Topic 9 - Chemistry of the Atmosphere Flashcards
Has the proportion of gases in the air changed much in 200 million years?
No
What is the composition of the atmosphere today? (3)
- 21% oxygen
- 78% nitrogen
- 1% other => 0.9% argon, 0.04% carbon dioxide, water vapour and trace quantities of the noble gases
Why is it difficult to gather evidence about the early atmosphere?
because it happened 4.6 billion years ago
How were volcanoes formed? (3)
- The surface of the early Earth was molten for millions of years with no atmosphere.
- As cooling slowly occurred, the molten surface began to slowly solidify into land masses.
- Volcanoes formed on the land masses.
What is one theory of how the early atmosphere formed? (2)
- One theory of how the early atmosphere formed suggests that the volcanoes released gases from the Earth’s interior through violent eruptions.
- These eruptions released large amounts of carbon dioxide and water vapour, as well as nitrogen, hydrogen, and other gases which may have included small proportions of ammonia and methane.
How were oceans formed from volcanoes? (2)
- While the surface of the Earth was still very hot the large quantities of water vapour (from volcanic eruptions) remained in the gaseous state.
- When conditions cooled sufficiently, the water vapour later condensed and fell to the surface of the Earth, forming the oceans.
How was the amount of carbon dioxide in the atmosphere reduced? (4)
- Carbon dioxide is a water soluble gas and dissolves readily.
- When the water vapour (from volcanic eruptions) condensed, large amounts of CO2 dissolved in the oceans.
- Carbonate substances were precipitated (deposited in solid from from a solution) during this process which later formed sediments.
- These processes reduced the amount of carbon dioxide in the atmosphere.
Why did oxygen levels increase? (3)
- Primitive plants and algae began photosynthesising which used up carbon dioxide from the atmosphere and released oxygen.
- Over billions of years, photosynthesis caused the amount of oxygen in the atmosphere to increase and the amount of carbon dioxide to decrease.
- This trend continued until around 200 million years ago when the composition of the atmosphere reached similar characteristics as today.
What did the increase in oxygen levels allow for?
allowed for more complex life forms to evolve
When did algae first evolve? What then happened?
Algae first evolved around 2.7 billion years ago and soon after this oxygen appeared in the atmosphere. Over the next billion years or so small green plants began to appear.
What were there high concentrations of in the early atmosphere?
Carbon dioxide
Why have the levels of carbon dioxide decreased? (5) - blurting / whiteboard
- When the water vapour in Earth’s early atmosphere condensed, large amounts of CO2 dissolved in the oceans.
- Carbonates were precipitated during this process which later formed sediments on the seabed.
- Green plants and algae began to evolve and absorbed considerable amounts of carbon dioxide during photosynthesis.
- Animals fed on the plants which transferred carbon to their tissues including bones and shells and when these organisms died, their remains formed sedimentary rocks.
- Dead organisms turn into fossil fuels, such as crude oil, natural gas and coal which ‘locked up’ the carbon.
What is the greenhouse effect - definition?
Greenhouse gases maintain the temperatures on Earth high enough to support life. This is known as the greenhouse effect.
What are three greenhouse gases?
- carbon dioxide
- methane
- water vapour
What is the greenhouse effect - process? (4) - blurting / whiteboard
- Short wavelength radiation (ultraviolet radiation) is emitted from the sun.
- When it strikes the earth’s surface, some of it is absorbed and some is re-emitted from the surface of the Earth as long wavelength radiation (infrared radiation).
- Much of the radiation is trapped inside the Earth’s atmosphere by greenhouse gases which can absorb and store the energy.
- Increasing levels of carbon dioxide and methane, although present in only small amounts, are causing significant upset to the Earth’s natural conditions by trapping extra heat energy.
Why are methane levels increasing? (2)
- More waste being sent to landfill sites due to an increasing human population.
- Increased levels of farming.
Why are carbon dioxide levels increasing? (2)
- The increased demand for energy resulting in more fossil fuels being burned.
- Deforestation- fewer trees means less carbon dioxide is removed from the atmosphere by photosynthesis.
