Topic 8 - Fuels and Earth Science Flashcards
Hydocarbons are
Compounds that only contain carbon and hydrogen
Crude oil is
A complex mixture of hydrocarbons.
The hydrocarbons have their carbons arranged in chains or rings
Important source of substances called a feedstock for petrochemical industry)
A finite resource
Crude oil is seperated by
Fractional distillation
Fractional distillation is
When the oil is heated to a gas then enter the fractionating column where there is a temp gradient.
It is hot at the bottom and cooler at the top.
The longer hydrocarbons have higher boiling points, so condensate at the bottom.
Creates 6 different fractions
The 6 fractions in fractional distillation(top to bottom)
Gases
Petrol
Kerosene
Diesel oil
Fuel oil
Bitumen
Use of gases fraction
Used in domestic heating and cooking
Petrol fraction use
Fuel for cars
Kerosene fraction use
Fuel in aircraft
Diesel oil fraction use
Fuel in some cars, larger vehicles and trains
Fuel oil fraction use
Fuel for large ships and soem power stations
Bitumen fraction use
Used to surface roads and roofs
The lower the fraction in fractional distillation,
The number of hydrogen and carbon atoms in molecules increase
Boiling point increases
Ease of ignition decreases
Viscocity increases
The hydrocarbons in crude oil are mainly
part of the alkane homologous series
A homologous series is
A family of molecules which have the same general formula and share similar chemical properties.
They differ from neighbouring compounds by a CH2
Gradual variation in physical properties
two homologous series’ of hydrocarbons
Alkanes and alkenes
Hydrocarbons are good fuels because
The combustion reactions give out lots of energy. Very exothermic.
When hydrocarbons are burned in plenty of oxygen
Complete combustion occurs, and the only products formed are carbon dioxide and water.
Release lots of energy
When hydrocarbons are burned in insufficient oxygen
Incomplete combustion occurs.
This produces carbon dioxide and water, but also carbon and carbon monoxide(CO)
Why is carbon monoxide bad
It is toxic as it combines with red blood cells and stops blood carryign oxygen.
This can lead to death
Why is carbon bad
Tiny particles of it are relased into the atomsphere, and when they fall they form balck dust called soot.
Reduces air quality and makes builidings look dirty
Incomplete combustion occurs in
Some appliances that use carbon compounds as fuels
Sulfur dioxide can be produced by fossil fuels if
They contain sulfur impurities
Sulfur dioxide is bad because
It mixes with the clouds and forms dilute sulfuric acid. This falls as aicd rain
Acid rain is bad because
It causes lakes to become acidic, and many plants and animals die
Kills trees, damages limestone buildings and stone statues, and causes metal corrosion
Nitrogen oxides are produced by
Reactions between nitrogen and oxygen in the air caused by the energy released in combustion(eg by car engines)
Nitrogen oxides are bad because
They are harmful ppolutants that can contribute to acid rain, and can cause a photochemical smog, which leads to breathing difficulties
Advanatges of using hydrogen to fuel cars
Very clean fuel
Only waste product is water
Renewable resource as it is obtained by the electrolysis of water
Disadvantages of using hydrogen to fuel cars
Expensive engine
Expensive to obtain pure hydrogen
Hydrogen is hard to store
Non-renewable fossils fuels from crude oil
Petrol
Kerosene
Diesel oil
Non-renewable fossil fuel found in natural gas
Methane
Cracking is
The splitting up of long, saturated hydrocarbons(alkanes) into smaller hydrocarbons. Some of the smaller ones are unsaturated(alkenes)
Cracking is done by
Heating up a larger hydrocarbon, and breaking the strong covalent bonds.
Cracking process
Vaporised hydrocarbons are passed over powdered catalysts at about 400C-700C. Pressure of 70atm.
Aluminium oxide is the catalyst used, and the large lakanes split apart in the conditions.
Cracking is necessary because
Because the demand for petrol and diesel is much higher than fuel oil and bitumen, so they are broken down to make more of the in-demand alkanes. It also can produce and alkene used to make polymers.
The eartghs early atomsphere was formed by
Volcanoes releasing gases(carbon dioxide, steam, methane and ammonia).
Early atmosphere contained
Little or no oxygen
Large amount of CO2
Water vapour
Small amounts of other gases(ammonia, methane)
Oceans formed by
Water vapour condensed into large masses of water
The amount of CO2 in the atomsphere first decreased by
CO2 dissolving into the oceans
How was nitrogen gas put in the atmosphere
Ammonia reacting with oxygen, released by denitrifying bacteria.
N2 isnt reactive so increased in amount
How did oxygen get into the ealry atmosphere
Green plants evolved and photosynthesised. Slowly removed CO2 and produced o2
Oxygen in the ealry atmosphere allowed`
Complex organisms to evolve
Created the ozone layer
Chemical test for oxygen
If the gas relights a glowing splint it is oxygen
The greenhouse effect process
EM radiation from sun gets filtered through the atmosphere and some gets in.
Short wavelengths are absorbed which warms the planet
The earth radiates some heat radiation that has been absorbed from longer wavelength IR radiation
Some of this is absorbed by greenhosue gases
The gases radiate some of it back to earth
The absorbtion and re-emission of this IR is what keep the earth warm
Greenhouse gases are
The gases in the atmosphere that can absorb and reflect heat radiation. Carbon dioxide, steam, methane etc
Human activity is causing
CO2 concentration to increase
Temperature change is correlated to
the increase in CO2 and methane concentration in recent decades
There are uncertainties in historical data because
The measurements were less accurate and sometimes non-existent.
Some of it is predicted using analysis of fossils and gas bubbles
Composition of todays atmosphere
Nitrogen mainly
20% oxygen
Less than 0.1% of CO2
Tiny amounts of methane
CO2 concentration has increased due to
Burning of fossils fuels to meet higher energy demands. deforestation to house people and grow food.
Methane concentration increase due to
Higher amount of livestock farmed. They produce methane in digestive process.
CO2 and methane increase is bad because
It leads to global warming due to too much greenhouse effect
