. Therefore, the gas not classified
as a greenhouse gas is answer choice (D), nitrogen.
