topic 8 - fuels and earth sciences

state what hydrocarbons are

• compounds that contain

• ONLY

• carbon and hydrogen atoms

explain what crude oil is

• a complex mixture of hydrocarbons

• containing molecules

• in which carbon atoms are in chains or rings

• an important source of useful substances

• a finite resource

describe and explain how crude oil is separated into more useful mixtures by fractional distillation

1. fractional distillation is carried out in a fractionating column which is very hot at the bottom and very cool at the top

2. crude oil enters the fractionating column and is heated, so the crude oil vapour rises

3. vapours of hydrocarbons with very high boiling points will cool and condense and be collected at the bottom of the column

4. vapours of hydrocarbons with very low boiling points will cool and condense and be collected at the top of the column

5. different fractions condense at different heights based on their boiling point

6. fractions containing smaller hydrocarbons will be collected as gases in higher sections of the column

7. fractions containing larger hydrocarbons will be collected in lower sections of the column

state the uses of natural gases

• domestic heating

• cooking

state the use of petrol

fuel for cars

state the use of kerosene

fuel for aircrafts

state the uses of diesel oil

• fuel for some cards

• fuel for trains

state the uses of fuel oil

• fuel for large ships

• fuel for power stations

state the uses of bitumen

• used to surface roads

• used to surface roofs

explain how hydrocarbons in different fractions within crude oil differ from each other by the number of carbon and hydrogen atoms they contain

• fractions with longer hydrocarbons will have more hydrogen and carbon atoms

• fractions with shorter hydrocarbons will have less hydrogen and carbons

• as the length of the chain relies on the amount of carbon atoms in the molecules

explain how hydrocarbons in different fractions within crude oil differ from each other by boiling points

• fractions with longer hydrocarbons will have higher boiling points

• fractions with shorter hydrocarbons will have lower boiling points

• as it takes more energy to overcome more covalent bonds between carbon and hydrogen atoms

explain how hydrocarbons in different fractions within crude oil differ from each other by ease of ignition

• fractions with longer hydrocarbons will be harder to ignite

• fractions with shorter hydrocarbons will be easier to ignite

• as it takes more energy to overcome more covalent bonds between carbon and hydrogen atoms

explain how hydrocarbons in different fractions within crude oil differ from each other by viscosity

• fractions with longer hydrocarbons will be more viscous

• fractions with shorter hydrocarbons will be less viscous

• as the intermolecular forces of attraction in longer hydrocarbon chains are stronger

• and there is a higher chance of longer chains entangling

state what the different hydrocarbon fractions within crude oil have in common

they are mostly members of the alkane homologous series

explain what a homologous series is

• a series of compounds

• which have the same general formula

• differ by CH₂ in molecular formulae from neighbouring compounds

• show a gradual variation in physical properties

• and have similar chemical properties

describe what the complete combustion of a hydrocarbon is

• an exothermic reaction

• where carbon dioxide and water are produced

• and energy is given out

state what the incomplete combustion of hydrocarbons produces

• carbon/soot

• carbon monoxide

explain why the incomplete combustion of hydrocarbons produces carbon and carbon monoxide

• an incomplete combustion occurs due to a lack of enough oxygen

• carbon and carbon monoxide are produced as there is not enough oxygen to produce carbon dioxide and water

explain how carbon monoxide behaves as a toxic gas

• carbon monoxide causes loss of consciousness and suffocation

• as once breathed in, it binds to haemoglobin in the blood

• meaning oxygen cannot bind to the haemoglobin

• restricting the amount of oxygen carried around the body to organs

• causing suffocation

explain the problems of incomplete combustion in appliances that use carbon compounds as fuel

• when incomplete combustion occurs, carbon and carbon monoxide are created

• these can be used as fuel by the appliance

• and cause an electrical fire

explain how impurities in some hydrocarbon fuels results in the production of sulfur dioxide

• hydrocarbon fuels are often contaminated with small amounts of sulfur impurities

• when these fuels are combusted, the sulfur in the fuels gets oxidised

• which forms sulfur dioxide

explain some problems associated with acid rain caused when sulfur dioxide dissolves in rain water

• acid rain can cause corrosion to metal structures, buildings and statues made of carbonate rocks

• acid rain can damage aquatic organisms

• acid rain can pollute crops and water supplies

• acid rain can irritate lungs, throats and eyes

explain why, when fuels are burned in engines, oxygen and nitrogen can react at high temperatures to produce nitrogen oxides

• nitrogen oxides are produced when nitrogen and oxygen react at high temperature and pressures inside internal combustion engines

