Unit 2.4 Resources Flashcards
(119 cards)
0
Q
Why can the incoming radiation from the sun pass straight through the Earth’s atmosphere?
A
It is relatively unaffected by the gases in the Earth’s atmosphere
1
Q
Where does Earth receive most of its energy from?
A
The Sun, in the form of electromagnetic radiation
2
Q
Once the radiation has passed through to the Earth’s surface, what happens to it?
A
- Most is absorbed by the Earth’s surface, warming it
- Some is released back into the atmosphere as longer-wave infrared radiation
3
Q
What happens to the infrared radiation that is emitted by the Earth’s surface?
A
Most goes back into space
But certain gases in the atmosphere absorb some of this infrared radiation:
- It is then re-emitted as energy
- Some passes back towards the Earth
- This traps much of the heat in the lower atmosphere
4
Q
What is the greenhouse effect?
A
The process in which the absorption and subsequent emission of infrared radiation by atmospheric gases warms the lower atmosphere and the planet’s surface
5
Q
Why does the greenhouse effect maintain a steady temperature?
A
It creates an equilibrium:
- The Earth’s surface and atmospheric gases absorbs energy at the same rate as it radiates energy
6
Q
What are the 3 most abundant greenhouse gases?
A
Water vapour
Carbon dioxide
Methane
7
Q
Where does the water vapour in the atmosphere come from?
A
From evaporation of lakes and oceans
8
Q
Where does the carbon dioxide in the atmosphere come from?
A
Volcanic eruptions
Respiration of animals
Burning or decay of organic matter, such as plants
9
Q
Where does the methane in the atmosphere come from?
A
Emitted during the production of coal, natural gas and oil
A product of rotting organic waste in landfill sites
Released from certain animals as a by-product of digestion
10
Q
How do gases absorb radiation?
A
- Certain bonds absorb infrared radiation (such as O-H, or C-H)
- This causes the molecule to vibrate
- Eventually, the vibrating molecule emits of this energy in the form of radiation
- This can then be absorbed by another greenhouse gas molecule or at the Earth’s surface
11
Q
What does the greenhouse effect of a gas depend on?
A
- Its concentration in the atmosphere
- Its ability to absorb infrared radiation
12
Q
What effects is global warming having?
A
- Rivers overflow due to excessively heavy rainfall and melting glaciers. In other areas, drought-like conditions lead to water shortages
- In some regions, longer growing seasons improve crop yields, whereas others experience drought and disease resulting in disastrous harvests
- Storms and hurricanes are becoming more extreme
- Sea ice in the Arctic is melting faster each year. There are fears that the Gulf Stream current may be shut off, leading to severe winters in Northern Europe
- Increasing temps expand the water in the oceans. Together with extra water from melting land ice, sea levels are rising.
13
Q
Why is carbon capture and storage (CCS) useful?
A
It is an immediate strategy to get rid of waste carbon dioxide gas
14
Q
How does CCS do?
A
- It captures carbon dioxide from power stations and stores it away safely, instead of it being released into the atmosphere.
- The Earth has many safe, stable areas in which we can store gases that we don’t want
15
Q
How does CCS work?
A
A decarbonised fuel will be produced by reforming natural gas into a mixture of H2 and CO2:
CH4 + 2H2O ———> CO2 + 4H2
The CO2 will then be separated and piped offshore to an oilfield which is nearing the end of its productive life.
16
Q
How else could carbon be stored?
A
In stable minerals:
- CO2 would be trapped by converting it into a carbonate rock
- It is reacted with metal oxides to produce stable carbonates
17
Q
What is the troposphere?
A
The lowest layer of the Earth’s atmosphere, extending from the Earth’s surface up to about 7km (above the poles) and to about 20km (above the tropics)
18
Q
How is ozone bad for the environment?
A
Ozone near to the Earth’s surface in the troposphere is an air pollutant with harmful effects on the respiratory systems of animals
19
Q
How is ozone good for the environment?
