Biogeochem - hydrocarbons

Question 1

At what temperature does oil become gas?

Answer 1

when its heated above 180ºC

Question 2

what makes oil more viscous

Answer 2

the more carbon atoms, the more viscous the liquid is

Question 3

Can oil be found on land?

Answer 3

Oil can be found on land in areas that used to be underwater

Question 4

Characteristics of hydrocarbons

Answer 4

• organic
• hydrogen and carbon
• carbon-carbon bonds
• carbon-hydrogen bonds
• water insoluble
• resistant to degradation

Question 5

list the aliphatic hydrocarbons

Answer 5

alkanes, cycloalkanes, alkenes, alkynes

Question 6

Why alkanes saturated?

Answer 6

they have a single bond

Question 7

why are molecules with double or triple bonds more reactive than single bonds?

Answer 7

the electrons in multiple bonds are more easily accessible and can be donated to other atoms or molecules more readily

Question 8

whats the prefix order for al-kanes, kynes and kenes

Answer 8

meth
eth
prop
but
pent
hex ….

Question 9

what type of bond do alkenes have?

Answer 9

double carbon bond

c=c bond

Question 10

what type of bond do alkynes have

Answer 10

triple carbon bond

Question 11

Environmental impacts of hydrocarbon spillage

Answer 11

impacts wildlife by attaching to fur or wings

covers rocky shores, sandy beahces, shingle beaches, mud shores, saltmarshes etc

Question 12

socia-economic impacts

Answer 12

effects tourism and reduces income
expensive to use dispersants which breaks up the oil particle
costs of unexpected consequences (eg burning it)

Question 13

Dispersal of spilled hydrocarbon stages

Answer 13

Spreading
Evaporation
Dispersion
Dissolution
Emulsification
Oxidation
Sedimentation
Biodegradation

Question 14

what factors determine the rate of spread of oil

Answer 14

• oil viscosity (chain length)
• wind
• currents
• warmer temperatures

Question 15

what is the process of hydrocarbon spreading?

Answer 15

• spilt oil floats to the surface and spreads
• the rate of spread is determined by oil viscosity (with lighter oils being spread further), currents and wind
• windrows can form which are narrow bands of oil parallel to the wind direction
• this process can take hours to a week
• 1 ton of spilt oil = 10,000m2 area of oil spilt

Question 16

what is the process of oil spill evaporation?

Answer 16

• sun heats the oil
• lighter elements get transformed to vapour from water and evaporate (20-60% of crude oil evaporates)
• this leaves behind the more viscous, thicker oil that is more resistant to naturally dissolving
• process can take a week

Question 17

what is the process of oil spill dispersion

Answer 17

• weathering can break down the oil into smaller droplet particles
• these sink and mix in the upper water column and rise again
• they then collect and form a sheen
• process can take about a month

Question 18

what types of sheens are there?

Answer 18

rainbow
metallic
grey
dark

Question 19

what is the dissolution process in an oil spill

Answer 19

• with weathering, some particles dissolve into the seawater
• the components that are more likely to evaporate are the components which dissolve into the seawater
• this can take about a month

Question 20

what is the process of emulsification?

Answer 20

• waves churn up the oil particles, encapsulating them in water molecules from surrounding water
• this forms an oil-water emulsion which becomes more resistant to weathering
• this process can enhance the spread as it increases the volume of hydrocarbons
• 1000 tonnes spilt = 2800 tonnes of emulsion

Question 21

what is the process of oxidation in an oil spill

Answer 21

• Redox reactions occur, resulting in the hydrocarbons getting oxidised, producing tar and tarballs
• tarballs are balls of oxidised oil with a solid outer crust and softer or liquid core
• tar balls last a long time after the spill has been cleared up
• tar and tarballs slow down the degradation process

Question 22

what is the process of sedimentation in oil spills

Answer 22

• sediment (eg clay, silt) mixes with the oil
• the oil attaches to the sediment particles and sink to the seafloor
• process can take years

Question 23

what is the process of biodegradation?

Answer 23

• marine microorganisms (eg algae, bacteria, fungi) feed on the hydrocarbons in the oil for energy
• they can only remove small parts of the oil or removed the reminants off affected shorelines
• this process is difficult to achieve early on because, due to reasoning behind oil formation, it is reluctant to degradation.