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Atmospheric Chemistry Textbookby W. R. Barron de Burgh ?Atmospheric Chemistry Specification8.18 Recall that the gases produced by volcanic activity formed the Earth’s early atmosphere8.19 Describe that the Earth’s early atmosphere was thought to contain:a little or no oxygenb a large amount of carbon dioxidec water vapourd small amounts of other gases and interpret evidence relating to this8.20 Explain how condensation of water vapour formed oceans8.21 Explain how the amount of carbon dioxide in the atmosphere was decreased when carbon dioxide dissolved as the oceans formed8.22 Explain how the growth of primitive plants used carbon dioxide and released oxygen by photosynthesis and consequently the amount of oxygen in the atmosphere gradually increased8.23 Describe the chemical test for oxygen8.24 Describe how various gases in the atmosphere, including carbon dioxide, methane and water vapour, absorb heat radiated from the Earth, subsequently releasing energy which keeps the Earth warm: this is known as the greenhouse effect8.25 Evaluate the evidence for human activity causing climate change, considering:a the correlation between the change in atmospheric carbon dioxide concentration, the consumption of fossil fuels and temperature changeb the uncertainties caused by the location where these measurements are taken and historical accuracy8.26 Describe:a the composition of today’s atmosphereb the potential effects on the climate of increased levels of carbon dioxide and methane generated by human activity, including burning fossil fuels and livestock farmingc that these effects may be mitigated: consider scale, risk and environmental implicationsThe Early Atmosphereright635000The layer of gases surrounding a planet is called the atmosphere. The Earth formed approximately 4.6 billion year ago as a molten ball of rock. There was almost no atmosphere. As the Earth cooled a solid crust formed. There was a high level of volcanic activity. Volcanoes gave out mostly carbon dioxide (CO2), steam (H2O), and small amounts of ammonia (NH3) and methane (CH4). There was little or no oxygen in the Earth’s early atmosphere. The surface was too hot for water to be a liquid. We cannot be certain of the exact composition of the Earth’s early atmosphere, however there is evidence to suggest the above.Define atmosphere.State when the earth formed.Name the gases given out by volcanoes.Describe the composition of the Earth’s early atmosphere.Explain why here were no oceans 4.6 billion years ago.The Earth’s early was mainly carbon dioxide. Identify the source of the carbon dioxide.As the Earth continued to cool steam condensed and fell as rain and the oceans formed approximately 4 billion years ago. Carbon dioxide (CO2) dissolved in the oceans. Approximately 3 billion years ago living things evolved, we’re still unsure of how, into simple photosynthetic organisms such as algae. Algae photosynthesises using up carbon dioxide and producing oxygen. Shown by the word equation:carbon dioxide + water → carbohydrate + oxygenCarbon dioxide decreased as it was taken in by plants and some of this is locked away in fossil fuels which formed from ancient plants and organisms. Another store of carbon dioxide is sedimentary rocks such as chalk and limestone both of which are made of calcium carbonate. Rocks containing iron compounds provide evidence for a changing atmosphere. Evidence of the formation of oxygen is seen in ancient rocks that contain bands of iron oxide around 3 billion years ago. In even older rocks there are other compounds of iron which can only form in the absence of oxygen, such as iron pyrite.Oxygen reacted with ammonia to produce nitrogen gas (N2) and water. The evolution of nitrifying bacteria increased the proportion of nitrogen in the atmosphere. Nitrogen is not very reactive and therefore levels of nitrogen slowly increased over time. The increase in oxygen created the ozone (O3) layer, this allowed for complex organisms to evolve.Explain when and why the oceans formed.Giving two reasons explain why the proportion of carbon dioxide in the atmosphere decreased.Suggest why scientists cannot be sure of the composition of the Earth’s early atmosphere.Describe how the composition of the Earth’s atmosphere changed due to the evolution of primitive plants.Identify evidence that suggeststhere was little or no oxygen in the Earth’s early atmosphere. the proportion of oxygen increased about 3 billion years ago.Define photosynthetic organism.Define photosynthesis.Name two stores of carbon dioxide.Explain the source of oxygen in the atmosphere.Explain the source of nitrogen in the atmosphere.Write the word equation for the reaction between ammonia and oxygen gas.Write the balanced symbol equation for the reaction between ammonia and oxygen gas.Explain why the Earth’s early atmosphere was not suitable for humans and other animals.Draw and write a storyboard for the evolution of the Earth’s atmosphere including each stage and gases present.Test for oxygen. Oxygen supports combustion. In the presence of oxygen, in a test tube for example, a glowing splint will relight.State what is meant by “a glowing splint”Describe the test for oxygen.right317500The Earth’s Atmosphere TodayThe pie chart right shows the main gases in the Earth’s atmosphere today. It has been like this for approximately 200 million years. Noble gases make up to about 1% of our atmosphere, most of this is the noble gas Argon. There is also a very small amount of carbon dioxide, just 0.04%.Copy and complete the following sentences.The two main gases in the air are ________ (__%) and ________ (__%). There is also a small amount of ______ gases (__%), mostly ______. 