chem of the atmosphere Flashcards
(34 cards)
Proportion of different gases in the atmosphere
For 200 million years, the proportions of different gases in the atmosphere have been much the same as they are today:
21% oxygen
78% nitrogen
0.9% argon
0.04% carbon dioxide
<0.1% other substances
Old composition of the atmosphere
a large amount of carbon dioxide
little or no oxygen
small amounts of other gases, such as ammonia and methane
similar to mars or venus today
Theory of earth’s early atmosphere and why is it limited
Theories about what was in the Earth’s early atmosphere and how
the atmosphere was formed have changed and developed over
time. Evidence for the early atmosphere is limited because of the
time scale of 4.6 billion years.
One theory of earth’s early atmosphere you should know about
One theory suggests that during the first billion years of the Earth’s existence there was intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form the oceans. (4500 million years ago) At the start of this period the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas.
Volcanoes also produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia.
When the oceans formed carbon dioxide dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere. No knowledge of other
theories is required.
Around 3.4 billion years ago first life started on Earth, that didn’t ened oxygen to survive.
Around 2.7 billion years ago first algae formed - photosynthesis.
How oxygen increased in the atmosphere
Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis, which can be represented by the equation:
6CO2 + 6H2O –> C6H12O6 + 6O2
carbon dioxide + water – light –> glucose + oxygen
Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere. Over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve.
How carbon dioxide decreased in the atmosphere
Algae and plants decreased the percentage of carbon dioxide in the
atmosphere by photosynthesis.
Carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon.
What are greenhouse gases? give 3 examples
Greenhouse gases in the atmosphere maintain temperatures on
Earth high enough to support life. Water vapour, carbon dioxide and
methane are greenhouse gases.
Greenhouse effect
Earth is heated by the sun
The greenhouse gases let short-wavelength radiation pass through the atmosphere to the Earth’s surface
The surface of the EArth cools down by emitting longer wavelenght infrared radiation
However, greenhouse gases absorbe infrared radiation.
The hihger proportion of greenhouse gases in the air, the more energy is absorbed so some of the energy radiation from the surface of the earth gets trapped in the atmosphere and hte temperature rises.
Some energy radiated back into space, greenhouse gases absorb some energy and reflect it back ot earth
Two human activities that increase the amount of carbon dioxide in atmospehre
burning fossil fuels in vehicles and power stations releases carbon dioxide
deforestation releases carbon dioxide and reduces the absorption of carbon dioxide through photosynthesis
Two human activities that increase the amount of methane in atmospehre
farming cattle releases methane
farming rice in paddy fields releases methane
how will human activities result in global climate change
Based on peer-reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth’s
atmosphere to increase at the surface and that this will result in global climate change.
Why is it difficult to model such complex systems like global climate change.
However, it is difficult to model such complex systems as global climate change. This leads to simplified models, speculation and opinions presented in the media that may be based on only parts of
the evidence and which may be biased.
Climate science is complicated and it is difficult to predict and explain what will happen to global temperatures in the future.
When evaluating the quality of evidence on an issue like global warming, you should consider:
who did the research and whether they are trustworthy, skilled and experienced
who funded the research, because that might cause some bias
what methods were used to collect and analyse the data, because that might cause uncertainties in the evidence base
which organisation is reporting or publishing the evidence
An increase in average global temperature is a major cause of climate change.
There are several potential effects of global climate change - name some
The effects of global warming include:
glaciers and polar ice melting
sea levels rising
patterns of rainfall changing, producing
floods or droughts
habitats changing
discuss the scale, risk and environmental implications of
global climate change.
Climate versus weather
Climate is different from weather because climate refers to the average temperature and cycles of weather over long periods of time - decades at least. You might talk about the weather being windy last week, or hotter last year than the year before. But unless you compare data for many years you cannot make a judgment about whether the climate is changing.
Climate change
The Earth’s climate has been constantly changing since the Earth was formed 4.6 billion years ago. This includes several
ice ages and periods of much warmer global temperatures. Until 200 years ago, these changes were all caused by natural changes such as volcanic eruptions and changes in the energy that reaches the Earth from the Sun.