What do many scientists believe about climate change, based on peer reviewed evidence?
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 are opinions on climate change varied generally?
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.
Why is there uncertainty surrounding historical data of climate change?
Historical data is much less accurate due to the lack of accurate instrumentation and methods. Fewer locations would also have been measured due to the lack of satellites and transport.
What have academic surveys shown most climate scientists believe? How many?
Academic surveys have shown that about 97% of climate scientists do believe human activity is causing climate change.
What is climate change?
Climate change is when there is a long term shift in worldwide weather patterns and conditions.
How are greenhouse gases causing climate change?
The vast majority of climate scientists agree that increasing levels of greenhouse gases are causing the average temperature of the Earth to increase. Temperature increases are leading to climate change.
What are 4 effects of climate change?
- Rising sea levels
- Frequent and intense droughts
- Storms
- Extreme heat waves and rainfall
How is climate change causing rising sea levels?
The melting of the polar ice caps and glaciers is leading to rising sea levels.
What are the impacts of rising sea levels? (3)
- Rising sea levels result in destructive erosion to coastal regions, flooding of wetlands and habitat destruction for birds, fish and plants.
- Low lying cities are likely to see increased flooding and permanent loss of usable land without expensive barrier systems.
- Increased soil salinity is also a consequence of rising sea levels.
How is frequent and intense droughts an impact of climate change? What are the impacts of these droughts? (2)
- Some regions are seeing devastating droughts leading to crop failure and collapse of agricultural production.
- Food production is greatly compromised leading to hardship and starvation.
How is climate change impacting storms? (2)
- The intensity of storms is increasing.
- Warmer ocean surfaces mean more moisture is entering the atmosphere so storms and hurricanes are more energetic and destructive.
What are the impacts of extreme heat waves and rainfall? (3)
- Extreme weather events are becoming more frequent resulting in great loss of life and destruction of infrastructure and ecosystems.
- Changing rainfall patterns are leading to uneven distribution of freshwater supplies.
- Lack of reliable freshwater supplies results in economic and political instability as neighbouring countries compete for dwindling resources.
What does carbon footprint mean?
Carbon footprint refers to the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.
What is one way of measuring carbon footprint?
A Life Cycle Assessment
What is a life cycle assessment?
A life cycle assessment technique is used to assess the environmental impact associated with all the stages in the life cycle of a product, a service or an event.
What is the general way to reduce carbon footprint?
The carbon footprint can be reduced by reducing emissions of carbon dioxide and methane.
How can renewable energy be used to reduce carbon emissions?
CO2 emissions can be reduced by using renewable energy supplies such as solar or wind energy instead of burning fossil fuels.
How are governments and global organisations reducing carbon footprints?
Governments and global organisations are slowly switching to greener and sustainable sources of energy and often offer financial incentives to companies in an effort to convince them to “go green”.
What are some ways to reduce carbon footprint other than using renewable energy? (7)
- Cutting out unnecessary journeys
- Using public transport rather than private cars
- Reducing consumption of meat
- Buying locally sourced foods to reduce food miles
- Carbon off-setting
- Switching to electric vehicles
- Recycling and re-using materials to prevent them being sent to landfill
What is carbon off-setting?
Paying for reforestation projects to compensate for carbon emissions from flying for example.
How can governments reduce carbon footprint on an industrial scale?
by investing in carbon capture schemes
How do carbon capture schemes work? (3)
- Carbon capture refers to a range of technologies used to trap atmospheric carbon dioxide from power generation and other industries.
- The carbon dioxide is stored deep underground in porous rocks from which oil and gas have been extracted.
- The logic here is to restore the balance in the carbon cycle, by locking up carbon in the Earth’s crust where it was previously stored as fossil fuels.
What difficulties have to be overcome in order to reduce carbon and greenhouse gas emissions? (4)
- Alternative technologies are still in their infancy
- Governments tend to be slow to act on these issues as they fear a negative impact on their economies
- On an individual level, there is also resistance as it is difficult to convince people to change their ways
- There is a lack of investment schemes for companies to help them to modernise their facilities
Why should climate mitigation strategies be adopted?