0.04% of the atmosphere is _______ _________.State the third most abundant gas in the Earth’s atmosphere.Extended response: Compare and contrast the early atmosphere to today’s atmosphere.Early Mars atmosphere 'oxygen-rich' before Earth's190881028638500By Paul Rincon, Science editor, BBC News website19 June 2013That is the suggestion put forward by the author of a study in Nature journal, which outlines an explanation for differences between Mars meteorites and rocks examined by a robot rover.Dr Bernard Wood said the idea fits with the picture of a planet that was once warm, wet and habitable.1842135140335Mars' atmosphere could have been rich in oxygen four billion years ago - well before Earth's air became augmented with the gas.00Mars' atmosphere could have been rich in oxygen four billion years ago - well before Earth's air became augmented with the gas.But other scientists were sceptical.While the rise of atmospheric oxygen on Earth 2.5 billion years ago was probably mediated by life, Martian oxygen could have been produced through the chemical "splitting" of water.Prof Wood and his colleagues from Oxford University looked at the chemical composition of Martian meteorites found on Earth and data from Nasa's Spirit rover, which examined surface rocks at Gusev Crater on Mars.Both are igneous rocks (of volcanic origin), but they show major geochemical differences. For example, the Gusev Crater rocks are five times richer in nickel than the meteorites. This had posed something of a puzzle, casting doubt on whether the meteorites were typical volcanic products of the Red Planet.Young and old"What we have shown is that both meteorites and surface volcanic rocks are consistent with similar origins in the deep interior of Mars, but that the surface rocks come from a more oxygen-rich environment, probably caused by recycling of oxygen-rich materials into the interior," Prof Wood explained."This result is surprising because while the meteorites are geologically 'young', around 180 million to 1.4 billion years old, the Spirit rover was analysing a very old part of Mars, more than 3.7 billion years old."Whilst the researchers conceded that large regional variations in the geological composition of Mars could not be ruled out, they argue in their paper that these differences arose via subduction - in which rocks are recycled in the planet's interior.Dr Wood, James Tuff and Jon Wade from Oxford propose that the Martian surface became "oxidised" early in its history, and that these surface rocks were drawn into the shallow interior and recycled back to the surface during volcanic eruptions around four billion years ago.The meteorites, by contrast, are much younger volcanic rocks that emerged from deeper within Mars and so were less influenced by this process.Although material can become oxidised in the presence of free oxygen gas - it is not essential for oxidation reactions to occur.But Dr Francis McCubbin, from the University of New Mexico, who was not involved with the Nature study, told BBC News: "I did not reach the conclusion that their results imply an early oxygen-rich atmosphere on Mars, only that the upper mantle was more oxidised than the deep interior, which does not actually require any oxygen gas to accomplish.""I agree with the overarching conclusions of this work that there are substantial redox gradients with depth on Mars, and this could be potentially very important for Mars' habitability because some organisms can take advantage of redox (reduction-oxidation) reactions and use them as an energy/food source.He added: "Although not implicitly stated, the early oxidized magmatism would also favour the production of water, another ingredient that is key to habitability."On alternative possibilities to atmospheric oxygen, Prof Wood told BBC News: "One is that Mars was an initially oxidised planet - that's pretty unlikely. There aren't any meteorites or other bodies in the Solar System that show this high state of oxidation."You don't need a lot of oxygen to cause this - you don't need to be at 20% concentration. It would depend on temperature and how much water was around. But you need free oxygen to do it."And the process didn't take place to any great extent on Earth at that time - which is interesting."Prof Wood explained that, as oxidation was what gave Mars its distinctive colour, it is likely that the planet was "warm, wet and rusty" billions of years before Earth's atmosphere became oxygen-rich.He added: "The principal way we would expect to get oxygen is through photolysis of water - water vapour in Mars' atmosphere interacting with radiation from the Sun breaks down to form hydrogen