A
Ozone in the upper atmosphere in the stratosphere protects living organisms by preventing harmful ultraviolet light from reaching the Earth’s surface
20
Q
What is the stratosphere?
A
The second layer of the Earth’s atmosphere, containing the ‘ozone layer’, about 10km to 50km above the Earth’s surface
21
Q
Where is the ozone layer found?
A
In the stratosphere, about 10-50km above the Earth’s surface
22
Q
What does the ozone layer filter out?
A
- Ultraviolet radiation from the Sun has wavelengths in the range 270-400nm
- The ozone layer filters out the shorter wavelengths (less than 320nm)
23
Q
Why is the ozone layer at a higher temperature than other parts of the upper atmosphere?
A
- It converts the shorter wavelengths of UV radiation into heat
- This heat is released into the ozone layer, warming it
24
What are the 3 different types of UV radiation?
- UV-a (320-400nm)
- UV-b (280-320nm)
- UV-c (200-280nm)
25
What is the effect of UV-a radiation?
- Reaches the Earth's surface
- It has less energy than the shorter wavelengths and is not as damaging
- Doesn't cause us too much concern
26
What is the effect if UV-b radiation?
Although ozone screens out most UV-b, some does reach the Earth's surface:
- Can cause sunburn
- Can sometimes cause genetic damage
- This can result in skin cancer, if exposure to UV-b is prolonged
27
What effect does UV-c have?
None - it is entirely screened out by the ozone layer
28
How is ozone formed?
- O2 molecules absorb UV radiation with a wavelength of less than 240nm (high-energy radiation)
- This breaks the O2 molecule into 2 oxygen atoms
- The O atoms then react with O2 molecules to form ozone molecules, O3
- This process generates heat
- The heat is absorbed by air molecules in the stratosphere, raising the temperature
29
How does the ozone layer work?
- The ozone molecules formed absorb UV with wavelengths between 240 and 310 nm
- This converts O3 molecules back to O2 molecules and O atoms
- Chemically, this is the reverse of the reaction that forms ozone
- The atomic oxygen, O, produced immediately reacts with other O2 molecules to reform ozone
- And so the cycle continues
- In this way, the chemical energy released when O and O2 combine is converted into heat energy
- The overall effect is to convert penetrating UV radiation into heat, without any net loss of ozone
- This cycle keeps the ozone layer in a stable balance
- A natural steady rate is reached in which ozone is being formed at the same rate as it is being broken down
- It is this process that protects living organisms from the harmful effects of high-energy UV radiation
30
How is ozone removed?
When an oxygen atom and an ozone molecule combine, they form 2 O2 molecules
31
Why is the removal rate of ozone slow?
- The concentration of O atoms is very low
| - But human activity can affect this balance
32
What is the Ozone Depletion Potential (ODP) of a substance?
The relative amount of breakdown to the ozone layer caused by the substance
33
What effect can the introduction of new compounds into the environment have?
It can lead to ozone loss and disruption of the natural equilibrium
34
Where have most of the chlorine radicals in the stratosphere come from?
- They are generated by human activity
| - They have mainly come from chlorofluorocarbons, CFCs
35
How are CFCs broken down?
- They are very stable
- So they can only be broken down by the extremely energetic UV radiation found above most of the ozone layer
- Initiation step: a C-Cl bond is broken when UV radiation strikes a CFC molecule, producing a chlorine radical, Cl•
- Propagation step 1: the chlorine radical is extremely reactive, so it can react with an O3 molecule, breaking it apart and destroying the ozone, producing ClO• and O2
- Propagation step 2: The ClO• then reacts with an oxygen atom, to produce another chlorine radical and O2
- This chlorine radical is free to attack another ozone molecule
- So the 2 propagation steps repeat in a cycle many thousands of times
36
What atmospheric pollutants does the internal combustion engine in a modern car emit?
