chemistry of the atmosphere

Question 1

what does the Earth's atomsphere consist of today
give proportions of
nitrogen
oxygen
and other gases

Answer 1

78 percent nitrogen
21 percent oxygen
1 percent other gases such as carbon dioxide water vapour and argon

Question 2

why can’t sure about the Earth’s early atmosphere

Answer 2

because the Earth formed 4.6 billion years ago

Question 3

what do scientists believe caused the earth’s early atmosphere

Answer 3

intense volcanic activity

volcanoes released gases that formed the atmosphere

Question 4

volanic activity released gases that formed atmosphere
one of these was water vapour
explain water vapour

Answer 4

As earth cooled, water vapour condensed to form the oceans. volcanoes also released huge amounts of carbon dioxide

Question 5

intense volcanic activity released gases that formed Earth’s early atmosphere
these gases included water vapour which condensed to form the oceans but volcanoes also released huge amounts of carbon dioxide
so at the early stage, what did the earth’s atmosphere consist of

Answer 5

-mainly carbon dioxide with virtually no oxygen

Question 6

what planets today was the Earth’s early atmosphere similar to

Answer 6

mars and venus

Question 7

As well as releasing water vapour and huge amounts of carbon dioxide, volcanoes also released nitrogen which built up in the atmosphere
what two other small amounts of gases were released by volcanoes:

Answer 7

ammonia and methane

Question 8

differences between Earth’s early atmosphere and the atmosphere of the Earth today:

Answer 8

Early atmosphere contained large amounts of carbon dioxide but atmosphere today only contains small amounts
-early atmosphere contained small amount of nitrogen whereas today 78 percent of the atmosphere is nitrogen
Early atmosphere contained very little oxygen whereas today 21 percent of the atmosphere is oxygen

Question 9

how did these changes in atmosphere happen

Answer 9

• water vapour released from intense volcanic activity condensed to form the oceans as the earth cooled
• some of the carbon dioxide dissolved in the oceans to form a weak acid which reacted with minerals in the sea forming precipitates
• overtime these precipitates formed sediments of carbonate rock on the seabed

Question 10

how did carbon dioxide levels decrease

Answer 10

-water vapour released from volcanic activity condensed to form oceans
-carbon dioxide dissolved in the sea to form weak acid which reacted with sea minerals to form precipitates
over time the precipitates formed sediments of carbonate rock on the sea bed
some of the carbon dioxide in the sea was used to make shells of organisms such as mussels and coral
when these died they formed sedimentary rock limestone.
this removed co2 from the atmosphere

Question 11

how did oxygen levels increase

Answer 11

around 2.7 billion years ago, photosynthetic algae first evolved in the oceans. photosynthesis produced oxygen which entered the atmosphere.
plants began to evolve this increased amount of oxygen in the atmospehere.
the level of oxygen reached a point where animals could evolve.
photosynthesis takes in carbon dioxide and this carbon dioxide was locked in fossil fuels

Question 12

fossil fuels

list the three fossil fuels

Answer 12

• coal
• oil
• gas

Question 13

recap point- the early atmosphere contained large amounts of co2 but virtually no oxygen today the earth’s atmospehere contains plenty of oxygen but small amounts of co2.
photosynthesis takes in carbon dioxide and produces oxygen
some of that carbon dioxide can be locked into fossil fuels
list the three

Answer 13

coal oil gas

Question 14

fossil fuels formed over millions of years

they are non renewable is we keep using them they will…..

Answer 14

run out eventually

Question 15

how is coal formed

Answer 15

coal is formed from the remains of ferns and trees
these die in marshy wetlands and do not decompose due to two factors
lack of oxygen and acidic conditions
(both those factors prevent bacteria from carrying out decomposition)
overtime, the plant remains are covered with sediment and compressed
high temperatures and pressures creates coal

Question 16

how is crude oil formed

Answer 16

crude oil is formed from plankton which are tiny plants and animals found in the sea
when plankton die they settle in mud on the seabed
if oxygen is not present then they do not decompose
overtime they become compressed by sediment
heat and pressure converts them into crude oil

Question 17

how is natural gas formed

Answer 17

natural gases can be hydrocarbons or methane

often found near oil deposits that is because natural gas is formed from plankton in a similar way to oil

Question 18

all fossil fuel contains trapped carbon
that carbon was part of carbon dioxide taken in by photosynthesis
algae and plants decreased percentage of co2 in the atmosphere by photosynthesis but whta else decreased carbon dioxide levels

Answer 18

carbon dioxide was also decreased by formation of sedimentary rocks and fossil fuels that contain carbon

