Which gas makes up about four-fifths (approximately 80 percent) of the Earth's atmosphere today?
Nitrogen
Oxygen
Carbon dioxide
Argon
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WhyNitrogen makes up about 78 percent of the modern atmosphere, while oxygen is about 21 percent.
2Multiple choice · Easy
Approximately what percentage of today's atmosphere is oxygen?
21 percent
78 percent
50 percent
4 percent
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WhyOxygen makes up about 21 percent (one-fifth) of the modern atmosphere.
3Multiple choice · Easy
Which process carried out by early plants and algae released oxygen into the atmosphere?
Photosynthesis
Respiration
Combustion
Condensation
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WhyPhotosynthesis uses CO2 and water to make glucose, releasing oxygen as a by-product.
4Multiple choice · Easy
Which of these is a greenhouse gas?
Carbon dioxide
Nitrogen
Oxygen
Argon
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WhyCarbon dioxide is a greenhouse gas that absorbs and re-radiates heat in the atmosphere.
5Multiple choice · Easy
Incomplete combustion of fuels can produce a toxic gas that reduces the blood's ability to carry oxygen. What is this gas?
Carbon monoxide
Carbon dioxide
Sulfur dioxide
Nitrogen
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WhyCarbon monoxide (CO) is a toxic, colourless, odourless gas formed by incomplete combustion that binds to haemoglobin.
6Fill in the blank · Easy
During the first billion years of Earth's history, intense volcanic activity released gases. It is thought the early atmosphere was mostly , similar to the atmospheres of Mars and Venus today.
Answer:
carbon dioxide / CO2
WhyThe early atmosphere is thought to have been mainly carbon dioxide, released by volcanoes, like the atmospheres of Mars and Venus.
7Multiple choice · Medium
How did the amount of carbon dioxide in the atmosphere decrease over millions of years?
It was absorbed by oceans and used by plants and algae in photosynthesis
It escaped from the atmosphere into space
It reacted with nitrogen to form ammonia
It was broken down by sunlight into oxygen
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WhyCO2 dissolved in the oceans and was absorbed by plants and algae during photosynthesis; carbon also became locked in sedimentary rocks and fossil fuels.
8Multiple choice · Medium
Burning fuels that contain sulfur impurities releases sulfur dioxide. What environmental problem does SO2 mainly cause?
Acid rain
The greenhouse effect
Depletion of the ozone layer
Carbon monoxide poisoning
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WhySulfur dioxide dissolves in rainwater to form acidic solutions, causing acid rain that damages buildings, trees and aquatic life.
9Multiple choice · Medium
Soot (carbon particulates) is released when fuels undergo incomplete combustion. Which problem is caused by soot?
Respiratory problems and global dimming
Acid rain
An increase in atmospheric oxygen
Reduced blood oxygen capacity
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WhySoot causes global dimming and respiratory problems, and makes buildings dirty when deposited as particulates.
10Multiple choice · Medium
Which human activity is a major source of the greenhouse gas methane (CH4)?
Cattle farming and landfill sites
Burning sulfur-rich coal
Photosynthesis by ocean algae
Erosion of sedimentary rocks
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WhyMethane is released by cattle farming (livestock digestion), rice paddies and landfill sites.
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Atmosphere: The layer of gases surrounding the Earth that is held in place by gravity.
Early atmosphere: The mixture of gases present during the first billion years of Earth's history, thought to be mainly carbon dioxide with little or no oxygen.
Volcanic activity: The eruption of volcanoes that released gases such as carbon dioxide, water vapour, nitrogen and small amounts of methane and ammonia to form the early atmosphere.
Water vapour: Gaseous water released by volcanoes that condensed as the Earth cooled to form the oceans.
Condensation: The change of a gas into a liquid as it cools, which formed the early oceans from water vapour.
Oceans: The large bodies of liquid water that formed when water vapour condensed and that dissolved much of the early carbon dioxide.
Carbon dioxide: A greenhouse gas with formula CO2 that dominated the early atmosphere and is released today by respiration and burning fossil fuels.
Dissolved carbon dioxide: CO2 from the early atmosphere that became dissolved in the oceans, reducing the amount in the air.