Biogeochem - hydrocarbons Flashcards
At what temperature does oil become gas?
when its heated above 180ºC
what makes oil more viscous
the more carbon atoms, the more viscous the liquid is
Can oil be found on land?
Oil can be found on land in areas that used to be underwater
Characteristics of hydrocarbons
- organic
- hydrogen and carbon
- carbon-carbon bonds
- carbon-hydrogen bonds
- water insoluble
- resistant to degradation
list the aliphatic hydrocarbons
alkanes, cycloalkanes, alkenes, alkynes
Why alkanes saturated?
they have a single bond
why are molecules with double or triple bonds more reactive than single bonds?
the electrons in multiple bonds are more easily accessible and can be donated to other atoms or molecules more readily
whats the prefix order for al-kanes, kynes and kenes
meth
eth
prop
but
pent
hex ….
what type of bond do alkenes have?
double carbon bond
c=c bond
what type of bond do alkynes have
triple carbon bond
Environmental impacts of hydrocarbon spillage
impacts wildlife by attaching to fur or wings
covers rocky shores, sandy beahces, shingle beaches, mud shores, saltmarshes etc
socia-economic impacts
effects tourism and reduces income
expensive to use dispersants which breaks up the oil particle
costs of unexpected consequences (eg burning it)
Dispersal of spilled hydrocarbon stages
Spreading
Evaporation
Dispersion
Dissolution
Emulsification
Oxidation
Sedimentation
Biodegradation
what factors determine the rate of spread of oil
- oil viscosity (chain length)
- wind
- currents
- warmer temperatures
what is the process of hydrocarbon spreading?
- 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
what is the process of oil spill evaporation?
- 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
what is the process of oil spill dispersion
- 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
what types of sheens are there?
rainbow
metallic
grey
dark
what is the dissolution process in an oil spill
- 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
what is the process of emulsification?
- 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
what is the process of oxidation in an oil spill
- 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
what is the process of sedimentation in oil spills
- sediment (eg clay, silt) mixes with the oil
- the oil attaches to the sediment particles and sink to the seafloor
- process can take years
what is the process of biodegradation?
- 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.