- Carbon monoxide
- Oxides of nitrogen
- Unburnt hydrocarbons
37
Why is carbon monoxide pollution bad for humans?
- Carbon monoxide can bind strongly to haemoglobin in the blood, reducing the amount of oxygen supplied to tissues and organs
- The heart and brain are severely affected
38
How is carbon monoxide released into the atmosphere?
From the incomplete combustion of hydrocarbons and other organic compounds
39
How are oxides of nitrogen produced in the internal combustion engine?
- During the burning of fuels, air is drawn intro the cylinder along with the fuel
- The fuel is burned in the presence of oxygen, generating energy
- Nitrogen oxides are also produced during this high-temperature process, because some of the nitrogen from the air is oxidised by the oxygen
- 2 oxides of nitrogen are produced: nitrogen monoxide and nitrogen dioxide
40
What effect does nitrogen dioxide have on the environment?
- It can be converted into nitric acid, a contributor to acid rain
- It can react with unburnt hydrocarbons to form low-level ozone
- The mechanism leading to ozone formation involves radicals
- Low-level ozone is a serious pollutant, causing breathing difficulties and increasing susceptibility to infections
41
What provides the energy for the reaction of unburnt hydrocarbons and nitrogen dioxide to produce low-level ozone?
Sunlight
42
Why does the concentration of low-level ozone build up on humid sunny days?
The still air contains large quantities of hydrocarbons and oxides of nitrogen
43
What is the catalytic converter made from?
- It is made from platinum, rhodium and palladium
- It is supported on a honeycomb mesh
- The honeycomb arrangement provides a large surface area
44
How does the catalytic converter work?
- Hot exhaust gases pass over the catalytic surface and the harmful gases are converted into less harmful products
- These are then released into the atmosphere
45
What are the 2 different types of catalytic converters?
Oxidation catalyst
| 3-way catalyst
46
Why is an oxidation catalyst used?
- It is used on diesel engines
- Decreases emissions of carbon monoxide and unburnt hydrocarbons
- It can also remove particulate matter and nitrogen oxides, when combined with complex filter systems
47
Why is a 3-way catalyst used?
- It is fitted to petrol engines
| - Nitrogen monoxide reacts with carbon monoxide to form nitrogen and carbon dioxide
48
How does the catalyst work? (In a catalytic converter for cars)
- The CO and NO gas molecules diffuse over the catalytic surface of the metal
- Some of the molecules are held on to the metal surface by adsorption
- Temporary bonds are formed between the catalytic surface and the gas molecules
- These bonds hold the gas molecules in the correct position on the metal surface, where they react together
- After the reaction, the CO2 and N2 products are desorbed from the surface and diffuse away from the catalytic surface
49
Name 6 of the '12 principles of green chemistry'
- Prevention
- Atom economy
- Less hazardous chemical synthesis
- Designing safer chemicals
- Safer solvents and auxiliaries
- Design for energy efficiency
- Use of renewable resources
- Reduce derivatives
- Catalysis
- Design for degradation
- Real-time analysis for pollution prevention
- Inherently safer chemistry for accident prevention
50
Name some philosophies of green chemistry
- Using renewable resources
- Saving money
- Preventing waste
- Maximising atom economy
- Recycling and biodegradability
51
Name 5 uses of carbon dioxide
- In foam
- As a solvent
- For decaffeinated coffee
- For beer
- For dry cleaning
- For chemical synthesis
- For toxic waste treatment
52
What used to be used as the blowing agents to manufacture expanded polystyrene foam?
Chlorofluorocarbons, CFCs
53
How is CO2 used in foam?
- The expanded polystyrene is made porous
- It is expanded with CO2
- They use CO2 waste from industrial and natural sources, so there is no net increase in global CO2
54
What is supercritical carbon dioxide (scCO2)?
- By altering temperature and pressure CO2 can be converted into an unusual state called a supercritical fluid
- The resulting solvent is scCO2
55
What is the critical temperature of scCO2?