Question 19

what are coal and hydrocarbons used for

Answer 19

coal- used to generate electricity

hydrocarbon- used to power vehicles such as cars

Question 20

most fuels including both coal and hydrocarbons contain the elements carbon and hydrogen
when we burn these fuels the carbon and hydrogen atoms react with oxygen in the air

Answer 20

the elements are oxidised

Question 21

methane is found in natural gas and used to heat homes
carbon atoms in methane molecules are oxidised to form carbon dioxide
what are hydrogen atoms oxidised to form

Answer 21

-water vapour

Question 22

what is needed for complete combustion to occur

Answer 22

a good supply of oxygen

Question 23

carbon dioxide is a greenhouse gas .

when can carbon dioxide be released

Answer 23

when humans burn fuels this releases carbon dioxide

Question 24

how does carbon dioxide affect the environment

Answer 24

• its a greenhouse gas

- it contributes to climate change

Question 25

carbon monoxide is a product of incomplete combustion what is the problem with carbon monoxide

Answer 25

its a toxic gas which is odourless and colourless so cannot be really detected

Question 26

some fuels such as coal contain sulphur when coal is burned, sulfur atoms are oxidised

Answer 26

react with oxygen when coals burnt sulphur atoms oxidised producing gas sulfur dioxide

Question 27

sulphur dioxide and oxides of nitrogen cause respiratory problems and acid rain

Answer 27

acid rain damages trees and corrodes limestone buildings

Question 28

particulates cause global dimming how

Answer 28

reduce amount of energy from the sun that reaches the earths surface
global dimming can affect rainfall patterns particulates can also cause health problems such as increasing risk of lung disease and heart disease

Question 29

how are oxides of nitrogen produced

Answer 29

they are produced inside engines

high temperatures cause nitrogen and oxygen from air react this produces a range of molecules called oxides of nitrogen.

Question 30

4.9.1.1 SPECIFICATION POINTS the proportion of different gases in the Earth’s atmosphere

Answer 30

for 200 million years, the proportions of different gases in the Earth’s atmosphere have been much the same as they are today:
about 80 percent is nitrogen
about 20 percent is oxygen
small proportions of other gases including carbon dioxide, water vapour and noble gases such as argon

Question 31

4.9.1.2 THE EARTHS EARLY ATMOSPHERE

Answer 31

-evidence for the Earth’s early atmosphere is limited as the earth was formed 4.6 billion years ago
one theory suggests that there was intense volcanic activity on the Earth that released gases that formed the earth’s early atmosphere and water vapour condensed to form the oceans.At the start of this period the Earth’s atmosphere may have been similar to Mars and Venus consisting of mainly carbon dioxide with little or no oxygen
volcanoes also released nitrogen which gradually built up in the earth’s atmosphere and there may have been small amounts of ammonia and methane
when the oceans formed carbon dioxide dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere

Question 32

4.9.1.3 How oxygen increased specification points

Answer 32

algae and plants produced oxygen that is now in the atmosphere by photosynthesis
algae first evolved 2.7 billion years ago and soon after this oxygen appeared in the atmosphere. over the next billion years,plants evolved and percentage of oxygen gradually increased to a level that enabled animals to evolve.

Question 33

4.9.1.4 How carbon dioxide decreased

Answer 33

algae and plants photosynthesised, which decreased amount of carbon dioxide in the atmosphere, as photosynthesis takes in co2 from the atmosphere
carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contained locked up carbon.

Question 34

4. 9.3 Atmospheric pollutants specification points

4. 9.3.1 atmospheric pollutants from fuels

Answer 34

-a major source of atmospheric pollutants is the combustion of fuels
most fuels, containing coal, carbon and hydrogen may also contain sulfur.
the gases released into the atmosphere when a fuel is burned may include carbon dioxide, water vapour, carbon monoxide sulfur dioxide and oxides of nitrogen . solid particles and unburned hydrocarbons may also be released that form particulates in the atmosphere.
this can cause global dimming, as particulates can reduce the amount of energy from the sun that reaches the Earth’s surface .
-global dimming can also affect rainfall patterns.
particulates can also cause health problems such as increasing the risk of heart and lung cancer

Question 35

4.9.3.2 PROPERTIES AND EFFECTS OF ATMOSPHERIC POLLUTANTS

Answer 35

Carbon monoxide is a toxic, odourless, and colourless gas which is hard to detect.
sulfur dioxide and oxides of nitrogen can cause respiratory problems and acid rain which damages trees and corrodes limestone buildings.
particulates cause health problems and global dimming as particulates reduce the amount of energy from the sun reaching the earths surface.
global dimming can also affect rainfall patterns