Energy Option

Question 1

energy from the sun

Answer 1

comes from uncontrolled nuclear fusion reactions

Question 2

photosynthesis

Answer 2

• reaction of carbon dioxide and water to form carbohydrates in the presence of chlorophyll
• endothermic

Question 3

give details of photosynthesis

Answer 3

• green pigment chlorophyll contains an extended system of alternating single and multiple bonds (conjugation)
• substances like chlorophyll contain extended conjugation and are able to absorb visible light by exciting an electron within this conjugated system
• energy which is absorbed by chlorophyll when it interacts with light is able to drive photosynthesis

Question 4

how can the energy stored in biomass by released?

Answer 4

• direct combustion of plant material
• biogas: anaerobic decay of organic matter by bacteria produces a mixture of methane and carbon dioxide
• fermentation to produce ethanol: carbohydrates can be fermented by enzymes in yeast

Question 5

biofuel advantages

Answer 5

• renewable
• readily available
• relatively non-polluting
• reduces amount of waste in landfill sites

Question 6

biofuel disadvantages

Answer 6

• widely dispersed
• take up land where crops can be grown
• remove nutrients from soil

Question 7

vegetable oils

Answer 7

• derived from glycerol and unsaturated fatty acids
• contain considerable amount of energy
• cannot be used in internal combustion because they are too viscous (because they have a high molar mass)

Question 8

transesterification

Answer 8

• vegetable oils converted into usable fuel
• ester can react with an alcohol to be converted into a different ester in the presence of strong acid or base

Question 9

greenhouse effect

Answer 9

warming of the Earth caused by infrared radiation emitted by the Earth’s surface which is absorbed by various gases in the Earth’s atmosphere and then partly re-radiated towards the surface

Question 10

greenhouse gases

Answer 10

• water vapor
• carbon dioxide
• methane
• nitrous oxide

Question 11

Why do greenhouse gases absorb infrared radiation?

Answer 11

• resonance
• must be a change in dipole moment as bonds in the molecule stretch and bend

Question 12

enhanced greenhouse effect

Answer 12

greenhouse effect caused by human activities

Question 13

energy flow diagram of greenhouse effect

Answer 13

Question 15

what are two consequences of global warming?

Answer 15

• changes in agriculture and biodistribution as climate changes
• rising sea-levels due to thermal expansion and melting polar ice caps and glaciers

Question 16

what influences the contribution a greenhouse gas makes to global warming?

Answer 16

• concentration in atmosphere
• ability to absorb infrared radiation

Question 17

ways to limit human-made emissions of carbon dioxide

Answer 17

• reducing dependency on fossil fuels
• capturing gas chemically using sodium hydroxide or calcium oxide
• stored in certain types of silicon-based rocks

Question 18

why are coral reefs being destroyed?

Answer 18

• increase in concentration carbon dioxide in atmosphere leads to increase concentration of carbon dioxide dissolved in ocean
• ocean more acidic

Question 19

particulate

Answer 19

• e.g. soot and volcanic dust
• cool the earth by scattering the shortwave radiation from the sun and reflecting it back into space

Question 20

energy

Answer 20

ability to do work

Question 21

first law of thermodynamics

Answer 21

energy within a closed system can neither be created nor destroyed

Question 22

order for the main energy sources in terms of producing energy

Answer 22

crude oil > coal > natural gas > hydroelectric > nuclear fission > wind > biofuels > solar > geothermal

Question 23

why is the production of energy not 100% efficient?

Answer 23

heat loss

1. to surroundings
2. by power lines

Question 24

energy density equation

Answer 24

energy released from fuel / volume of fuel consumed

Question 25

specific energy equation

Answer 25

energy released from fuel / mass of fuel consumed

Question 26

efficiency of an energy transfer

Answer 26

useful output energy / total input energy \*100

Question 27

why must sulfur be removed from crude oil before it is refined?

