Fuels and Earth Science Flashcards
What is a hydrocarbon?
A compound that contains hydrogen and carbon only
What is a crude oil?
- Complex mix of hydrocarbons
- Contains molecules where carbon are in chains or rings
- Important source of useful substances, e.g. fuels and feedstock
- Finite resource
How is crude oil separated into useful mixtures?
- Fractional distillation
- Crude oil is heated in the fractionating column and the oil becomes a gas.
- The gas rises through the column which gets cooler further up and condenses at a variety of different temperatures based on the hydrocarbon’s boiling point.
Name each fraction and their uses
● Gases: domestic heating and cooking
● Petrol: fuel for cars
● Kerosene: fuel for aircraft
● Diesel oil: fuel for some cars and trains
● Fuel oil: fuel for large ships and in some power stations
● Bitumen: surface roads and roofs
How does each fraction differ in properties and why?
- Number of atoms in molecule: increase downwards
- Boiling point: increases downwards
- Ease of ignition: increases upwards
- Viscosity: increases downwards
Physical properties dependent on intermolecular forces that hold chains together, more atoms stronger the force
- Boiling point: more forces of attraction to break in large molecules, high boiling point
- Ease of ignition: Long hydrocarbons have a high boiling point and are hard to ignite
- Viscosity: Stronger forces of attraction between hydrocarbons, harder it is for the liquid to flow
What is a homologous series?
A series of compounds which:
- have the same general formula
- similar chemical properties
- have gradual change in physical properties
What happens in complete combustion and what kind of reaction is it?
- When carbon dioxide and water is produced
- Exothermic reaction
Why does incomplete combustion happen and what gets produced?
Incomplete combustion occurs when there is not enough oxygen around
- produces carbon monoxide and carbon in the form of soot
Why is carbon monoxide toxic?
- Combines with haemoglobin so the red blood cells can’t do the proper job of carrying oxygen around the body
- Can lead to fainting, coma and possibly death.
What are the issues with incomplete combustion?
- Produces soot which makes buildings look dirty, reducines air quality and can cause or worsen breathing problems
- Carbon monoxide is a toxic gas which can kill
How is sulfur dioxide produced?
Most fuels contain some sulfur, and when reacting with oxygen, it produces sulphur dioxide.
What issues arise when sulphur dioxide combines with rainwater?
- Causes lakes to become acidic
- Kills trees
- Damages limestone buildings
- Damages stone statues
- Makes metal corrode
How are oxides of nitrogen produced?
- When fuels are burnt, nitrogen in the air reacts with oxygen at high temperatures to produce nitrogen oxides.
What are the issues with nitrogen oxides?
- Contribute to acid rain
- Cause photochemical smog
Advantages and disadvantages of using hydrogen as fuel.
Pros:
- Clean fuel, only produces water in a fuel cell
- Hydrogen obtained from water, so won’t run out. Can even be produced by the water made by the fuel cell
Cons:
- Need expensive engine
- Hydrogen gas needs to be manufactured, uses energy from fossil fuels
- Hard to store
What is methane?
non-renewable fossil fuel found in natural gas
what is cracking and what conditions are required for it?
- Breaking of large, saturated alkanes into smaller more useful unsaturated alkenes and alkanes.
- Requires heat, moderate pressure and a catalyst.
Why is cracking required?
- To help supply and demand, can produce smaller hydrocarbons which are higher in demand.
How was earth’s early atmosphere formed?
intense volcanic activity that released gas that formed the early atmosphere
What did earth’s early atmosphere contain?
- Little or no oxygen
- A lot of CO2
- Water vapour
- Small amounts of other gases
How were oceans formed?
- Water vapour condensed to form the ocean.
How did the amount of carbon dioxide in the atmosphere decrease?
- CO2 dissolved into the water
How did the volume of oxygen in the atmosphere increase?
- Plants evolved and as they photosynthesised, they removed CO2 and produced O2.
- This led to the amount of O2 in the air building up.
What is the chemical test for oxygen?
Put a glowing splint in oxygen and it will relight.
How do greenhouse gases work?
- The sun releases short wavelength EM radiation, which passes through the atmosphere.
- The radiation reaches the Earth’s surface and is absorbed and then re-emitted as a IR radiation
- This gets absorbed by greenhouse gases such as CO2, methane and water vapour
- The gases then re-radiate it in all directions, including back to the earth.
- IR radiation is thermal radiation, so this warms up the earth.
Why can historical data on temperature less accurate?
- Taken over a small range of places
- Inaccurate equipment
What is the composition of todays atmosphere
78% nitrogen
21% oxygen
1% argon
less than 1% other gases
Effects of livestock farming on the atmosphere?
- Methane produced by digestive processes of some livestock, so the more livestock farmed, more methane produced.
- Methane is a greenhouse gas.
How can the effects of climate change be mitigated
- reduce fossil fuels usage
- encourage public and industry to become more energy efficient
