C13 - The Earth's Atmosphere

Question 1

What are the proportions of gases in the atmosphere today?

Answer 1

80% Nitrogen
20% Oxygen

Small proportions of other gases:

• Carbon Dioxide
• Water Vapour

Question 2

Why are scientists not certain of what the Earth’s early atmosphere was like?

Answer 2

The Earth is 4.6 billion years old - there is a lack of evidence.

Question 3

What is the name of the theory behind the origin of the Earth’s early atmosphere?

Answer 3

The Volcanic Activity Theory for the Origin of the Atmosphere

Question 4

What gases were released during the first billion years of the Earth’s existence?

Answer 4

Due to the intense volcanic activity, CO2 and H2O were the main gases released.

Question 5

How did the oceans form?

Answer 5

Volcanoes released water vapour that condensed to form the oceans.

Question 6

What 2 planets was the Earth’s early atmosphere most like?

Answer 6

Mars and Venus - mainly CO2 and little to no Oxygen.

Question 7

What other gases made up the early atmosphere in smaller proportions?

Answer 7

Nitrogen, Methane and Ammonia

Question 8

How did the levels of CO2 in the atmosphere begin to decrease?

Answer 8

• CO2 dissolved into the newly formed oceans.
• CO2 used up in plant and algae photosynthesis.
• CO2 also used in producing sedimentary rocks (limestone - CaCO3)

Question 9

Why did the Oxygen levels begin to increase?

Answer 9

Plants and algae began to photosynthesise, which produced and increased the demand for Oxygen.

Question 10

Why did Methane and Ammonia levels decrease?

Answer 10

They got used up as they reacted with the oxygen produced by photosynthesis.

Question 11

Why did Nitrogen levels increase?

Answer 11

Nitrogen is unreactive so was able to accumulate in the atmosphere.

Question 12

What 2 sedimentary rocks were formed as the atmosphere evolved?

Answer 12

1) Limestone - CaCO3

2) Coal

Question 13

How did Limestone form?

Answer 13

• CO2 dissolved in oceans to form Carbonate ions.
• Carbonate ions used by marine organisms to build shells/skeletons out of calcium carbonate.
• Upon death, the shells/skeletons sunk.
• Shells/skeletons buried and compressed over millions of years to form limestone.

Question 14

How did Coal form?

Answer 14

• Plants and trees died in swamps and decayed in the absence of oxygen.
• Compressed over millions of years to form Coal.

Question 15

How did Crude Oil and Natural gas form?

Answer 15

• Formed from the ancient biomass of plankton buried in mud.
• Remains of plankton covered by more sediment.
• Compressed over millions of years to from Crude Oil and Natural Gas

Temperature during burial/compression determines whether oil/gas produced.

Question 16

Why has the amount of CO2 in the atmosphere remained fairly constant in the last 200 million years?

Answer 16

The Carbon Cycle

Question 17

What is the major source of atmospheric pollutants?

Answer 17

Combustion of fuels (mostly hydrocarbons).

Question 18

What do most fuels contain?

Answer 18

Carbon, Hydrogen and some traces of Sulfur.

Question 19

What are the 6 major atmospheric pollutants?

Answer 19

1) Carbon Dioxide, CO2
2) Water Vapour, H2O
3) Carbon Monoxide, CO
4) Sulfur Dioxide, SO2
5) Nitrogen Oxides, NOx
6) Solid Particulates / Unburned Fuel

Question 20

How are Carbon Dioxide and Water Vapour produced industrially?

Answer 20

They are produced by the complete combustion of hydrocarbon fuels.

E.g Methane: CH4 + O2 —> CO2 + H2O

Question 21

What are the effects of Carbon Dioxide in the atmosphere?

Answer 21

• Main greenhouse gas.

- Enhances greenhouse effect and causes global warming/climate change.

Question 22

What are the effects of water vapour in the atmosphere?

Answer 22

None.

Question 23

How can CO2 in the atmosphere be reduced?

Answer 23

Burning less fossil fuels/hydrocarbon fuels.

Question 24

How is Carbon Monoxide produced?

Answer 24

Produced by the incomplete combustion of hydrocarbon fuels (insufficient oxygen).

Question 25

What are the effects of Carbon Monoxide in the atmosphere?

Answer 25

• Toxic, colourless and odourless gas.
• Binds well to heamoglobin.
• Can cause respiratory problems and even death.

Question 26

How can Carbon Monoxide in the atmosphere be reduced?

Answer 26

Ensure that there is a good oxygen supply for combustion.

Question 27

How is Sulfur Dioxide produced?

Answer 27

Sulfur reacts with oxygen during combustion.

Question 28

What are the effects of Sulfur Dioxide in the atmosphere?

Answer 28

• Causes acid rain.

- Causes respiratory problems.

Question 29

How can Sulfur Dioxide in the atmosphere be reduced?

Answer 29

• Remove sulfur from the fuel before burning.

- Reduce the burning of fossil fuels.

Question 30

How are Nitrogen Oxides produced?

Answer 30

Nitrogen reacts with oxygen at high temperatures in engines.

Question 31

What are the effects of Nitrogen Oxides?

Answer 31

• Causes Acid rain.

- Causes respiratory problems.

Question 32

How can Nitrogen Oxides in the atmosphere be reduced?

Answer 32

-Use catalytic converters in cars - converts harmful gases into less harmful gases.

E.g:

• Carbon Monoxide into Carbon Dioxide.
• Nitrogen Oxide into Nitrogen and Water.

Question 33

How are solid particulates / unburned fuels produced?

Answer 33

When fuels (e.g Diesel) don’t burn completely, tiny particles of carbon (soot) and unburned fuel are produced.

Together these are called particulates.

Question 34

What are the effects of solid particulates in the atmosphere?

Answer 34

• Lung Damage

- Global Dimming - particulates in the upper atmosphere reflect sunlight back into space, away from the earth.

Question 35

How can solid particulates in the atmosphere be reduced?

Answer 35

Ensure that there is always a good oxygen supply for combustion.