31°C
56
Why is CO2 a good solvent?
- Many organic solvents are volatile, flammable or toxic. CO2 is none of these.
- It can be used with materials that wold usually decompose at higher temperatures
57
How can you modify the properties of scCO2?
By controlling the pressure
58
How is CO2 used to decaffeinate coffee?
- scCO2 is used as a solvent
| - The pressure of the scCO2 is adjusted so that only caffeine is removed
59
Why is CO2 a better solvent for decaffeinating coffee?
- The flavouring remains
| - There is no problem with toxicity
60
How is CO2 used in beer?
- It produces the natural fizz
- It can also be used to extract the characteristic flavour of beer from hops
- scCO2 acts as the solvent
61
How can CO2 be used for dry cleaning?
- scCO2 is used as a solvent, together with a wetting agent
| - It removes grease and oil deposits from clothing
62
Why is CO2 a better solvent for dry cleaning?
- Previously, chlorinated hydrocarbons were used
- These solvents are toxic
So scCO2 is a safer solvent
63
How can CO2 be used for toxic waste treatment?
- Many organic compounds dissolve in scCO2
- The solvent's properties are adjusted using a much higher temp and pressure than those used for decaffeination
- This allows toxins to be removed from toxic waste mixtures
64
Why is CO2 good for chemical synthesis?
- There are many possible reactions that can be carried out with scCO2
- It can be used either as a solvent or as one of the reagents
- The ability to control its solvent properties means that the desired product is obtained with fewer co-products
- This means that product separation is simpler
65
What is the troposphere?
The lowest layer of the Earth's atmosphere, extending from the Earth's surface up to about 7km (above the poles) and to about 20km (above the tropics)
66
How is ozone bad for the environment?
Ozone near to the Earth's surface in the troposphere is an air pollutant with harmful effects on the respiratory systems of animals
67
How is ozone good for the environment?
Ozone in the upper atmosphere in the stratosphere protects living organisms by preventing harmful ultraviolet light from reaching the Earth's surface
68
What is the stratosphere?
The second layer of the Earth's atmosphere, containing the 'ozone layer', about 10km to 50km above the Earth's surface
69
Where is the ozone layer found?
In the stratosphere, about 10-50km above the Earth's surface
70
What does the ozone layer filter out?
- Ultraviolet radiation from the Sun has wavelengths in the range 270-400nm
- The ozone layer filters out the shorter wavelengths (less than 320nm)
71
Why is the ozone layer at a higher temperature than other parts of the upper atmosphere?
- It converts the shorter wavelengths of UV radiation into heat
- This heat is released into the ozone layer, warming it
72
What are the 3 different types of UV radiation?
- UV-a (320-400nm)
- UV-b (280-320nm)
- UV-c (200-280nm)
73
What is the effect of UV-a radiation?
- Reaches the Earth's surface
- It has less energy than the shorter wavelengths and is not as damaging
- Doesn't cause us too much concern
74
What is the effect if UV-b radiation?
Although ozone screens out most UV-b, some does reach the Earth's surface:
- Can cause sunburn
- Can sometimes cause genetic damage
- This can result in skin cancer, if exposure to UV-b is prolonged
75
What effect does UV-c have?
None - it is entirely screened out by the ozone layer
76
How is ozone formed?
- O2 molecules absorb UV radiation with a wavelength of less than 240nm (high-energy radiation)
- This breaks the O2 molecule into 2 oxygen atoms
- The O atoms then react with O2 molecules to form ozone molecules, O3
- This process generates heat
- The heat is absorbed by air molecules in the stratosphere, raising the temperature
77
How does the ozone layer work?