and oxygen."Most of that hydrogen and oxygen recombines back to water. But a small fraction of the hydrogen is energetic enough to escape from the planet. A small amount of hydrogen is lost leaving an oxygen excess."But the gravity on Mars is one third of that on Earth, so hydrogen would be lost more easily. So the oxygen build-up could be enhanced on Mars relative to Earth."QuestionsState evidence for oxygen on Mars outlined in this article.Define oxidised.Suggest two possible sources of oxygen in Mars’s atmosphereSuggest why “other scientists were sceptical” and explain why we cannot be pare the sources of oxygen in Mars’s and Earth’s atmosphere.Describe the test for oxygen.Suggest a source of Mars’s original atmosphere. State evidence that supports your suggestion.Reference: (accessed on 26/09/2019)Human ActivityHumans activity is affecting the composition of the air. The population of humans is increasing rapidly. More people means more people respiring giving out carbon dioxide. There is a greater demand for energy including heating, lighting, cooking and transport. As the world become more industrialised and affluent, there is also a greater demand for energy per person. Both the greater number and greater demand per person for energy has increased energy consumption which is provided mainly from the burning of fossil fuels which releases carbon dioxide.There is a greater demand for space for houses, crops and livestock. Space is often made available by cutting down tree (deforestation). However, plants including trees photosynthesise taking in carbon dioxide. Fewer plants and forests mean less carbon dioxide being removed from the atmosphere. Forests are also cleared for grazing. Livestock such as cattle give out methane gas. Methane is a much more potent greenhouse gas than carbon dioxide.Name three sources of carbon dioxide caused by human activity.Name one source of carbon dioxide not caused by human activity. Hint: Think or look back at the Earth’s early atmosphere.Define deforestation.Explain how deforestation increases the level of carbon dioxide in the atmosphere.Explain why a greater demand for energy increases the level of carbon dioxide in the atmosphere.Explain why a greater demand for food increases the level of both carbon dioxide and methane in the atmosphere.Name two greenhouse gasesMethane Sources - Rice Paddies43091101460500At between 50 and 100 million tonnes of methane a year, rice agriculture is a big source of atmospheric methane, possibly the biggest of man-made methane sources. The warm, waterlogged soil of rice paddies provides ideal conditions for methanogenesis, and though some of the methane produced is usually oxidized by methanotrophs in the shallow overlying water, the vast majority is released into the atmosphere. Rice is grown very widely and rates of methane emission may vary greatly between different areas. Differences in average temperature, water depth and the length of time that the rice paddy soil is waterlogged can all result in big regional variations. However, methane emission from worldwide rice agriculture has been well studied in recent years and fairly reliable estimates of global emissions now exist. Emissions from rice paddies can vary hugely during the course of a year.On average, the rice paddy soil is only fully waterlogged for about 4 months each year. For the rest of the time methanogenesis is generally much reduced and, where the soil dries out sufficiently, rice paddy soil can become a temporary sink for atmospheric methane.Human ImpactClearly, humans are directly responsible for the world's paddy fields and so also for their methane emissions. The expansion of the human population has necessitated increased rice production and so methane emission from this source. There are, though, strategies which may lessen our impact via this greenhouse gas source as outlined below.Potential for controlWith an increasing world population, reductions in rice agriculture remain largely untenable as on methane emission reduction strategy. However, through a more integrated approach to rice paddy irrigation and fertilizer application substantial reductions remain possible. Many rice varieties can be grown under much drier conditions than those traditionally employed, with big reductions on methane emission without any loss in yeild. Additionally, there is the great potential for improved varieties of rice, able to produce a much larger crop per area of rice paddy and so allow for a cut in the area of rice paddies, without a cut in rice production. Finally, the addition of compounds such as ammonium sulphate, which favour activity of other microbial groups over that of the methanogens, has proved successful under some conditions.QuestionsSummarise the link between humans and methane production as outlined in this article.Define methanogenesisExplain why rice production is unlikely to decrease.State the formula of methane.State the impact of releasing methane into the atmosphere.Methane is a greenhouse gas. Explain how methane contributes towards the greenhouse effect.Explain the effect of greenhouse gases on climate change.Suggest ways of decreasing methane emissions from rice