Earth and Atmosphere

Question 1

What percentage of the atmosphere today is made up of

nitrogen?

Answer 1

78%

Question 2

What percentage of the atmosphere today is made up of

oxygen?

Answer 2

21%

Question 3

What percentage of the atmosphere today is made up of

argon?

Answer 3

0.9%

Question 4

What percentage of the atmosphere today is made up of

carbon dioxide?

Answer 4

0.037%

Question 5

How long ago did cyanobacteria evolve?

Answer 5

2.7 billion years ago

Question 6

What was so special about

cyanobacteria?

Answer 6

they were the first creature to photosynthesise

Question 7

What is the equation for

photosynthesis?

Answer 7

carbon dioxide + water -> oxygen + glucose

6CO2 + 6H2O -> 6O2 + C6H12O6

Question 8

Where is most of the carbon from the original carbon dioxided now locked up in?

Answer 8

• coal
• natural gas
• sedimentary rock
• oil

Question 9

What are the causes of

carbon dioxide

as a pollutant in the air?

Answer 9

combustion
respiration

Question 10

What are the causes of

sulfur dioxide

as a pollutant in the air?

Answer 10

burning of coal

(burning the sulfur impurities)

Question 11

What are the causes of

carbon particulates (soot)

as a pollutant in the air?

Answer 11

burning wood and fossil fuels

Question 12

What are the causes of

carbon monoxide

as a pollutant in the air?

Answer 12

incomplete combustion

Question 13

What are the causes of

nitrogen dioxide

as a pollutant in the air?

Answer 13

internal high temperature combustion engines

(e.g. cars)

Question 14

What effects on the environment does the air pollutant carbon dioxide have?

Answer 14

it reflects radiation back into the earth’s atmosphere - contributing to global warming

(and the greenhouse effect)

Question 15

What effects on the environment does the air pollutant sulfur dioxide have?

Answer 15

It binds with water vapour in clouds to produce acid rain. This acid rain destroys forests, erodes limestone buildings and kills aquatic life.

Question 16

What effects on the environment does the air pollutant soot have?

Answer 16

it can cause lung damage and lung cancer

Question 17

What effects on the environment does the air pollutant carbon monoxide have?

Answer 17

it binds to haemoglobin in the blood and stops oxygen from getting to cells

Question 18

What effects on the environment does the air pollutant nitrogen dioxide have?

Answer 18

it forms photochemical smog

(and acid rain)

Question 19

How is acid rain formed?

Answer 19

1. Fuels contain sulfur compouds as impurities and when burnt will generate sulfur dioxide (SO2).
2. This sulfur dioxide then reacts with water to make ‘sulfurous acid’, H2SO3.
3. Sulfurous acid reacts with oxygen to form sulfuric acid, H2SO4.
4. A combination of acids fall as acid rain.

Question 20

What problems are caused by

acid rain?

Answer 20

• it destroys forests
• it erodes limestone buildings
• it kills aquatic life

Question 21

What are the benefits of burning hydrogen as an alternative?

Answer 21

• it is more efficient
• it is a renewable resource

Question 22

What is the difference between

green hydrogen and blue hydrogen?

Answer 22

Green Hydrogen:
- from electrolysing water using photovoltaic cells (from the sun)

Blue Hydrogen:
- from the reaction between methane (not renewable) and steam
- this uses non-renewable resources to create a greenhouse gas :[[[

Question 23

What are the positives of

hydrogen in cars?

Answer 23

• lower engine temperature
• no pollutants formed during driving

Question 24

What are the negatives of

hydrogen in cars?

Answer 24

• highly explosive
• not readily available
• difficult to store safely
• low density (low energy to volume ratio)

Question 25

# What makes water safe to drink?

Answer 25

- low salt concentration - free from pathogens - no large particles

Question 26

# What steps are necessary to obtain potable water?

Answer 26

- choose a source of water - filter to remove large objects - sterilise (kill microbes)

Question 27

How can desalination be carried out?

Answer 27

- distillation - reverse osmosis using membranes | this process requires a lot of energy

Question 28

What are the steps that are necessary to treat waste water?

Answer 28

1. Screening and grit removal 2. Sedimentation to produce sewage sludge and effluent 3. Anaerobic digestion of sewage sludge ○ Biogas produced ○ Remaining sludge can be used as fuel 4. Aerobic biological treatment of effluent ○ Effluent can now be discharged back into rivers

Question 29

What formed the Earth's early atmosphere?

Answer 29

gases produced by volcanic activity

Question 30

What was Earth's early atmosphere thought to contain?

Answer 30

- little or no oxygen - a large amount of carbon dioxide - water vapour - small amounts of other gases

Question 31

How did Earth's oceans form?

Answer 31

1. The earth has just formed and is a ball of molten rock. 2. Its atmosphere consists of hydrogen and helium. 2. As the ball cools, a crust forms 3. Volcanoes burst forth from the molten rock below. 4. These volcanoes erupt and gave out gases such as carbon dioxide, ammonia, methane and steam. 5. As the earth cools down even more, this steam condenses and falls as rain. 6. It fills up hollows in the Earth's crust and thus the oceans are formed.

Question 32

How did organisms start life on land?

Answer 32

1. At first, there is no ozone layer, so the UV light from the sun is too intense for anything to live on land. So the first living things appear in the oceans. 2. These organisms evolve into simple plants, like algae. 3. These organisms use up carbon dioxide in photosynthesis and make the first molecules of oxygen. 4. After some time, the oxygen starts to build up in the atmosphere. Some of this reacts to form the ozone layer, which shields the Earth from harmful UV light. 5. This allows organisms to leave the water and start to live on land.

Question 33

What is the chemical test for oxygen?

Answer 33

- collect the gas in a test tube - test with a glowing splint - oxygen will relight a glowing splint