- The ozone molecules formed absorb UV with wavelengths between 240 and 310 nm
- This converts O3 molecules back to O2 molecules and O atoms
- Chemically, this is the reverse of the reaction that forms ozone
- The atomic oxygen, O, produced immediately reacts with other O2 molecules to reform ozone
- And so the cycle continues
- In this way, the chemical energy released when O and O2 combine is converted into heat energy
- The overall effect is to convert penetrating UV radiation into heat, without any net loss of ozone
- This cycle keeps the ozone layer in a stable balance
- A natural steady rate is reached in which ozone is being formed at the same rate as it is being broken down
- It is this process that protects living organisms from the harmful effects of high-energy UV radiation
78
How is ozone removed?
When an oxygen atom and an ozone molecule combine, they form 2 O2 molecules
79
Why is the removal rate of ozone slow?
- The concentration of O atoms is very low
| - But human activity can affect this balance
80
What is the Ozone Depletion Potential (ODP) of a substance?
The relative amount of breakdown to the ozone layer caused by the substance
81
What effect can the introduction of new compounds into the environment have?
It can lead to ozone loss and disruption of the natural equilibrium
82
Where have most of the chlorine radicals in the stratosphere come from?
- They are generated by human activity
| - They have mainly come from chlorofluorocarbons, CFCs
83
How are CFCs broken down?
- They are very stable
- So they can only be broken down by the extremely energetic UV radiation found above most of the ozone layer
- Initiation step: a C-Cl bond is broken when UV radiation strikes a CFC molecule, producing a chlorine radical, Cl•
- Propagation step 1: the chlorine radical is extremely reactive, so it can react with an O3 molecule, breaking it apart and destroying the ozone, producing ClO• and O2
- Propagation step 2: The ClO• then reacts with an oxygen atom, to produce another chlorine radical and O2
- This chlorine radical is free to attack another ozone molecule
- So the 2 propagation steps repeat in a cycle many thousands of times
84
What atmospheric pollutants does the internal combustion engine in a modern car emit?
- Carbon monoxide
- Oxides of nitrogen
- Unburnt hydrocarbons
85
Why is carbon monoxide pollution bad for humans?
- Carbon monoxide can bind strongly to haemoglobin in the blood, reducing the amount of oxygen supplied to tissues and organs
- The heart and brain are severely affected
86
How is carbon monoxide released into the atmosphere?
From the incomplete combustion of hydrocarbons and other organic compounds
87
How are oxides of nitrogen produced in the internal combustion engine?
- During the burning of fuels, air is drawn intro the cylinder along with the fuel
- The fuel is burned in the presence of oxygen, generating energy
- Nitrogen oxides are also produced during this high-temperature process, because some of the nitrogen from the air is oxidised by the oxygen
- 2 oxides of nitrogen are produced: nitrogen monoxide and nitrogen dioxide
88
What effect does nitrogen dioxide have on the environment?
- It can be converted into nitric acid, a contributor to acid rain
- It can react with unburnt hydrocarbons to form low-level ozone
- The mechanism leading to ozone formation involves radicals
- Low-level ozone is a serious pollutant, causing breathing difficulties and increasing susceptibility to infections
89
What provides the energy for the reaction of unburnt hydrocarbons and nitrogen dioxide to produce low-level ozone?
Sunlight
90
Why does the concentration of low-level ozone build up on humid sunny days?
The still air contains large quantities of hydrocarbons and oxides of nitrogen
91
What is the catalytic converter made from?
- It is made from platinum, rhodium and palladium
- It is supported on a honeycomb mesh
- The honeycomb arrangement provides a large surface area
92
How does the catalytic converter work?
- Hot exhaust gases pass over the catalytic surface and the harmful gases are converted into less harmful products
- These are then released into the atmosphere
93
What are the 2 different types of catalytic converters?
Oxidation catalyst
| 3-way catalyst
94
Why is an oxidation catalyst used?
- It is used on diesel engines
- Decreases emissions of carbon monoxide and unburnt hydrocarbons
- It can also remove particulate matter and nitrogen oxides, when combined with complex filter systems
95
Why is a 3-way catalyst used?