paddy fields.Reference: (accessed 29/9/2019)Physics – Required KnowledgeElectromagnetic SpectrumSource: Electromagnetic waves are emitted, transmitted and absorbed. Transmit is when a wave passes through a medium such as air, glass, water or atmosphere. Absorb is when energy is 'taken-in' by the material and the internal energy of the material increases. Emit is when energy is ‘given-out’.Infrared radiation is radiation emitted from a hot object. These are all terms used in both physics when learning about waves and chemistry when learning about the greenhouse effect and climate change.Limelight demonstrationLimestone, calcium carbonate is heated strongly it produces lime, calcium oxide. Lime can be heated with a Bunsen burner. Infrared radiation is absorbed, and energy emitted in the form of visible light. These are two different parts of the electromagnetic spectrum and have different wavelengths.Reference: RSC In the limelight sun gives out energy at many wavelengths which the Earth absorbs. The Earth emits infrared radiation which is then absorbed by greenhouse gases in the atmosphere, warming the earth.11430-129540The Earth is not as warm as the Sun and emits infrared radiation at a longer wavelength.Some radiation is absorbed by gases in the atmosphere and radiated back to Earth. Gases which do this are called “greenhouse gases”.Some radiation is radiated into space.The Sun emits infrared, visible light and ultraviolet radiation. The Sun is very hot, and the infrared radiation emitted has a short wavelength. This is mostly transmitted through the atmosphere. Some is reflected into space00The Earth is not as warm as the Sun and emits infrared radiation at a longer wavelength.Some radiation is absorbed by gases in the atmosphere and radiated back to Earth. Gases which do this are called “greenhouse gases”.Some radiation is radiated into space.The Sun emits infrared, visible light and ultraviolet radiation. The Sun is very hot, and the infrared radiation emitted has a short wavelength. This is mostly transmitted through the atmosphere. Some is reflected into space-278130-129540The Greenhouse Effect0The Greenhouse EffectThe Earth is surrounded by the atmosphere which in turn is surrounded by empty space. The Earth’s temperature depends on the amount of heat radiation received from the Sun and the hear radiation emitted into space. Greenhouse gases, such as carbon dioxide, in Earth’s atmosphere help trap heat. A greenhouse traps heat in a similar way, hence the names greenhouse gas and the greenhouse effect. The average surface temperature of the Earth is 15oC. If there was no carbon dioxide in the atmosphere the surface temperature would be about -20oC.As the carbon dioxide in the atmosphere increases the Earth warms. The rise in temperatures coupled with changes in weather patterns is called climate change.Describe what happens to the radiation emitted by the Sun when it reaches the Earth.Explain what will happen if the Earth emits more heat radiation than it receives from the Sun.Explain what will happen if the Earth emits less heat radiation than it receives from the Sun.Describe how the radiation from the Earth is different to the radiation from the Sun.Explain what would happen to the Earth if there was no carbon dioxide in the atmosphere.Explain the link between human activity and global warming.Aug. 11, 2016NASA Climate Modeling Suggests Venus May Have Been Habitable right13970Venus may have had a shallow liquid-water ocean and habitable surface temperatures for up to 2 billion years of its early history, according to computer modeling of the planet’s ancient climate by scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York. The findings, published this week in the journal Geophysical Research Letters, were obtained with a model similar to the type used to predict future climate change on Earth.33337501088390Observations suggest Venus may have had water oceans in its distant past. A land-ocean pattern like that above was used in a climate model to show how storm clouds could have shielded ancient Venus from strong sunlight and made the planet habitable.Credits: NASA020000Observations suggest Venus may have had water oceans in its distant past. A land-ocean pattern like that above was used in a climate model to show how storm clouds could have shielded ancient Venus from strong sunlight and made the planet habitable.Credits: NASA“Many of the same tools we use to model climate change on Earth can be adapted to study climates on other planets, both past and present,” said Michael Way, a researcher at GISS and the paper’s lead author. “These results show ancient Venus may have been a very different place than it is today.” Venus today is a hellish world. It has a crushing carbon dioxide atmosphere 90 times as thick as Earth’s. There is almost no water vapor. Temperatures reach 864 degrees Fahrenheit (462 degrees Celsius) at its surface.Scientists long have theorized that Venus formed out of ingredients similar to Earth’s, but followed a different evolutionary path. Measurements by NASA’s Pioneer mission to Venus in the 1980s first suggested Venus originally may have had an ocean. However, Venus is closer to the sun