Unit 5: The atmosphere Flashcards
(53 cards)
what is air?
Air is a mixture of different gases.
What are the main gases in air, and their percentages?
Nitrogen - 78%
Oxygen - 21%
Noble gases, carbon dioxide - <1%
What are the two forces that keep the amounts of carbon dioxide and oxygen in the air constant?
Photosynthesis
– plants use up C0₂ and release oxygen
Respiration
– animals and plants use oxygen and release C0₂
For how long has the proportion of different gases in the atmosphere been the same?
For 200 million years, the proportion of different gases in the atmosphere has been the same.
What planets are believed to be similar to the earths early atmosphere?
The earths early atmosphere is believed to be similar to that on other terrestrial planets (mars and Venus) today.
What gas is believed to not have been present in the earths early atmosphere?
Scientists believe that oxygen was not present in the earths early atmosphere.
How long ago was the earth formed?
The earth was formed 4.6 billion years ago.
What do we believe the earths early surface was littered with?
Highly active volcanoes.
What do we believe caused the release of CO₂ and other gases in earths early atmosphere?
The frequent eruptions of the highly active volcanoes resulted in the release of lots of carbon dioxide (as well as smaller amounts of other gases like nitrogen).
What gas do scientists believe dominated the early atmosphere?
Carbon dioxide
How were the oceans formed?
As the earth cooled down, the oceans formed as a result of water vapour condensing.
How did nitrogen accumulate?
Nitrogen was released along with the CO₂ from volcanic eruptions, and slowly accumulated in the atmosphere.
How did the formation of the oceans cause a drop in carbon dioxide levels?
The oceans absorbed CO₂, and chemical reactions turned it into carbonates, which got locked away in rocks and sediments.
How do marine animals reduce CO₂ levels?
Marine animals use up CO₂ and remove carbonates from the oceans to construct their shells and skeletons. When they die, their shells sink to the ocean floor, trapping the carbon (in sedimentary rock).
What is photosynthesis?
Photosynthesis is the process in which light energy is used to produce glucose and oxygen from carbon dioxide and water.
What is the word and chemical equation for photosynthesis?
Carbon dioxide + water —> glucose + oxygen
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
When was oxygen first produced and by what?
Oxygen was first produced 2.7 billion years ago by algae using photosynthesis.
How did the percentage of oxygen in the atmosphere slowly increase and what did this allow
As plants evolved and more CO₂ was removed from the atmosphere, the percentage of oxygen in the atmosphere increased to a level that enabled animals to evolve.
how was CO₂ trapped due to fossil fuels?
CO₂ was trapped in the formation of fossil fuels.
. Dead plants and organisms were buried and compressed over millions of years.
. This formed coal, oil, and natural gas, storing carbon underground.
What are the three main greenhouse gases?
Carbon dioxide, methane and water vapour are the three main greenhouse gases.
How are greenhouse gases crucial to life?
Greenhouse gases trap some radiation from the sun in our atmosphere, warming the earth, and keeping it at a temperature where life can thrive.
How does the wavelength of radiation change as it goes through the atmosphere?
The sun gives of shortwave radiation, which passes easily through the atmosphere. It reaches earths surface, where it is absorbed. After absorbing this energy, the earth re-emits it as long wave radiation. Part of this long-wave radiation escapes into space, but greenhouse gases re-radiate it part of it, warming the earth up.
What is the major cause of global climate change?
The major cause of global climate change is an increase in the average global temperature.
What are the four main human activities that produce greenhouse gases?
. Burning fossil fuels
. Deforestation
. Increased agriculture
. Rubbish decomposition
