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EdExcel GCSE Chemistry > Earth and Atmospheric Science - Topic 8 > Flashcards

Earth and Atmospheric Science - Topic 8 Flashcards

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1
Q

What is thought to have formed the Earth’s early atmosphere?

A
  • the gases (N2 and CO2 gas) produced by volcanic activity are thought to have formed the Earth’s early atmosphere
  • this condensed as it rose into cooler air and then fell as rain - forming the first oceans
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2
Q

When was the Earth thought to have been formed and how?

A
  • 4.5 billion years ago
  • it began as a molten ball of rock and minerals and for its first billions years it was a very violent place
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3
Q

What was the Earth’s early atmosphere thought to contain?

A
  • little or no oxygen
  • a large amount of carbon dioxide
  • some N2 vapour and water vapour
  • small amounts of other gases e.g. CH4, NH4
  • similar to atmosphere on Mars and Venus
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4
Q

What formed the oceans on Earth?

A
  • the gases (N2 and CO2 gas) produced by volcanic activity are thought to have formed the Earth’s early atmosphere
  • as the Earth cooled water vapour cooled and condensed as it rise into cooler air and fell as rainfall - forming the first oceans
  • icy comets also brought water to the Earth and melted as they rained down
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5
Q

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

A
  • amount of carbon dioxide in the atmosphere was decreased when carbon dioxide dissolved as the oceans formed reducing amount of CO2 in atmosphere
  • this formed insoluble carbonate compounds which fell to the bottom and helped to form carbonate rocks
    • carbonates precipitated producing sediment
  • CO2 in atmosphere also decreases as plants evolved to carry out photosynthesis which involved taking in CO2 and producing O2
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6
Q

What did the growth of primitive plants cause?

A
  • the growth of primitive plants used carbon dioxide and released oxygen by photosynthesis
  • consequently the amount of oxygen in the atmosphere gradually increased
  • algae first produced oxygen about 2.7 billion years ago and soon after this
    oxygen appeared in the atmosphere
  • over the next billion years plants evolved and the % oxygen gradually increased
    to a level that enabled animals to evolve
  • algae and plants decreased the % CO2 in the atmosphere by photosynthesis
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7
Q

When did life on Earth begin and what did this life take the form of?

A
  • 3.4 billion years ago
  • this life took the form of simple bacteria-like organisms which could make food for themselves using the breakdown of other chemicals as a source of energy
  • later bacteria and simple organisms such as algae evolved which could use energy of the sun to make their own food in the process of photosynthesis with O2 as a waste product
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8
Q

Photosynthesis equation:

A
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9
Q

What happened when plants evolved and successfully colonised most of the surface of the Earth?

A
  • the atmosphere became increasingly rich in O2
  • as plants had evolved to produce oxygen through photosynthesis
  • conditions now favourable for evolution of animals - organisms which could not make their own food and needed oxygen to respire
  • many of the early microorganisms could not tolerate oxygen (as they had evolved without it) and they largely died out as there were fewer places where they could live
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10
Q

What happens when CO2 is taken up by plants?

A
  • CO2 taken up by plants and turned into new plant material during photosynthesis
  • these animals eat the plant and the C is transferred to the animal tissues, including bones, teeth and shells
  • CO2 trapped in seam animal shells
  • over millions of years ago the dead bodies of huge numbers if these living organisms accumulated at the bottom of the vast oceans where they formed sedimentary carbonate rocks like limestone
  • some were crushed by the movements of the Earth and heated within the crust and they formed fossil fuels e.g. coal
  • this way much of CO2 from the ancient atmosphere became locked up within the Earth’s crust
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11
Q

What happened at the same time of fossil fuels being formed?

A
  • small amounts of NH3 and CH4 remaining in the atmosphere reacted with the oxygen formed by the plants
  • the O2 removed these toxic gases and the levels of N2 and CO2 increased
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12
Q

Why is the balance between CO2 produced and the CO2 which can be absorbed by CO2 sinks is important to maintain?

A

when fossil fuels are burned, C which was locked up 100s of millions of years ago in the tissues of living animals is released as CO2 in the atmosphere

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13
Q

What gases are well-known to be released when fuels are burned?

A
  • carbon monoxide
  • sulfur dioxide
  • oxides of nitrogen
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14
Q

How is carbon monoxide produced?

A

incomplete combustion in a shortage of oxygen

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15
Q

How can carbon monoxide be reduced?

A

converted to CO2 by a catalytic converter

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16
Q

How is sulphur dioxide produced?

A

burning coal or petrol containing sulphur and oxygen

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17
Q

How can sulphur be reduced?

A

removed from power stations by capturing with limestone

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18
Q

How are oxides of nitrogen produced?

A

from N2 and O2 at very high temperatures such as in an engine

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19
Q

How can oxides of nitrogen be reduced?

A

converted to N2 by a catalytic converter

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20
Q

What happens when copper reacts with oxygen (syringe method)?

