C13 - The Earth's Atmosphere

Question 1

When was the Earth’s early atmosphere formed?

Answer 1

4.6 billion years ago

Question 2

How do we know what Earth’s early atmosphere was like?

Answer 2

gas bubbles trapped in ancient rocks and ice

Question 3

What are these compounds:
CO₂
H₂O
N₂
CH₄
NH₃

Answer 3

carbon dioxide
water
nitrogen
methane
ammonia

Question 4

How might the early atmosphere have formed?

Answer 4

Volcanoes releasesd CO_{2 (g)}, H₂O _(g), and N_{2 (g)}. The H₂O _(g) condensed as the Earth cooled down which formed precipitation. There were also trace amounts of CH_{4 (g)} and NH_{3 (g)} in the atmosphere. There was little to no oxygen.

Question 5

What was the percentage of gases in Earth’s early atmosphere?

Answer 5

95% carbon dioxide
3.1% nitrogen
1.2% argon
0.2% methane

Question 6

When do scientists think life began?

Answer 6

3.4 billion years ago

Question 7

When do scientists think algae evolved?

Answer 7

2.7 billion years ago

Question 8

How did oxygen levels increase in the evolving atmosphere?

Answer 8

Algae photosynthesized which produced oxygen, O₂.

Question 9

What is the word equation for photosynthesis?

Answer 9

carbon dioxide + water → glucose + oxygen

Question 10

What is the chemical equation for photosynthesis?

Answer 10

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Question 11

Why did the amount of carbon dioxide decrease in the atmosphere?

Answer 11

Carbon dioxide was taken in by plants (such as algae) and was converted to glucose and oxygen. The carbon in glucose, C₆H₁₂O₆, is kept inside the plant material. After millions of years, many organisms were buried under mud and sediment in oceans, rivers, and swamps.

Question 12

What is coal formed from?

Answer 12

Trees and plant matter in swamps. It is classed as a sedimentary rock.

Question 13

What are crude oil and natural gas formed from?

Answer 13

Plankton deposits in mud on ocean seabeds.

Question 14

What is the scientific name for limestone?

Answer 14

calcium carbonate - CaCO₃

Question 15

What happened to methane and ammonia in the atmosphere?

Answer 15

They reacted with the oxygen that was formed by algae.

Question 16

What are the chemical equations for methane and ammonia reacting with oxygen?

Answer 16

CH₄ + 2O₂ → CO₂ + 2H₂O
4NH₃ + 3O₂ → 2N₂ + 6H₂O

Question 17

By what time did our current atmosphere stabilise?

Answer 17

200 million years ago

Question 18

What % of gases make up our current atmosphere?

Answer 18

78% nitrogen
21% oxygen
0.9% argon
0.04% carbon dioxide
0.1% other gases (e.g. Noble Gases, water vapour)

Question 19

What are the 3 main greenhouse gases?

Answer 19

carbon dioxide
methane
water vapour

Question 20

What is the chemical equation for the formation of calcium carbonate (limestone)?

Answer 20

CO₂ + H₂O ⇌ 2H⁺ + CO₃^2-
Ca²⁺ + CO₃^2- → CaCO₃

Question 21

Why is the Earth heated by greenhouse gases?

Answer 21

Greenhouse gases allow short-wavelength electromagnetic radiation (e.g. UV light) to pass through, but it absorbs long-wavelength infrared radiation (thermal). This causes the molecules to vibrate rasing their temperature.

Question 22

What are some consequences of global warming?

Answer 22

• rising sea levels
• climate change
• disruption of ecosystems

Question 23

What does carbon footprint mean?

Answer 23

The total amount of carbon dioxide and other gases produced by an item over its life cycle.

Question 24

How does CCS work?

CCS - Carbon Capture and Storage

Answer 24

Carbon dioxide, formed from fossil fuels, is pumped down to be absorbed by porous rocks; this could be done in old oil fields.

Question 25

What is the advantage of using CCS?

CCS - Carbon Capture and Storage

Answer 25

It would reduce the carbon footprint of fossil fuels.

Question 26

What is the disadvantage of using CCS?

CCS - Carbon Capture and Storage

Answer 26

Increase the total cost of electricity by 10%.

Question 27

What is one impurity found in fossil fuels?

Answer 27

sulfur

Question 28

What is formed when sulfur and oxygen react?

Answer 28

sulfur dioxide

Question 29

How is acid rain formed?

Answer 29

Sulfur dioxide and nitrogen oxides mix with clouds and water to form dilute sulfuric acid and dilute nitric acid.

Question 30

Why do nitrogen oxides rarely form?

Answer 30

Nitrogen is a very unreactive element; there must be high temperatures for it to form.

Question 31

What are two gases that form in the incomplete combustion of fossil fuels?

Answer 31

CO - carbon monoxide
C - carbon particulates (soot)

Question 32

What are the dangers of acid rain?

Answer 32

It can damage buildings (limestone) and corrode metals.

Question 33

What is the cause of smog?

Answer 33

nitrogen oxide, NO_x

Question 34

What can smog cause?

Answer 34

global dimming and respiratory problems

Question 35

How are nitrogen oxides formed?

Answer 35

NO_x are formed from the oxidization of N₂ at high temperatures in combustion.

Question 36

How is sulfur dioxide formed?

Answer 36

SO₂ is formed from the oxidization of sulfur impurities in fossil fuels.

Question 37

What are the five main pollutants in the atmosphere?

Answer 37

CO₂ - carbon dioxide
CO - carbon monoxide
C - carbon particulates (soot)
SO₂ - sulfur dioxide
NO_x - nitrogen oxides

Question 38

What is global dimming?

Answer 38

The decrease of sunlight reaching the earth.