Chemistry of the Atmosphere - C9

Question 1

How long has the proportions of different gases in the
atmosphere been the same as they are today?

Answer 1

• about four-fifths (approximately 80%) nitrogen
• about one-fifth (approximately 20%) oxygen
• small proportions of various other gases, including carbon
  dioxide, water vapour and noble gases.

Question 2

Why is evidence for the Earth’s early atmosphere limited?

Answer 2

The time scale of 4.6 billion years.

Question 3

1) Volcanic activity

Answer 3

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. 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.

Question 4

2) Oceans

Answer 4

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.

Question 5

3) Oxygen

Answer 5

Algae and plants produced the oxygen that is now in the
atmosphere by photosynthesis. 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.

Question 6

4) Carbon dioxide

Answer 6

Carbon dioxide dissolved into the oceans. It then went through a series of reactions to form carbonate precipitates that formed sediments on the seabed. Algae and plants decreased the percentage of carbon dioxide in the atmosphere by photosynthesis. Later, marine animals evolved. Their shells and skeletons contained carbonates from the oceans. Carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon.

Question 7

Formation of crude oil, coal, limestone and sedimentary rock.

Answer 7

When plants, planktons and marine animals die, they fall to the seabed and get buried by layers of sediment. Over millions of years, they become compressed and form sedimentary rocks, oil and gas - trapping the carbon within them.

Crude oil are formed from deposits of plankton . These fossil fuels form reservoirs under the seabed when they get trapped in rocks.

Coal is a sedimentary rock made from thick plant deposits.

Limestone is a sedimentary rock. It’s made of calcium carbonate deposits from the shells and skeletons of marine organisms.

Question 8

What do greenhouse gases do?

Answer 8

Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life.

Question 9

What are greenhouse gases?

Answer 9

Water vapour, carbon dioxide and methane.

Question 10

Describe the greenhouse effect in terms of the interaction of short and long wavelength radiation with matter.

Answer 10

Greenhouse gases do not absorb the short wavelength radiation from the sun- but they do absorb the long wavelength radiation that gets reflected back off the Earth They then re-radiate it in all directions including back towards the Earth. The longwave radiation is thermal radiation so it results in warming of the surface of the Earth.

Question 11

What are some human activities that affect the amount of greenhouse gases in the atmosphere?

Answer 11

Deforestation: fewer trees means less CO2 is removed from the atmosphere via photosynthesis.

Burning fossil fuels: carbon that was “locked up” in these fuels is released as carbon dioxide.

Agriculture: More farm animals produce more methane through their digestive processes.

Creating waste: More landfill sites and more waste from agriculture means more CO2 and methane released by decomposition of waste.

Question 12

Based on peer-reviewed evidence, what do many scientists believe?

Answer 12

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.

Question 13

What is the problem with trying to model complex systems such as global climate change?

Answer 13

It 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.

Question 14

What is a major cause of climate change?

Answer 14

An increase in average global temperature.

Question 15

What are four potential effects of climate change?

Answer 15

1) Melting polar ice caps - causing a rise in sea levels, increased flooding in coastal areas and coastal erosion.

2) Changes in rainfall patterns - some regions get too much or too little water. This along with temperature may affect the ability of certain regions to produce food.

3) The frequency and severity of storms may increase.

4) Changes in temperature and the amount of water available in a habitat may affect wild species leading to their differences in distribution.

Question 16

What is the carbon footprint?

Answer 16

The total amount of carbon dioxide and other
greenhouse gases emitted over the full life cycle of a product,
service or event.

Question 17

How do you reduce your carbon footprint?

Answer 17

By reducing emissions of
carbon dioxide and methane.

Question 18

Ways to reduce your carbon footprint?

Answer 18

Renewable energy sources or nuclear energy could be used instead of fossil fuels.

Using more efficient processes could conserve energy and cut waste. Lots of waste decomposes to release methane.

Governments could tax companies or individuals based on the amount of greenhouse gases they emit.

Governments could put a cap on emissions of all greenhouse gases that companies make - then sell licences for emissions up to that cap.

There’s also technology that captures the CO2 produced by burning fossil fuels before it’s released into the atmosphere - it’s then stored deep underground in cracks in the rock.

Question 19

Why actions to reduce emissions of carbon dioxide and methane may be limited?

Answer 19

There is a lot of work to be done on alternative technologies that result in lower Co2 emissions.

Many governments are worried that making these changes will impact on the economic growth of communities - which could be bad for people’s well-being.

It’s hard to make international agreements to reduce emissions. Most countries don’t want to sacrifice their economic development if they think others won’t do the same.

Individuals may not want to change and there is not enough education provided about why the changes are necessary and how to make them.

Question 20

What is a major source of atmospheric pollutants?

Answer 20

The combustion of fuels.

Question 21

What do most fuels, including coal, contain?

Answer 21

Carbon and/or hydrogen and may also contain some sulfur.

Question 22

When a fuel is burned, what gases may be released into the atmosphere?

Answer 22

Carbon dioxide, water vapour, carbon monoxide, sulfur dioxide and oxides of nitrogen.

Question 23

How are particulates formed?

Answer 23

Solid particles and unburned
hydrocarbons released into the air.

Question 24

How is carbon monoxide produced?

Answer 24

Incomplete combustion.

Question 25

Why is carbon monoxide dangerous?

Answer 25

It’s a toxic gas. It’s colourless and odourless so hard to detect. It binds to your haemoglobin in your blood so less oxygen is carried and transported around your body. A lack of oxygen in the blood can lead to fainting, a coma or even death.

Question 26

How is sulfur dioxide produced?

Answer 26

It’s released during the combustion of fossil fuels, such as coal, that contain sulfur impurities - the sulfur in the fuel becomes oxidised.

Question 27

How are oxides of nitrogen produced?

Answer 27

From a reaction between nitrogen and oxygen in the air, caused by the heat of the burning. This can happen in the internal combustion engines of cars.

Question 28

Why is sulfur dioxide and oxides of nitrogen dangerous?

Answer 28

When these gases mix with clouds they form dilute nitric acid or dilute sulfuric acid. This falls as acid rain. Acid rain kills plants, damages buildings and statues and also makes metal corrode.

They cause respiratory problems if they’re breathed in.