Ultimately, many people believe that reducing the global carbon footprint will be too expensive and not enough to tackle climate change, so climate mitigation strategies should be adopted hand in hand with carbon footprint reduction.
What are some climate mitigation strategies? (5)
- Changing the type of crops grown in different regions
- Investing in flood defence systems or building houses on stilts
- Changing building infrastructure to make it more resistant to extreme weather
- Repurposing land vulnerable to flooding
- Using heat sinks to make buildings more efficient
What is the major source of atmospheric pollution?
The combustion of fossil fuels is the major source of atmospheric pollution.
What are some fossil fuels?
coal, oil, natural gas, oil shales and tar sands
What does the combustion of fossil fuels release? (2 bullet points)
- The burning of fossil fuels releases the gases carbon dioxide, water vapour, carbon monoxide, oxides of nitrogen and oxides of sulfur.
- In addition, incomplete combustion of the fuels gives rise to unburnt hydrocarbons and carbon particulates.
What is a fuel?
A fuel is a substance which releases energy in an exothermic reaction.
Where does incomplete combustion sometimes occur?
It occurs in some appliances such as boilers and stoves as well as in internal combustion engines.
What may be produced in incomplete combustion?
In addition to water, carbon particles (soot) and carbon monoxide may be produced during incomplete combustion.
How are oxides of nitrogen produced in a car engine? (3)
- Although nitrogen is not present in fossil fuels, nitrogen oxides are a product of the combustion of fuels in car engines.
- The oxides are mostly a mixture of nitrogen monoxide and nitrogen dioxide.
- Nitrogen is normally an unreactive gas, but high temperatures inside combustion engines can make nitrogen in the air react with oxygen to produce oxides of nitrogen.
How is sulfur dioxide produced in a car engine? (3)
- Fossil fuels are often contaminated with small amounts of sulfur impurities.
- When these contaminated fossil fuels are combusted, the sulfur in the fuels get oxidised to sulfur dioxide.
- Sulfur dioxide is a major atmospheric pollutant.
Why is carbon monoxide poisoning so severe? (3)
- Carbon monoxide is an extremely poisonous gas as it combines with haemoglobin in blood and prevents it from carrying oxygen.
- It is particularly dangerous as it is colourless and odourless, making it difficult to detect.
- A lack of oxygen supply to the brain can lead to fainting, a coma or death.
How is soot formed?
Solid carbon particles (or particulates) released from incomplete combustion clump together to form soot which gradually falls back to the ground.
Why is releasing particulates a problem? (3)
- If they are inhaled they can damage the lungs and cause respiratory problems.
- They can cover buildings and statues, making them look unclean and accelerating corrosion.
- They can reflect sunlight back into space reducing the amount of light reaching the earth, this is called global dimming.
What is sulfur dioxide?
Sulfur dioxide is a colourless, pungent smelling gas that is a major air pollutant responsible for acid rain.
How is acid rain formed?
- When sulfur dioxide is released, it mixes with clouds and readily dissolves in rainwater.
- SO(2) is a non-metal oxide so it forms an acidic solution in water, hence forming acid rain, H(2)SO(4).
Why is acid rain dangerous? (4)
- Acid rain causes corrosion to metal structures, buildings and statues made of carbonate rocks.
- It causes damage to aquatic organisms.
- It pollutes crops and water supplies.
- It irritates lungs, throats and eyes.
What else contributes to acid rain other than sulfur dioxide?
oxides of nitrogen
What are the dangers of oxides of nitrogen other than acid rain?
Aside from acid rain, oxides of nitrogen produce photochemical smog and breathing difficulties, in particular for people suffering from asthma.
Are greenhouse gases and atmospheric pullutants the same thing? Why? (2)
- Greenhouse gases and atmospheric pollutants are not the same thing.
- A greenhouse gas causes global warming whereas a pollutant is something which is not found in clean air and which causes problems close to the ground such as smog and breathing difficulties.