Global warming
Global warming is not the same as
climate change. Global warming is usually used to describe the warming of the climate in the past 200 years, which the vast majority of scientists are almost certain has been caused by human activities.
The correlation between carbon dioxide and global warming
One of the commonly used pieces of evidence that humans are causing global warming is that there is a strong correlation between the increase in global carbon dioxide levels caused by human activities and the increase in global temperatures over the same timescale. Compare the following graph to the one above.
What is carbon footpring
The carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.
The carbon footprint can be reduced by reducing emissions of carbon dioxide and methane.
Ways to reduce carbon footprint
Why these actions may be limited
TRY TO MINIMISE:
use electricity at home, probably generated from fossil fuels, for lighting their room and using electronic devices
use a gas-powered boiler at home (which produces carbon dioxide) for heating and hot water
travel to school by bus or car (which probably runs on petrol or diesel)eat beef or rice which have been farmed using methods that release methane
travel abroad once per year on an aeroplane (which produces carbon dioxide)
It can sometimes be difficult for individuals to make all the changes that they would like to do to reduce their carbon footprint. For example, it might be too expensive to fit photovoltaic cells on the roof of your house, and you might work too far from your house to be able to cycle.
What is a major source of atmospheric pollutants and how
The combustion of fuels is a major source of atmospheric pollutants.
Most fuels, including coal, contain carbon and/or hydrogen and may also contain some sulfur.
The gases released into the atmosphere when a fuel is burned may include carbon dioxide, water vapour, carbon monoxide, sulfur dioxide and oxides of nitrogen. Solid particles and unburned hydrocarbons may also be released that form particulates in the atmosphere.
Complete vs incomplete combustion
Complete combustion of a hydrocarbon fuel occurs when there is a good supply of oxygen. It releases the maximum amount of energy and produces carbon dioxide and water.
Incomplete combustion of a hydrocarbon fuel occurs when there is a poor supply of oxygen. Less energy is released.
How is carbon monoxide and soot produced
VIA INCOMPLETE COMBUSTION
Water is still produced from the hydrogen atoms. Instead of carbon dioxide, you might get carbon monoxide or particulate carbon, known commonly as soot, or a mixture of both.
Soot is The fine black particles, chiefly composed of carbon, produced by incomplete combustion of coal, oil, wood, or other fuels.
Why is carbon monoxide so dangerous
Carbon monoxide is a toxic gas, but is also colourless and odourless, so we don’t know that we are being poisoned by carbon monoxide until it is often too late.]
Effects of carbon monoxide:
Toxic gas/poisnousgas because it is colourless and odourless
Soot is formed in incomplete combustion
Your red blood cells pick up this gas and carry it around your body instead of oxygen
How sulfur dioxide is produced when burning fuels
what is produces
Combustion of a fossil fuel which contains sulfur impurities
Sulfur dioxide is then further oxidised in the atmosphere to sulfur trioxide, SO3. This gas dissolves in rainwater to make
acid rain, which is a dilute solution of sulfuric acid, H2SO4.
Nitrogen oxides produced
what it produces
Oxidation of atmospheric nitrogen inside the engine of a car, lorry, etc
NOx gases can cause acid rain, and they also react in the atmosphere with other pollutants to make photochemical smog. Smog can have major health effects, causing asthma attacks and even death.
Properties and effects of atmospheric pollutants.
Carbon monoxide is a toxic gas. It is colourless and odourless and so is not easily detected.
Sulfur dioxide and oxides of nitrogen cause respiratory problems in humans and cause acid rain.
Particulates cause global dimming and health problems for humans.
Alternative methods of metal extraction
The Earth’s resources of metal ores are limited.
Copper ores are becoming scarce and new ways of extracting
copper from low-grade ores include phytomining, and bioleaching.
These methods avoid traditional mining methods of digging, moving
and disposing of large amounts of rock.
Phytomining uses plants to absorb metal compounds. The plants
are harvested and then burned to produce ash that contains metal
compounds.
Bioleaching uses bacteria to produce leachate solutions that
contain metal compounds.
The metal compounds can be processed to obtain the metal. For
example, copper can be obtained from solutions of copper
compounds by displacement using scrap iron or by electrolysis.