than Earth and receives far more sunlight. As a result, the planet’s early ocean evaporated, water-vapor molecules were broken apart by ultraviolet radiation, and hydrogen escaped to space. With no water left on the surface, carbon dioxide built up in the atmosphere, leading to a so-called runaway greenhouse effect that created present conditions.Previous studies have shown that how fast a planet spins on its axis affects whether it has a habitable climate. A day on Venus is 117 Earth days. Until recently, it was assumed that a thick atmosphere like that of modern Venus was required for the planet to have today’s slow rotation rate. However, newer research has shown that a thin atmosphere like that of modern Earth could have produced the same result. That means an ancient Venus with an Earth-like atmosphere could have had the same rotation rate it has today.Another factor that impacts a planet’s climate is topography. The GISS team postulated ancient Venus had more dry land overall than Earth, especially in the tropics. That limits the amount of water evaporated from the oceans and, as a result, the greenhouse effect by water vapor. This type of surface appears ideal for making a planet habitable; there seems to have been enough water to support abundant life, with sufficient land to reduce the planet’s sensitivity to changes from incoming sunlight.Way and his GISS colleagues simulated conditions of a hypothetical early Venus with an atmosphere similar to Earth’s, a day as long as Venus’ current day, and a shallow ocean consistent with early data from the Pioneer spacecraft. The researchers added information about Venus’ topography from radar measurements taken by NASA’s Magellan mission in the 1990s, and filled the lowlands with water, leaving the highlands exposed as Venusian continents. The study also factored in an ancient sun that was up to 30 percent dimmer. Even so, ancient Venus still received about 40 percent more sunlight than Earth does today.“In the GISS model’s simulation, Venus’ slow spin exposes its dayside to the sun for almost two months at a time,” co-author and fellow GISS scientist Anthony Del Genio said. “This warms the surface and produces rain that creates a thick layer of clouds, which acts like an umbrella to shield the surface from much of the solar heating. The result is mean climate temperatures that are actually a few degrees cooler than Earth’s today.”The research was done as part of NASA’s Planetary Science Astrobiology program through the Nexus for Exoplanet System Science (NExSS) program, which seeks to accelerate the search for life on planets orbiting other stars, or exoplanets, by combining insights from the fields of astrophysics, planetary science, heliophysics, and Earth science. The findings have direct implications for future NASA missions, such as the Transiting Exoplanet Survey Satellite and James Webb Space Telescope, which will try to detect possible habitable planets and characterize their atmospheres.Related LinksRead the paper in Geophysical Research Letters ()NASA GISS' NExSS activities ()QuestionsExplain why Venus’s early oceans evaporated.Explain why there are no oceans on Venus today.Define habitable.Explain why there may have never been very much oxygen on Venus.Explain why one day on Venus lasts 117 days on Earth.Suggest the source of carbon dioxide in Venus’s atmosphere.Explain the evidence used to predict Venus’s early atmosphere.Name two greenhouse gases that are or were on Venus.Describe the greenhouse effect on Venus. Suggest why the description of “runaway greenhouse effect” is used.Explain and describe the similarities between Earth’s and Venus’s early pare and contrast Earth’s and Venus’s current atmospheres.Reference - (accessed 26/09/2019)Additional review tasks GraphsThe graph below is from NASA and shows atmospheric CO2 levels measured at Mauna Loa Observatory, Hawaii, in recent years, with average seasonal cycle removed.Explain what is meant by “parts per million”Calculate the percentage of carbon dioxide in the air at the beginning of 2013Describe the trend in carbon dioxide levels between 2007 and 2019The graph above only represents recent years. The graph below shows the change in carbon dioxide over thousands of years.Source: Describe the difference between the most recent peak and previous peaks on the graphExplain the cause of the rise in carbon dioxide levels in recent timesState the highest historical carbon dioxide levelCalculate the highest historical carbon dioxide level as a percentageThe graph below shows global land ocean temperature index.Describe the trend in temperatures from 1880 to 2020Explain the rise in temperatures shown in the graphThe graph below shows the average extent of the ice sheets in each September.Describe the trend in the extent of the ice sheet each SeptemberSuggest how the extent of the ice sheet will vary over a single yearUsing all the information provided in this booklet and the graphs on the this and the previous page. Explain the effects of human activity on carbon dioxide levels, global temperatures and ice sheets and how these are interconnected. ................
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