Answer 27

can poison catalysts by blocking their active sites

Question 28

fractional distillation

Answer 28

separating crude oil into different boiling fraction

Question 29

fraction from distillation

Answer 29

1. refinery gas: used as fuel on site, gaseous cooking fuel, feedstock for chemicals 2. gasoline and naphtha: cars, feedstock for organic chemicals 3. kerosene: fuel for jet engines, domestic heating, cracked to provide petrol 4. gas oil: diesel engines and industrial heating, cracked to provide petrol 5. residue: fuel for large furnaces, vacuum distilled to make lubricants, bitumen used to surface roads

Question 30

cracking

Answer 30

* process conducted at high temperatures whereby large hydrocarbons are broken down into smaller more useful molecules * usually alkanes and alkenes

Question 31

isomerization

Answer 31

more useful branched alkanes can be obtained from straight-chain hydrocarbons by mixing them with hydrogen and heating them at 770K over a platinum catalyst at high pressure

Question 32

what are other reforming processes?

Answer 32

* cyclization to make ring molecules * aromatization to make benzene

Question 33

carbon footprint

Answer 33

* total amount of greenhouse gases produced during human activities * expressed in equivalent tons of carbon dioxide

Question 34

where does the majority of the carbon footprint come from?

Answer 34

indirectly from fuel used to produce and transport goods compared with the emissions which come directly from using gasoline in their own car

Question 35

how can consumers offset their carbon footprint?

Answer 35

* planting trees * reduce the use of fossil fuels and materials in general * reuse materials and recycle

Question 36

knocking

Answer 36

under the conditions of high temperature and pressure the reaction may start before the spark and the engine will be less efficient

Question 37

octane number

Answer 37

more branched the alkane the higher the octane number

Question 38

coal gasification

Answer 38

* crushed coal is mixed with superheated steam * synthesis gas produced: mixture of carbon monoxide and hydrogen

Question 39

how to produce SNG?

Answer 39

* reacting coal gas with more hydrogen in the presence of a heated catalyst * heating crushed coal in steam at 700C using potassium hydroxide as a catalyst

Question 40

SNG

Answer 40

* cleaner gas as it removes pollution due to sulfur dioxide * easier to transport * less efficient

Question 41

Fischer-Tropsch process

Answer 41

* synthesis gas is reacted with more steam to increase the proportional of hydrogen in the mixture * hydrogen and carbon monoxide are then passed into a fluidized bed reactor containing iron or cobalt catalysts to produce a mixture of hydrocarbons that can be separated by fractional distillation

Question 42

what is the primary component of natural gas?

Answer 42

methane

Question 43

coal advatnages

Answer 43

* present in large quantities and distributed throughout the world * can be converted into synthetic liquid fuels and gases * feedstock for organic chemicals * has the potential to yield vast quantities of energy compared with renewable sources * safer than nuclear power * longer lifespan compared with oil or gas

Question 44

coal disadvantages

Answer 44

* contributes to acid rain and global warming * not so readily transported * coal waste lead to ground acidity and visual and chemical pollution * mining is dangerous * dirty (produces dust, smoke and particulates)

Question 45

oil advantages

Answer 45

* easily transported in pipelines * convenient fuel for use in cars * feedstock for organic chemicals

Question 46

oil disadvantages

Answer 46

* contributes to acid rain and global warming * limited lifespan and uneven distribution worldwide * risk of pollution associated with transportation by tankers

Question 47

natural gas advantages

Answer 47

* clean fuel * easily transported in pipelines and pressurised containers * does not contribute to acid rain * releases a higher quantity of energy per kg than coal or oil

Question 48

natural gas disadvantages

Answer 48

* contributes to global warming * limited lifespan and uneven distribution worldwide * greater risk of explosions due to leaks

Question 49

chemical reaction vs. nuclear reaction

Answer 49

* chemical reaction: valence shell electrons rearranged * nuclear reaction: nucleus itself rearranges

Question 50

nuclear fusion

Answer 50

small atoms combine to form heavier nuclei

Question 51

nuclear fission

Answer 51

splitting of heavy nuclei to form two or more lighter nuclei

Question 52

nuclear safety concerns

Answer 52

1. meltdown: occurs when a nuclear reactor becomes out of control and essentially becomes a nuclear bomb 2. escape of radioactive material: occur as the fuel is being transported or while it is being used 3. high-level nuclear waste: must be stored for a very long time 4. low-level nuclear waste: gloves, etc. that have been used in areas where radioactive materials are handled

Question 53

half-life

Answer 53

time after which the number of radioactive nuclei is reduced by a factor of 2

Question 54

how can supplies of methane be increased?

Answer 54

* cracking larger hydrocarbons * coal gasification