C11- Chemistry of The Earth’s Atmosphere 🌋

Question 1

What are the gases in the atmosphere today ?

Answer 1

• nitrogen
• oxygen
• and, there are also small proportions of various other gases [such as: carbon dioxide, water vapour and the noble gases] in the Earth’s atmosphere today

Question 2

What are the proportion of gases in the Earth’s atmosphere today ?

Answer 2

• approximately 78% to 80% of the Earth’s atmosphere is nitrogen
• and, approximately 20% to 21% of the Earth’s atmosphere is oxygen

Question 3

What is the first stage of the theory, about how the early atmosphere changed into the current atmosphere ?

Answer 3

• one theory suggests that during the first billion years of the Earth’s existence, there was intense volcanic activity that released gases, that formed the early atmosphere and water vapour that condensed to form the oceans.

Question 4

What is the second stage of the theory, about how the early atmosphere changed into the current atmosphere ?

Answer 4

• volcanoes then also produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia.

Question 5

What is the third stage of the theory, about how the early atmosphere changed into the current atmosphere ?

Answer 5

• when the oceans formed, carbon dioxide then dissolved in the water, to form a weak acid.
• carbonates were then precipitated [because the weak acid reacted with minerals in the sea], producing sediments- which reduced the amount of carbon dioxide into the atmosphere

Question 6

What was carbon dioxide in the sea used for ?

Answer 6

• as sediments of carbon rock were formed on the sea bed, some of the carbon dioxide in the sea was used to make corals
• ; some of the carbon dioxide, was also used to make shells of organisms [e.g- mussels]

Question 7

Why can’t chemists be certain about the early atmosphere ?

Answer 7

• chemists [scientists] can’t be certain about the early atmosphere because, the Earth is approximately 4.6 billion years old

Question 8

What were the gases in the Earth’s atmosphere ?

Answer 8

• in the first stage of the Earth’s early atmosphere, the Earth’s atmosphere was thought to be consist of mainly carbon dioxide, with little or no oxygen gas

Question 9

How did the percentage of oxygen in the atmosphere increase ?

Answer 9

• approximately 2.7 billion years ago, photosynthetic algae first evolved in the oceans
• these algae then photosynthesised, which released oxygen into the atmosphere

Question 10

How did the percentage of carbon dioxide in the atmosphere increase ?

Answer 10

• algae and plants decreased the percentage of carbon dioxide, in the atmosphere by photosynthesis
• ; carbon dioxide was also decreased by the formation of sedimentary rocks, and fossil fuels that contained carbon

Question 11

How did oxygen enter the atmosphere ?

Answer 11

• photosynthetic algae produced oxygen, which entered the atmosphere

Question 12

How did animals evolve ?

Answer 12

• over the following billion of years, plants evolved which increased the percentage of oxygen in the atmosphere
• this meant, the percentage of oxygen gradually increased to a level, that allowed animals to evolve

Question 13

What are fossil fuels ?

Answer 13

• fossil fuels, are organic matter [e.g- old plants and animals] that died millions of years ago and have formed into coal, oil or gas over millions of years.

Question 14

How is coal formed ?

Answer 14

• coal is formed from the remains of ferns and trees
• plant remains are covered with sediment and compressed because, a high temperature and pressure creates coal

Question 15

How is crude oil formed ?

Answer 15

• crude oil is formed over millions of years, from the remains of tiny sea creatures called plankton- which were buried in mud
• when plankton die, they settle in mud on the sea-bed and they are compressed by sediment over time
• heat and pressure then convert the plankton into crude oil

Question 16

How is natural gas formed ?

Answer 16

• natural gas is made from deposits of plankton that have died and sunk to the bottom of the sea or the bottom of lakes.
• the plankton was then buried by layers of sediment, which prevented oxidation of the dead material due to a lack of oxygen.
• Over millions of years, the dead plankton has become natural gas.

Question 17

What are coal, crude oil and natural gas all examples of ?

Answer 17

• coal, crude oil and natural gas are all examples of fossil fuels

Question 18

What do all fossil fuels contain ?

Answer 18

• all fossil fuels contain [trapped] carbon that was part of the carbon dioxide taken in by photosynthetic algae and plants, during photosynthesis

Question 19

What does the term ‘greenhouse gases’ mean ?

Answer 19

• greenhouse gases, are gases in the Earth’s atmosphere that trap heat and cause the greenhouse effect

Question 20

What are some examples of greenhouse gases ?

Answer 20

• water vapour
• carbon dioxide
• and, methane

Question 21

What is the first stage of the greenhouse effect ?

Answer 21

• energy from the sun travels to the Earth as short wavelength radiation [e.g- ultraviolet and visible light]

Question 22

What happens after energy from the sun travels to the Earth ?

Answer 22

• some of the short wavelength radiation reflects back into space; most of it easily passes through the atmosphere

Question 23

What happens when some of the short wavelength radiation reflects back into space ?

Answer 23

• the energy of the radiation is then absorbed when it reaches the surface of the Earth

Question 24

What happens when energy reaches the surface of the Earth ?

Answer 24

• the surface of the Earth now radiates the energy as long wavelength radiation [e.g- infra red radiation]

Question 25

What happens after the surface of the Earth radiates energy ?

Answer 25

• some of the long wavelength radiation interacts with the greenhouse gas molecules in the atmosphere
• as the energy is trapped in the atmosphere, this causes the temperature of the atmosphere to increase

Question 26

What does it mean that some of the long wavelength radiation interacts with the greenhouse gas molecules in the atmosphere ?

Answer 26

• this means, energy in the long wavelength radiation is absorbed

Question 27

What happens after some of the long wavelength radiation, interacts with greenhouse gas molecules in the atmosphere ?

Answer 27

• as the energy is trapped in the atmosphere, this causes the temperature of the atmosphere to increase

Question 28

Why do most of the short wavelength radiation, pass through the atmosphere ?

Answer 28

• this is because, short wavelength radiation dosen’t interact strongly with the gas molecules in the atmosphere