A
  • when copper is heated it reacts with oxygen
  • in this experiment, 100cm³ of air is going to be passed over some copper turnings that are being heated strongly
  • as the air passes over the copper oxygen in the air will react with the copper
  • by seeing what volume of air remains after the reaction, we can work out the % of oxygen in the air
  • the air will be passed over the hot copper several times to give all the oxygen chance to react
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21
Q

Diagram of experiment to find % of oxygen in the air (syringe method):

A
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22
Q

Method for finding the % of oxygen in the air (syringe method):

A
  1. 100cm³ of air is placed in one of the 100cm³ gas syringes as shown in the diagram above - the other syringe is empty
  2. The air is passed to and fro over the copper turnings which are heated strongly with a Bunsen burner
  3. This is repeated until the volume of air stops decreasing
  4. The apparatus is left for a few minutes to cool down and then the volume is recorded in the table below with data from some other experiments that other classes have done
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23
Q

Results for finding the % of oxygen in the air (syringe method):

A
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24
Q

Why does the volume of air decrease during the experiment (finding the % of oxygen in the air - syringe method)?

A

it decreases as when the air passes over the copper the oxygen in the air will react with the copper decreasing the volume of air in the gas syringe

25
Q

Are there any anomalous results? Explain your answer and state which, if any, are anomalous (finding the % of oxygen in the air - syringe method).

A

experiment 3 has an anomalous result as the other experiments show that % of oxygen in the air is 20-22% but in 3 it is 15%

26
Q

Explain why doing repeats and finding an average is useful (finding the % of oxygen in the air - syringe method):

A
  • to help reduce scope for error → reduce effect of random error so average is closer to real value
  • spot anomalous results - average with anomalies emitted so increases accuracy
  • increases accuracy
27
Q

Is the result accurate (finding the % of oxygen in the air - syringe method)?

A

yes, as it matches the known value for oxygen in the air which is 21%

28
Q

Write a word equation for the reaction between copper and oxygen (finding the % of oxygen in the air - syringe method):

A

copper + oxygen —> copper oxide

29
Q

Was this resolution suitable in this experiment? Explain your answer (finding the % of oxygen in the air - syringe method).

A

No - needed higher resolution to calculate % of oxygen in air, needed smaller increments

30
Q

Explain why you waited for the apparatus to cool down after the experiment before reading the volume of air in the syringe (finding the % of oxygen in the air - syringe method).

A
  • safety precaution
  • when it is hot gas expands so takes up larger volume so needs to cool down for variable to be controlled
  • gas at room temp at start of experiment so should wait for it to cool down to room temp
31
Q

Method to find the proportion of oxygen in the air (finding proportion of oxygen in the air - burning phosphorous):

A
  1. A marked bell jar with its lid removed is placed on top of coins inside a trough
  2. The coins ensure that water can go inside the bell jar
  3. Water is poured into the through until it reaches the level 0 marked on the bell jar
  4. A piece of phosphorous is placed in an evaporating dish which floats on the water
  5. The phosphorous is lit and a lid is placed at the top of the bell jar to cover it
  6. The yellow phosphorous starts burning, and the air space gets filled with white fumes
  7. The white fumes are phosphorous oxide which dissolves in the water forming an acidic solution
  8. When the phosphorous has stopped burning and the white fumes have disappeared the level of water in the bell jar is measured
32
Q

Diagram of experiment to find the proportion of oxygen in the air (finding proportion of oxygen in the air - burning phosphorous):

A
33
Q

Why did the water level go up in the bell jar (finding proportion of oxygen in the air - burning phosphorous)?

A
  • as water displaces the air when oxygen reacts with the phosphorous to form phosphorous oxide which causes internal pressure of bell jar to decrease so water increases to increase and equalise the pressure
  • O2 used up, water in trough sucked up to replace it
34
Q

What evidence does this experiment provide (finding proportion of oxygen in the air - burning phosphorous)?

A
  • experiment tells us that the proportion of oxygen previously in the air (before it reacted with phosphorous oxide)
  • percentage of O2 needed to burn phosphorous
35
Q

If the solution was tested with universal indicator what would happen and why (finding proportion of oxygen in the air - burning phosphorous)?

A
  • turn red
  • go to lower pH as phosphorous oxide dissolves in water making it acidic
  • solution P4O10 produced
36
Q

What happens as CO2 levels go up?

A
  • as CO2 levels go up reaction between CO2 and sea water increases, resulting in the formation of insoluble carbonates (mainly CaCO3) that are deposited as sediment on the bottom of the ocean and soluble hydrogen carbonate (mainly Ca and Mg) which simply remain in solution in the sea water
  • in this way the seas and oceans act as a buffer absorbing excess CO2 but releasing it if necessary
  • buffering system cannot cope quickly enough to deal with the additional CO2 currently being poured into the atmosphere
37
Q

Describe the chemical test for oxygen:

A
  • Uses a glowing splint inserted into a test tube of the gas
  • Glowing splint relights in oxygen
38
Q

How can oxygen be prepared in a laboratory?