- It is fitted to petrol engines
| - Nitrogen monoxide reacts with carbon monoxide to form nitrogen and carbon dioxide
96
How does the catalyst work? (In a catalytic converter for cars)
- The CO and NO gas molecules diffuse over the catalytic surface of the metal
- Some of the molecules are held on to the metal surface by adsorption
- Temporary bonds are formed between the catalytic surface and the gas molecules
- These bonds hold the gas molecules in the correct position on the metal surface, where they react together
- After the reaction, the CO2 and N2 products are desorbed from the surface and diffuse away from the catalytic surface
97
Name 6 of the '12 principles of green chemistry'
- Prevention
- Atom economy
- Less hazardous chemical synthesis
- Designing safer chemicals
- Safer solvents and auxiliaries
- Design for energy efficiency
- Use of renewable resources
- Reduce derivatives
- Catalysis
- Design for degradation
- Real-time analysis for pollution prevention
- Inherently safer chemistry for accident prevention
98
Name some philosophies of green chemistry
- Using renewable resources
- Saving money
- Preventing waste
- Maximising atom economy
- Recycling and biodegradability
99
Name 5 uses of carbon dioxide
- In foam
- As a solvent
- For decaffeinated coffee
- For beer
- For dry cleaning
- For chemical synthesis
- For toxic waste treatment
100
What used to be used as the blowing agents to manufacture expanded polystyrene foam?
Chlorofluorocarbons, CFCs
101
How is CO2 used in foam?
- The expanded polystyrene is made porous
- It is expanded with CO2
- They use CO2 waste from industrial and natural sources, so there is no net increase in global CO2
102
What is supercritical carbon dioxide (scCO2)?
- By altering temperature and pressure CO2 can be converted into an unusual state called a supercritical fluid
- The resulting solvent is scCO2
103
What is the critical temperature of scCO2?
31°C
104
Why is CO2 a good solvent?
- Many organic solvents are volatile, flammable or toxic. CO2 is none of these.
- It can be used with materials that wold usually decompose at higher temperatures
105
How can you modify the properties of scCO2?
By controlling the pressure
106
How is CO2 used to decaffeinate coffee?
- scCO2 is used as a solvent
| - The pressure of the scCO2 is adjusted so that only caffeine is removed
107
Why is CO2 a better solvent for decaffeinating coffee?
- The flavouring remains
| - There is no problem with toxicity
108
How is CO2 used in beer?
- It produces the natural fizz
- It can also be used to extract the characteristic flavour of beer from hops
- scCO2 acts as the solvent
109
How can CO2 be used for dry cleaning?
- scCO2 is used as a solvent, together with a wetting agent
| - It removes grease and oil deposits from clothing
110
Why is CO2 a better solvent for dry cleaning?
- Previously, chlorinated hydrocarbons were used
- These solvents are toxic
So scCO2 is a safer solvent
111
How can CO2 be used for toxic waste treatment?
- Many organic compounds dissolve in scCO2
- The solvent's properties are adjusted using a much higher temp and pressure than those used for decaffeination
- This allows toxins to be removed from toxic waste mixtures
112
Why is CO2 good for chemical synthesis?
- There are many possible reactions that can be carried out with scCO2
- It can be used either as a solvent or as one of the reagents
- The ability to control its solvent properties means that the desired product is obtained with fewer co-products
- This means that product separation is simpler
113
Why do we classify living things?
- For our convenience
- To make the study of living things more manageable
- To make it easier to identify organisms
- To help us see the relationships between species
114
What is the current system of classification?
There are 8 taxa:
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
115
What is taxonomy?
The study of the principles behind classification
116
What is classification?
Sorting living things into groups
117
What are the 3 domains for classification?
- Bacteria (eubacteria)
- Archaea (archaebacteria)
- Eukaryotae
118
What is the binomial system?
A system that uses 2 names to identify each species:
| - The genus name and the species name
