C13 The Earth's Atmosphere

Question 1

what are the gases in the atmosphere today and their percentage presence?

Answer 1

nitrogen - around 78%
oxygen - around 21%
small amounts of noble gases, carbon dioxide and methane

Question 2

why can scientists not be certain of the early atmosphere?

Answer 2

the earth is very old (4600 million years old)

Question 3

what do scientists think happened in the first billion years of the earth?

Answer 3

there was intense volcanic activity which released the gases that form the atmosphere (including water vapour)

Question 4

what happened to the water vapour in the atmosphere when the earth cooled?

Answer 4

the water vapour condensed to become the oceans

Question 5

what did the earth’s atmosphere consist of in the early stages?

Answer 5

mainly carbon dioxide with little or no oxygen

there was also small but increasing amount of nitrogen

Question 6

what other gases did volcanoes release?

Answer 6

nitrogen
ammonia
methane

Question 7

what happened to carbon dioxide in oceans?

Answer 7

some of it dissolved to form a weak acid
this reacted with minerals in the sea to form precipitates
over time, this formed sediments of carbonate rock on the sea bed

Question 8

what was carbon dioxide used for in organisms?

Answer 8

to make corals and shells of organisms - when they died, this formed sedimentary rock on the sea bed

Question 9

where did the oxygen in the atmosphere come from?

Answer 9

photosynthetic algae evolved
the photosynthesis produced oxygen
more plants evolved and produced more oxygen

Question 10

what is the word equation for photosynthesis?

Answer 10

carbon dioxide + water –light–> glucose + oxygen

Question 11

what is the symbol equation for photosynthesis?

Answer 11

6CO2 + 6H2O —> C6H12O6 + 6O2

Question 12

are fossil fuels renewable?

Answer 12

NO

Question 13

what is coal formed from?

Answer 13

the remains of ferns and trees

Question 14

what happens if trees/ferns die in marshy wetlands?

Answer 14

there is a lack of oxygen or acidic conditions which mean the trees do not decompose

Question 15

what creates coal?

Answer 15

the plant remains are covered by sediment and compressed

the high pressure and temperature

Question 16

what is crude oil formed from?

Answer 16

plankton in the sea

Question 17

how is crude oil formed?

Answer 17

if plankton dies and there is no oxygen, they do not decompose
they then get compressed by sediment over time
heat and pressure cause it to become crude oil

Question 18

what is natural gas formed from?

Answer 18

plankton in a similar way to oil

Question 19

what do all fossil fuels contain?

Answer 19

trapped carbon from the carbon dioxide in photosynthesis

Question 20

name some greenhouse gases:

Answer 20

water vapour
methane
carbon dioxide

Question 21

describe how the greenhouse effect works:

Answer 21

Energy from the sun travels to the Earth as short wavelength radiation.
Some of the radiation is reflected off the atmosphere but most passes through.
This happens because short wavelength radiation does not interact strongly with the gas molecules in the atmosphere.
The energy is now absorbed when it reaches the surface of the earth.
The surface of the Earth now radiates the energy as long wavelength radiation
Some of the long wavelength radiation now interacts with (the energy is absorbed by) the greenhouse gas molecules.
The energy is now trapped in the atmosphere so the temperature increases.

Question 22

what is the advantage of the greenhouse effect?

Answer 22

it keeps the temperature of the atmosphere warm enough to support life

Question 23

why are the levels of carbon dioxide and methane increasing?

Answer 23

it is due to human activity

Question 24

how are carbon dioxide levels increasing?

Answer 24

burning fossil fuels

deforestation - burning fields for grazing

Question 25

how are the levels of methane increasing?

Answer 25

agriculture - growing rice in flooded paddy fields

cattle - when cows pass wind

Question 26

how does the temperature of the atmosphere increase due to CO2 and methane?

Answer 26

more of the sun’s energy is trapped in the atmosphere

Question 27

what effects does rising temperatures cause?

Answer 27

• increase melting of polar ice sheets and glaciers. this will increase sea levels
• more severe weather
• change the distribution of animals. this could change the levels of insect born diseases

Question 28

what will increases in sea levels cause?

Answer 28

it could lead to more flooding of low lying areas

Question 29

why do scientists think that climate change is caused by human activity?

Answer 29

the evidence was shared between many different scientists

they can then criticise the evidence and decide if it is valid

Question 30

what is the problem with understanding climate change?

Answer 30

climate change is complex and difficult to model

this means stories can be biased or too simplified

Question 31

what are some uncertainties about climate change?

Answer 31

we cannot predict with certainty how much the temperature will increase which can lead to speculation in the media

Question 32

what is carbon footprint?

Answer 32

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

Question 33

how can carbon dioxide emissions be reduced?

Answer 33

insulation in homes
public transport
renewable sources of electricity
energy saving in the home (e.g. energy saving light bulbs)

Question 34

what is the problem with reducing carbon foodprint?

Answer 34

expensive and people are reluctant to pay

inconvenient

Question 35

how can methane emissions be reduced?

Answer 35

eat less beef and dairy products

trap methane produced by landfills and burning it to produce electricity

Question 36

what is a fuel?

Answer 36

a substance which releases energy when combusted

Question 37

what is complete combustion?

Answer 37

when a fuel is completely oxidised

Question 38

what is produced when a hydrocarbon is completely combusted?

Answer 38

carbon dioxide and water

Question 39

what is produced when a hydrocarbon is incompletely combusted?

Answer 39

carbon monoxide and water

Question 40

what is incomplete combustion?

Answer 40

when a fuel is not completely oxidised as there is not enough oxygen

Question 41

what happens when there are sulfur impurities in a fuel?

Answer 41

when it is burned, the sulfur atoms are oxidised to form sulfur dioxide

Question 42

how are oxides of nitrogen produced?

Answer 42

high temperatures in engines cause nitrogen to react with oxygen from the air
this produces a range of different molecules so they are called oxides of nitrogen (NOx)

Question 43

what can sulfur dioxide and NOx cause?

Answer 43

breathing problems in humans

they dissolve in rainwater to form acid rain - this can damage trees and corrode stone buildings

Question 44

what are particulates?

Answer 44

particles of carbon and unburned hydrocarbons

Question 45

what can particulates cause?

Answer 45

damage to human health
global dimming (amount of energy that reaches the earth from the sun)