C9- Chemistry of the Atmosphere

Question 1

What percentage of the current atmosphere is made up of nitrogen?

Answer 1

78%

Question 2

What percentage of the current atmosphere is made up of oxygen?

Answer 2

21%

Question 3

What percentage of the current atmosphere is made up of carbon dioxide?

Answer 3

0.05%

Question 4

What other gases are found in the current atmosphere?

Answer 4

Water vapour
Noble gases such as argon

Question 5

How long have the proportions of gases been the same as the current atmosphere?

Answer 5

200 million years

Question 6

How old is the earth?

Answer 6

Around 4.6 billion years old

Question 7

Why is evidence of the early atmosphere limited?

Answer 7

The timescale of 4.6 billion years

Question 8

In the first billion years of the earth’s existence, what was there that released gases to form the early atmosphere?

Answer 8

Intense volcanic activity

Question 9

How were oceans formed?

Answer 9

Water vapour released by volcanic eruptions condensed to form the oceans

Question 10

What did the early atmosphere many consist of?
Why?

Answer 10

It mainly consisted of carbon dioxide because when volcanos erupted they released a lot of carbon dioxide

Question 11

What was the earth’s early atmosphere similar to?
Why?

Answer 11

Mars and venus because it was made up of mainly carbon dioxide with very little oxygen

Question 12

What other gases (other than carbon dioxide and water vapour) did volcanos release?

Answer 12

Nitrogen and small proportions of ammonia and methane

Question 13

What do all fossil fuels contain?
Where did it come from?

Answer 13

They all contain trapped carbon which was part of the carbon dioxide taken in for photosynthesis

Question 14

Name 3 main differences between the earth’s current atmosphere and its early atmosphere

Answer 14

There is now more nitrogen
Less carbon dioxide
Amounts of oxygen have increased

Question 15

What happened when carbon dioxide dissolved in the oceans?

Answer 15

It formed a weak acid which reacted with minerals in the sea to form precipitates. Over time, this formed sediments of carbonate rock on the sea bed.

Some of the carbon dioxide waw used to make coral and shells of some organisms (e.g. mussels). When they died it formed the sedimentary rock limestone.

Question 16

How did oxygen in the atmosphere increase?

Answer 16

Around 2.7 billion years ago photosynthetic algae evolved in the oceans and they produced oxygen from photosynthesis. Over the following billion years, plants evolved releasing more oxygen into the atmosphere.

Question 17

How did levels of carbon dioxide fall in the atmosphere?

Answer 17

Organisms take in carbon dioxide for photosynthesis. This carbon can then be trapped in fossil fuels

Question 18

How was coal formed?

Answer 18

Coal is formed from the remains of ferns and trees which died in marshy wetlands and therefore could not decompose. Over time the remains are covered with sediment and compressed. High temperature and pressure forms coal.

Question 19

How is crude oil formed?

Answer 19

Oil is formed from plankton which have died and settled in mud on the sea bed. If oxygen isn’t present they cannot decompose and over time they are compressed by sediment. The heat and pressure forms crude oil.

Question 20

What is natural gas mainly made up of?

Answer 20

The hydrocarbon methane

Question 21

Where is natural gas usually found?

What fossil fuel is it formed similarly to?

Answer 21

Near oil reserves

Oil

Question 22

What are the three main greenhouse gases in the atmosphere?

Answer 22

Carbon dioxide
Water vapour
Methane

Question 23

Why do we need greenhouse gases?

Answer 23

To keep temperatures on earth at a suitable level to support life

Question 24

What is the greenhouse effect?

Answer 24

Energy from the sun travels to the Earth as short wavelength radiation (e.g. ultraviolet and visible light)

Some of the short wavelength radiation reflects off of the atmosphere and back into space but most of it passes straight through the atmosphere as short wavelength radiation does not interact strongly with the gas molecules in the atmosphere.

The energy of the radiation is absorbed when it teaches the surface of the earth. The surface of the earth then radiates the energy as long wavelength radiation (e.g. infra-red).

Some of the long wavelength radiation reacts with greenhouse gas molecules in the atmosphere so the long length radiation is absorbed. Because the energy is trapped in the atmosphere it causes the temperature of the atmosphere to increase.

Question 25

Name four causes of climate change

Answer 25

Deforestation which releases carbon dioxide
Burning fossil fuels for electricity, petrol, heating homes etc.
Agriculture such as cattle farming and growing rice in flooded paddy fields releases methane

Question 26

Name three effects of climate change

Answer 26

Increased temperatures will melt ice caps, causing sea levels to rise. This will cause increased flooding in low lying areas and therefore habitat loss.

More severe weather, such as increased storms and more frequent droughts

Change in the distribution of animals and the distribution of insect borne diseases such as malaria

Question 27

What is complete combustion?

What is the equation?

Answer 27

When a fuel is burnt with plenty of oxygen so the hydrocarbon can be fully oxidised

Hydrocarbon + Oxygen –> Carbon Dioxide + Water Vapour

Question 28

How do you get sulfur dioxide from burning fuels?

Answer 28

Some fuels such as coal contain sulfur. When the coal is burnt the sulfur atoms are oxidised which produced sulfur dioxide