Question

Which one of the following is a greenhouse gas?
A. Oxygen
B. Methane
C. Sulphur Dioxide
D. Nitrogen

Answer 1

Hint: It is the simplest hydrocarbon,used worldwide as a fuel.

Complete answer:
The greenhouse effect is a naturally occurring phenomenon that is responsible for heating of the Earth’s surface and atmosphere due to the presence of certain gases like carbon dioxide, methane, nitrous oxide and fluorinated gasses such as HFCs, PFCs and sulphur hexafluoride.

So,the correct answer is (b) Methane.

Additional Information:
- Greenhouse gasses enter the Earth’s atmosphere as a result of both natural processes (such as decomposition of organic matter) and human activities(such as burning fossil fuels and agriculture).
- In the absence of the greenhouse effect, the average temperature of earth would have been a chilly -18°C rather than the present average of 15°C.
- Clouds and gases reflect about one-fourth of the incoming solar radiation and absorb some of it. But, almost half of incoming solar radiation falls on earth’s surface heating it, while a small proportion is reflected back.
- Earth’s surface re-emits heat in the form of infrared radiation but part of this does not escape into space and atmospheric gases absorb a major fraction of it.
- These gases radiate heat energy and a major part of which again comes to earth’s surface, thus heating it up once again. This cycle is repeated again and again.
- High levels of these gases in the atmosphere cause Global Warming. All these gases allow the heat waves to reach earth but prevent their escape and the earth becomes hotter.
- Chemically, a gas is considered to cause the greenhouse effect only if it is able to absorb infrared radiation from the sun. Methane (as compared to carbon dioxide) absorbs more of the infrared light (these wavelengths exhibit the most heat energy) and thus traps the most heat.
- Oxygen and nitrogen are not greenhouse gases, because they are transparent to infrared light. These molecules are invisible because when you stretch one, it doesn’t change the electric field.These are symmetric molecules, made of two identical atoms whose electric fields just cancel each other out. Neither atom can hold the electrons any more tightly than the other. In general, symmetrical molecules with only two atoms are not greenhouse gases
- Sulphur Dioxide is not a direct greenhouse gas.However, when coupled with “elemental carbon emissions,”it contributes to the formation of aerosols, which directly and indirectly affect warming and cooling in the earth’s atmosphere.

Note: An aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas, such as fog, dust, forest exudates, geyser steam, particulate air pollutants and smoke.