A
  • hydrogen peroxide spontaneously decomposes into water and oxygen
  • at room temperature this reaction is very slow and is therefore speeded up using a catalyst such as manganese oxide MnO2
  • reaction is called catalytic decomposition
39
Q

Diagram to show laboratory preparation of oxygen:

A
40
Q

Word equation for laboratory preparation of oxygen:

A

hydrogen peroxide ——> water + oxygen

41
Q

Colour of oxygen:

A

colourless

42
Q

Odour of oxygen:

A

odourless

43
Q

Density of oxygen (compared to air):

A

similar density compared to air

44
Q

Solubility of oxygen in water:

A

minimal

45
Q

Effect of oxygen on glowing splint:

A

relights glowing splint

46
Q

Effect of oxygen on universal indicator:

A
  • no change
  • neutral
47
Q

What is the greenhouse effect?

A
  • various gases in the atmosphere inc. CO₂, CH₄ and water vapour, absorb heat radiated from the Earth
  • subsequently this releases energy which keeps the Earth warm (essential for life on Earth)
  • But some heat is radiated from the Earth as infrared radiation
  • Some of this IR radiation is absorbed by greenhouse gases in the atmosphere
  • Atmosphere warms up leading to the greenhouse effect and global warming
48
Q

What sort of radiation does the sun emit?

A
  • radiation from the sun is of short wavelength
  • it can pass through the atmosphere and not be absorbed by the atmospheric gases
49
Q

What do the gases in the atmosphere do?

A
  • greenhouse gases keep the Earth warm by trapping heat
  • the gases in the atmosphere allow short wavelength radiation to pass through the atmosphere to the Earth’s surface
  • the gases then absorb the outgoing long wavelength radiation from the Earth, causing an increase in temperature
  • the temperature increase is beneficial to us as the temperature of the Earth is being kept relatively stable as GHG’s trap heat
  • even though the temperature at the polar caps gets very low and the temperature at the equator can get very high, between these limits life can be sustained
  • both our moon and other planets experience temperatures way outside these limits
50
Q

What may an increase in greenhouse gases cause?

A
  • light (radiation) is emitted from the Sun
    • some of the radiation from the Sun is reflected by the atmosphere and goes back into space
    • some of this is changed into heat when it reaches Earth - surface is warmed
  • some of heat energy (radiation) absorbed by the Earth is radiated from the earth
    • some radiation from the Earth goes back into space
    • some radiation from Earth is reflected by clouds - greenhouse gases trap the heat around the Earth - surface is warmed
    • a gradual build-up of carbon dioxide and methane means less of the heat reflected escapes into space - the Earth’s temperature increases as more heat is trapped by GHG’s in the Earth’s atmosphere due to the increase in GHG’s
51
Q

Human activities that affect CO₂ levels:

A
  • combustion of fossil fuels
  • deforestation
  • driving
  • consuming electricity
52
Q

Human activities that affect CH₄ levels:

A
  • animal farming (through digestion and decomposition of waste) e.g. raising livestock cows
  • decomposition of rubbish in landfill sites
53
Q

Why would deforestation lead to increased levels of CO₂?

A
  • trees produce O₂ and take in CO₂
  • if we reduce the number of trees in the world by large amounts this have an effect on CO₂ levels in the world
54
Q

Consequences of climate change/global warming/the greenhouse effect:

A
  • sea levels rising causing flooding and coastal erosion
    • more frequent and severe storms in many parts of the world
    • changes in the amount, timing and distribution of rainfall
  • in some regions impacts of climate change are already changing lives e.g. people of the Arctic region where ice sheet are melting
55
Q

Predicted consequences of climate change/global warming/the greenhouse effect:

A
  • temperature stress for humans and wildlife - some areas will become too hot for people to make a living
  • water stress for humans and wildlife - fresh water supplies will reduce in some regions
  • changes in the food producing capacity of some regions - the production of wheat and maize has already been affected
  • changes to the distribution of wildlife species - migration patterns are changing
56
Q

Ways to prevent the amount of greenhouse gases in the atmosphere increasing:

A
  • burn less fossil fuels
  • switch to renewable sources of energy
  • switch to electric cars
  • use renewable energy to fuel homes
  • greater energy efficiency
  • recycle rather than send waste to landfills
57
Q

What do many scientist believe human activities will cause?

A
  • Based on peer-reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth’s atmosphere to increase at the surface and that this will result in global warming/climate change
  • But it is difficult to model such complex systems as global climate change
  • This leads to simplified models, speculation and opinions presented in the media that may be based on only parts of the evidence and which may be biased
58
Q

Why has the amount of O2 in the atmosphere increased since the Earth’s early atmosphere was formed?

A
  • due to and increase in photosynthesising plants that had evolved and grown which took in CO2 and released O2 (process of photosynthesis)
  • this increased the amount of O2 in the atmosphere
59
Q

How have the gases in the atmosphere changed as a result of human effects?

A
  • amounts of CO2 in the atmosphere recently increased due to burning fossil fuels
  • amounts of CO2 increased in recent times due to increase in agricultural farming
  • deforestation means less CO2 is absorbed
  • reforestation means more CO2 is absorbed

EdExcel GCSE Chemistry (29 decks)

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