• nitrogen oxides are pollutants

state the advantages of using hydrogen instead of petrol as a fuel in cars

• it releases more energy per kilogram than any other fuel

• it does not pollute as it only produces water during combustion

state the disadvantages of using hydrogen instead of petrol as a fuel in cars

• its expensive to produce and requires energy for the production process

• its difficult and dangerous to store and move around

• the production of hydrogen releases carbon dioxide

state what type of fuel petrol, kerosene and diesel oil are

• non-renewable fossil fuels

• obtained from crude oils

state what type of fuel methane is

• non-renewable fossil fuel

• obtained from natural gases

state what cracking is

• the breaking down of larger, saturated hydrocarbons (alkanes)

• into smaller, more useful saturated hydrocarbons

• and some unsaturated hydrocarbons (alkenes)

explain why cracking is necessary

• some shorter chain hydrocarbons are in higher demand

• than long chain hydrocarbons

• cracking allows the long chain hydrocarbons to be broken down into shorter chain hydrocarbons

• therefore not wasting long chain hydrocarbons

• and increasing the supply of shorter chain hydrocarbons

• which are more reactive, less flammable and less viscous

state what is produced by volcanic activity in earth’s early atmosphere

gases

state what earth’s early atmosphere was thought to contain

• little or no oxygen

• a large amount of carbon dioxide

• water vapour

• small amounts of other gases

explain how condensation of water vapour formed oceans

• as volcanic activity decreased, global temperature decreased

• this cooling of temperature caused the condensation of water vapour into liquid water

• this liquid water formed the oceans

explain how the amount of carbon dioxide in the atmosphere was decreased when carbon dioxide dissolved as the oceans formed

• carbon dioxide is water soluble

• when water vapour in earth’s early atmosphere condensed, carbon dioxide dissolved in the oceans

• carbonates were precipitated during this process, later forming sediments on the seabed

explain how the growth of primitive plants gradually increases the amount of oxygen in earth’s early atmosphere

• plants use photosynthesis to create energy in glucose form

• carbon dioxide is a reactant in photosynthesis

• oxygen is a product of photosynthesis

• as plants continued to grow, the amount of oxygen in the atmosphere increased

• and the amount of carbon dioxide in the atmosphere decreased

describe the chemical test for oxygen

• place a glowing splint in a test tube containing the unknown gas

• if the splint relights, oxygen is present

explain what the greenhouse effect is

• when carbon dioxide, methane and water vapour in earth’s atmosphere

• absorb heat radiated from the earth

• and subsequently release energy which keeps earth warm

evaluate the evidence for human activity causing climate change, considering the correlation between the change in atmospheric carbon dioxide concentration, the consumption of fossil fuels and temperature change

• fossil fuels are the most used energy source globally

• when fossil fuels are combusted, they produce the greenhouse gases: carbon dioxide, methane and nitrous oxide

• these gases enhance the greenhouse effect, allowing for a global temperature increase

• and climate change

evaluate the evidence for human activity causing climate change, considering the locations where the greenhouse gas measurements are taken and historical accuracy

• historical data is much less accurate due to the lack of accurate instrumentation and methods

• fewer locations would have been measured due to lack of satellites and transport

state the composition of earth’s modern atmosphere

• 78% nitrogen

• 21% oxygen

• 1% argon

• ~1% carbon dioxide

• ~1% neon

• ~1% methane

explain the potential effects of increased levels of carbon dioxide and methane on the climate

• carbon dioxide and methane are greenhouse gases

• so once they’re in the atmosphere, they enhance the greenhouse effect

• this increases the heating effect on the earth

• increasing global temperature

• and increasing the chances and effects of climate change occurring

state the main way carbon dioxide is released into the atmosphere

• the combustion of fossil fuels

• as carbon dioxide is a product of the complete combustion of hydrocarbons within the fossil fuels

state the main way methane is released into the atmosphere

• livestock farming

• as during the digestive processes, farm animals produce methane

• which is then released into the environment

explain how the amount of carbon dioxide released into the atmosphere can be decreased

• changing from using fossil fuels as an energy source to renewable energy sources such as solar or wind

• as this will decrease the demand for fossil fuels

• decreasing the amount of fossil fuels being combusted

• decreasing the carbon dioxide being released into the atmosphere

explain how the effects of carbon dioxide in the atmosphere can be mitigated

• planting more plants and trees

• as they will use up carbon dioxide during the photosynthesis reaction

• and produce oxygen as a product

explain how the amount of methane released into the atmosphere can be decreased

• people adopting a vegetarian or vegan diet

• as this will decrease the demand for livestock

• therefore decreasing the amount of livestock being farmed

• decreasing the amount of methane being produced