Combined Chemistry - C9 Chemistry of the atmosphere

Question 1

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

Answer 1

200 million years

Question 2

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

Answer 2

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

Question 3

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

Answer 3

• Water vapour
• Noble gases
• Carbon dioxide

Question 4

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

Answer 4

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

Question 5

One theory suggest that the Earth’s early atmosphere was shaped by intense volcanic activity.

a) Name the planets that have similar atmospheric conditions to those described by this theory.
b) What was the main gas present in the atmosphere at this time?

Answer 5

a) Mars and Venus
b) Carbon dioxide

Question 6

How do most scientists believe the oceans were formed?

Answer 6

Water vapour in the early atmosphere condensed to form the oceans

Question 7

Describe the composition of gases in the early atmosphere.

Answer 7

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

Question 8

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

Answer 8

• 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 9

Write a word and balanced symbol equation for photosynthesis.

Answer 9

carbon dioxide + water → glucose + oxygen

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Question 10

Describe how the oxygen levels in the early atmosphere increased?

Answer 10

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

Question 11

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

Answer 11

Reduced carbon dioxide in the atmosphere (by photosynthesising)

Question 12

Describe how limestone is formed

Answer 12

• 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 13

Describe how coal is formed.

Answer 13

• 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 14

Describe how crude oil is formed.

Answer 14

• 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 15

Describe how natural gas is formed.

Answer 15

• 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 16

Name the three main greenhouse gases.

Answer 16

• Water vapour
• Carbon dioxide
• Methane

Question 17

Explain what is meant by the ‘Greenhouse Effect’.

Answer 17

• 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 18

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

Answer 18

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 19

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

Answer 19

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 20

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

Answer 20

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

Question 21

List three consequences of climate change.

Answer 21

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 22

What is meant by ‘carbon footprint’?

Answer 22

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

Question 23

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

Answer 23

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 24

What is the cause of global dimming?

Answer 24

Solid particulates released from burning fuels

Question 25

Name the two gases that cause acid rain

Answer 25

• Sulfur dioxide
• Oxides of Nitrogen

Question 26

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

Answer 26

• Sulfur dioxide
• Oxides of Nitrogen

Question 27

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

Answer 27

Carbon monoxide

Question 28

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

Answer 28

Incomplete combustion

Question 29

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

Answer 29

Sulfur dioxide