Chemistry of the atmosphere

Question 1

Describe how the oxygen levels in the early atmosphere increased?

Answer 1

• Algae produced oxygen by photosynthesis 2.7 billion years ago.
• Over the next billion years, plants evolved and produced oxygen by photosynthesis.

Question 2

Write a word and balanced symbol equation for photosynthesis.

Answer 2

Question 3

As well as increasing oxygen levels, what other effect did algae and plants have on the atmosphere?

Answer 3

Reduced carbon dioxide in the atmosphere (by photosynthesising)

Question 4

One theory suggests that the Earth’s early atmosphere was shaped by intense volcanic activity. What was the main gas present in the atmosphere at this time?

Answer 4

Carbon dioxide

Question 5

What are the issues with the way in which the media portrays global climate change?

Answer 5

The media portrays simplified models, speculation and opinions which may lead to bias.

Question 6

How did the amount of carbon dioxide in the early atmosphere reduce?

Answer 6

• Dissolved in the oceans
• Locked up in sedimentary rocks (carbonate precipitate forming sediment)
• Locked up in fossil fuels (calcium carbonate shells of marine organisms)

Question 7

What are the approximate proportions of nitrogen and oxygen in our atmosphere (as a fraction and percentage)?

Answer 7

• Nitrogen (4/5 or 80%)
• Oxygen (1/5 or 20%)

Question 8

What type of combustion often results in carbon monoxide and soot (carbon particles) being released?

Answer 8

Incomplete combustion

Question 9

Explain what is meant by the ‘Greenhouse Effect’.

Answer 9

• The Greenhouse Effect is the warming of the Earth’s surface due to greenhouse gases.
• The greenhouse gases don’t absorb the short wave radiation from the sun
• However, they do absorb the long wavelength radiation that is reflected off the Earth’s surface.
• They then re-radiate this long-wavelength radiation, some of which travels back towards Earth - giving a warming effect.

Question 10

Why is there only limited evidence of what the early atmosphere was like and how it evolved?

Answer 10

Because there is such a large timescale (4.6 billion years).

Question 11

Do most scientists agree that human activities are causing global climate change?

Answer 11

Yes, evidence for climate change has been peer- reviewed and most scientists believe human activities will cause the Earth’s temperature at the surface to rise.

Question 12

Describe how coal is formed.

Answer 12

• Plant deposits fall to the bottom of the sea.
• The plant deposits are covered by layers of sediment.
• Over millions of years, the plant deposits are compressed and coal is formed.

Question 13

Describe how crude oil is formed.

Answer 13

• Deposits of dead plankton collect at the bottom of the sea.
• They become buried by layers of sediment and are compressed over millions of years.
• Crude oil and natural gas are then formed and are found as resevoirs deep underground.

Question 14

Name the two gases that cause acid rain.

Answer 14

• Sulfur dioxide
• Oxides of Nitrogen

Question 15

For approximately how many years have the proportion of gases in the atmosphere stayed the same?

Answer 15

200 million years

Question 16

What is the cause of global dimming?

Question 17

Name the toxic, colourless and odourless gas that can be released when burning fuels.

Answer 17

Carbon monoxide

Question 18

Name the two gases that can be released by burning fuels that cause respiratory problems in humans.

Answer 18

• Sulfur dioxide
• Oxides of Nitrogen

Question 19

If a fuel contains sulfur impurities, what gas will be released during combustion of the fuel?

Answer 19

Sulfur dioxide

Question 20

One theory suggests that the Earth’s early atmosphere was shaped by intense volcanic activity. Name the planets that have similar atmospheric conditions to those described by this theory.

Answer 20

Mars and Venus

Question 21

Suggest three ways to reduce your carbon footprint by reducing emissions of carbon dioxide and methane.

Answer 21

Suggestions include:

• Eating more locally sourced food
• Fewer car journeys (e.g. car pooling or
• walking/cycling instead)
• Using renewable energy to power your home
• Producing less waste (e.g. buying products with less packaging)
• Reusing or Recycling Products

Question 22

Describe how natural gas is formed.

Answer 22

• Deposits of dead plankton collect at the bottom of the sea.
• They become buried by layers of sediment and are compressed over millions of years.
• Crude oil and natural gas are then formed and are found as reservoirs deep underground.

Question 23

List three consequences of climate change.

Answer 23

• Any three from:
• Sea levels rising
• Increased flooding in coastal areas
• Increased frequency of droughts
• Changes in rainfall patterns
• Increase in frequency and severity of extreme weather events (e.g. storms)
• Changes in distribution of wild animals and plants

Question 24

Name the three main greenhouse gases.

Answer 24

• Water vapour
• Carbon dioxide
• Methane

Question 25

Describe how limestone is formed.

Answer 25

* Dead marine organisms fall to the bottom of the sea. * Their calcium carbonate shells and skeletons are compressed over millions of years. * Calcium carbonate rock (limestone) is formed. This is a sedimentary rock.

Question 26

What is meant by ‘carbon footprint’?

Answer 26

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

Question 27

Suggest two human activities that increase the amount of greenhouse gases (e.g. methane and carbon dioxide).

Answer 27

* Any two from: * Agriculture/Farming (farm animals produce large amounts of methane) * Creating waste (decomposition produces CO2) * Deforestation (fewer trees means less CO2 is * absorbed through photosynthesis) * Burning fossil fuels (’locked up’ carbon is released as CO2 is produced)

Question 28

Describe the composition of gases in the early atmosphere.

Answer 28

* Mainly carbon dioxide * With small amounts of methane and ammonia

Question 29

How do most scientists believe the oceans were formed?

Answer 29

* Water vapour in the early atmosphere * Condensed to form the oceans

Question 30

Other than Nitrogen and Oxygen, name some gases that are present in very small quantities in our atmosphere.

Answer 30

Water vapour, noble gases, carbon dioxide.