chemistry of the atmosphere

Question 1

what has been roughly the same for 200 million years

Answer 1

the proportion of different gases in the atmosphere

Question 2

proportions of gases in the atmosphere

Answer 2

• around 80% nitrogen
• around 20% oxygen
• small proportions of other gases including carbon dioxide, water vapour and noble gases e.g., argon

Question 3

why is evidence for the early atmosphere limited

Answer 3

because of the time scale of 4.6 billion years, meaning there’s a lack of evidence

Question 4

theory about volcanic activity

Answer 4

during first billion years of earth’s existence, was intensive volcanic activity that released gases forming early atmosphere and water vapour that condensed to form oceans

Question 5

what does the volcanic activity theory state about the start of the period of the earth’s existence

Answer 5

the earth’s atmosphere may have been like the atmospheres of mars and venus today; mainly carbon dioxide with little or no oxygen

Question 6

what does the volcanic activity theory state about volcanoes producing [ ]

Answer 6

volcanoes produced nitrogen which built up in the atmosphere and there may have been small proportions of methane and ammonia

Question 7

what does the volcanic activity theory propose about when the oceans formed

Answer 7

carbon dioxide dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere

Question 8

how did oxygen increase

Answer 8

algae and plants first produced oxygen about 2.7bil years ago, and produced the oxygen that is now in the atmosphere by photosynthesis

Question 9

how did carbon dioxide decrease

Answer 9

• algae and plants decreased percentage of CO2 by photosynthesis
• decreased by formation of sedimentary rocks and fossil fuels that contain carbon

Question 10

how did the sedimentary rocks that decreased carbon dioxide levels form

Answer 10

as water vapour from volcanoes condensed to form oceans, some co2 dissolved in oceans to form weak acid which reacted with minerals in the sea to form precipitates that formed sediments of carbonate rock on the seabed over time

Question 11

how did the limestone that decreased carbon dioxide levels form

Answer 11

some of the co2 dissolved in the sea which was used to make corals and shells of aquatic organisms like mussels. when these organisms died, they formed limestone

Question 12

how did the coal in the early atmosphere form

Answer 12

formed from remains of ferns and trees; died in marshy wetlands; no oxygen present so do not decay; plant remains covered in sediment and compressed; high temps and pressures cause coal to form

Question 13

how did the crude oil in the early atmosphere form

Answer 13

formed from plankton; no oxygen present so do not decay; get trapped under sediment; heat and sediment cause them to form crude oil

Question 14

how did the natural gas in the early atmosphere form

Answer 14

found near deposits of oils because it is formed from plankton in a similar way to oil

Question 15

what happened as green plants evolved

Answer 15

co2 levels decreasing and oxygen levels increasing to the degree that animals were able to survive and evolve

Question 16

what do greenhouse gases in the atmosphere do

Answer 16

they maintain temperatures on earth high enough to support life

Question 17

name the greenhouse gases

Answer 17

water vapour, carbon dioxide and methane

Question 18

explain how greenhouse gases maintain temperature on our planet

Answer 18

• short wave radiation passes through atmosphere
• earth’s surface re-emits it as long wave radiation
• long wave radiation is absorbed by greenhouse gases which heats the planet up

Question 19

2 human activities that increase the level of CO2

Answer 19

• burning fossil fuels for electricity as they release locked up carbon
• deforestation, as cutting down trees reduces the amount of CO2 absorbed from the atmosphere by photosynthesis

Question 20

2 human activities that increase the level of methane

Answer 20

• cattle reared for humans to eat produce methane
• increase in the number of rice paddy fields

Question 21

what do many scientists believe about human activities

Answer 21

based on peer-reviewed evidence, human activities will are believed to cause the temperature of the earth’s atmosphere to increase at the surface, resulting in global climate change

Question 22

why is their bias surrounding climate change

Answer 22

global climate change is a complex system which is difficult to model. this leads to simplified models, speculation and opinions presented in the media that may be based on only parts of the evidence

Question 23

what is a major cause of climate change

Answer 23

an increase in average global temperature

Question 24

potential effects of global climate change

Answer 24

• flooding; temp increasing means polar ice caps melt, sea levels rise, and flooding of land
• extreme weather; more common and severe, like storms, which causes damage
• changes in rainfall; damage crops, lack of rain causes drought, affects food production
• extinction; if climate changes quickly, animals and plants cannot adapt to environment quick enough so will die out

Question 25

consequences of global climate change

Answer 25

• rising sea levels as glaciers melt bc of high temperatures, causing flooding in low-lying countries
• extinction of species due to the destruction of natural habitats
• migration of species as they will move to areas that are more habitable (no droughts)
• spread of diseases caused by warmer climate
• loss of habitat due to climate change (animals that live on glaciers)
• more droughts and wildfires
• warmer oceans; affects sea life
• stronger storms

Question 26

define carbon footprint

Answer 26

the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event

Question 27

simply, how can the carbon footprint be reduced

Answer 27

by reducing emissions of carbon dioxide and methane

Question 28

methods for reducing carbon footprint

Answer 28

• co2 emissions reduced by using renewable energy supplies instead of fossil fuels
• use public transport instead of private cars
• reduce consumption of meat
• buy locally sourced foods to reduce food mileage
• switching to electric vehicles
• recycling and reusing materials

Question 29

why are actions for reducing carbon footprint potentially limited

Answer 29

• resistance on an individual level as people don’t tend to want to change their ways
• lack of investment schemes
• alternative technologies are still in their infancy
• governments tend to be slow to act on issues as they fear negative impact on their economies

Question 30

what is a major source of atmospheric pollutants

Answer 30

the combustion of fuels

Question 31

what do most fuels contain

Answer 31

carbon and/or hydrogen, and may also contain some sulfur

Question 32

what can also be released in combustion reactions

Answer 32

solid particles and unburned hydrocarbons that form particulates in the atmosphere

Question 33

what are the gases released into the atmosphere when a fuel is burned

Answer 33

may include carbon dioxide, water vapour, carbon monoxide, sulfur dioxide and oxides of nitrogen

Question 34

what is complete combustion

Answer 34

there is enough oxygen in the reaction, so carbon dioxide is produced

Question 35

why is the complete combustion of fuels bad

Answer 35

carbon dioxide is produced, which is an atmospheric pollutant as it is a greenhouse gas that contributes to climate change

Question 36

why is the incomplete combustion of fuels bad

Answer 36

because carbon monoxide is produced, which is a toxic gas that is colourless and odourless, meaning it’s not easily detected; reduces body’s ability to carry blood

Question 37

products of complete combustion

Answer 37

carbon dioxide + water

Question 38

products of incomplete combustion

Answer 38

carbon monoxide + water

Question 39

how is sulfur dioxide produced from fuels

Answer 39

some fuels such as coal contain sulfur impurities, and, when the fuel is burned, the sulfur atoms are oxidised to produce sulfur dioxide gas

Question 40

how are oxides of nitrogen produced from fuels

Answer 40

they are produced inside engines because the temps and pressures are so high that the nitrogen and oxygen in the air react together to form nitrous oxides

Question 41

why is sulfur dioxide and oxides of nitrogen bad

Answer 41

they can cause respiratory problems in humans and cause acid rain; destroys trees, kills fish, corrodes buildings made of limestone

Question 42

how are particulates (soot) produced from fuels

Answer 42

incomplete combustion

Question 43

why are particulates bad

Answer 43

they cause global dimming and health problems for humans e.g., lung cancer, asthma attacks