topic 8

• How is crude oil formed?

  Over millions of years from the fossilised remains of plankton
• What is crude oil?

  A mixture of hydrocarbons forming a non-renewable, finite fuel.
• Why is crude oil separated into fractions?

  Because each fractions has a different use, but when together, the crude oil is not very useful
• How is crude oil separated?

  fractional distillation
• Describe fractional distillation of crude oil

  Crude oil is heated until it boils

  Some molecules will still be liquid and will drop to the bottom

  All others - gases - rise

  Rise -> lose energy, further from the heat source -> temperature decreases

  When a compound reaches its condensing point it will condense into a liquid and be collected

  The tube is hottest at the bottom, and coolest at the top, meaning long chains with the highest boiling/ condensing points condense first, and exit the tube at the bottom
• Do longer or shorter hydrocarbons have higher bpts/ mpts , and why?

  Longer - they have more bonds, so require more energy to break.
• List the hydrocarbons in crude oil, from longest chain to shortest chain

  Bitumen, Fuel Oil, Diesel Oil, Kerosene (paraffin), Petrol and Gases
• What are the uses of Bitumen?

  Surfacing roads and roofs
• What are the uses of fuel oil?

  Fuel for large ships and some power stations
• What are the uses of diesel oil?

  Fuel for cars, lorries and buses, as well as larger vehicles like trains
• What are the uses of Kerosene?

  Aircraft fuel
• What are the uses of petrol?

  Fuel for cars
• What are the uses for the gases (shortest hydrocarbons) produced from refining crude oil?

  Domestic heating and cooking
• Why are hydrocarbons used as fuel?

  Their reactions with oxygen (combustion reactions) are exothermic and give out lots of energy
• What is the general formula for when a hydrocarbon combusts?

  Hydrocarbon + oxygen -> carbon dioxide + water
• What is a homologous series?

  A group of molecudes with the same functional group, general formula, and similar chemical properties
• What are two examples of homologous series?

  Alkenes and Alkanes
• How does the boiling points of longer and shorter hydrocarbons differ?

  Intermolecular forces are stronger in longer molecules, so longer hydrocarbons require more energy to break, and therefore have higher melting and boiling points.
• How does the ease of ignition of longer and shorter hydrocarbons differ?

  Shorter hydrocarbons are easier to ignite, as with lower boiling points, they tend to be gases at room temperature. They mix with oxygen in the air to produce a gas mixture which would light if it came into contact with a spark.
• What is viscosity?


  How easily a substance flows - higher viscosity = flows less easily
• How does the viscosity of longer and shorter hydrocarbons differ?

  Longer hydrocarbons have a higher viscosity, they are thik like treacle. Shorter ones have a lower viscosity becasue they are much runnier.
• What is cracking?


  Splitting up long chain hydrocarbons into shorter chains.

  It is a form of thermal decomposition, which is when one substance breaks into two or more new ones after being heated.
• Why is cracking necessary?

  There is a higher demand of shorter hydrocarbons, and long ones are produced in excess. Cracking doesn't waste the longer hydrocarbons, and keeps up with the demand for shorter chains.
• How can cracking be done in a lab?

  Heat the alkane until it's vaporised

  Pass it through a horizontal tube containing the aluminium oxide catalyst.

  A mixture of shorter chain alkane and alkenes will be acheived.
• What does incomplete combustion produce?

  Carbon monoxide and water, as well as soot
• Why is sulphur dioxide bad for the environment?

  It reacts with water vapour and oxygen in the air to form sulphuric acid. Sulphuric acid contributes towards acid rain, which damages habitats and kills fish and other animals.
• Why is carbon monoxide harmful?

  It's poisonous, bonds to haemoglobin in red blood cell and forms carboxyhaemoglobin, blood can't carry around as much oxygen, meaning it can casue fainting, a coma or even death
• Why is soot bad for health and the environment?

  They make buildings look dirty, reduce air quality, and can worsen or cause respiratory illnesses
• Why are nitrogen oxides bad?


  NO gases react to form photochemical smog, which is a type of air pollution that can cause breathing difficulties, headaches and tiredness.
• What are the advantages of using hydrogen as a fuel?

  - only waste product is water

  - hydrogen is obtained from electrolysis of water which is a renewable resource, so won't run out
• What are the disadvantages of using hydrogen as a fuel?

  - A special, expensive engine is needed

  - Hydrogen gas needs to be manufactured, which is expensive and often sues energy from another source, often from burning fossil fuels, which does produce pollutants

  - hydrogen is explosive and hard to store and not widely available
• Describe phase one of the earth's atmosphere - volcanoes giving out steam and...

  - Surface is molten

  - volcanoes erupted, giving out CO2, methane, ammonia and water vapour

  - atmosphere was mostly CO2

  - water vapour later condensed to form oceans
• Describe phase 2 of the earth's atmosphere - green plants evolved and produced...

  - lots of the CO2 dissolved into the oceans

  - nitrgoen gas was released into the atmosphere from denitrifying bacteria, and from ammonia reacting with O2

  - green plants removed CO2 and added O2 to the atmosphere

  - CO2 got locked up in fossils and sedimentary rocks
• Describe phase 3 of the earth's atmosphere - the ozone layer allowed...


  - build up of O2 killed off orgaisms which couldn't tolerate it, and allowed evolution of more complex organisms

  - oxygen created the ozone layer (O3) which blocked harmful rays of the sun and allowed even more complex organisms to evolve

  - virtually no CO2 left now, compared to what there used to be
• Describe today's atmosphere


  78% nitrogen, 21% Oxygen and other gases make up less than 1% of the atmosphere (eg water vapour and CO2)
• What is the test for oxygen?

  If a glowing spint is relit
• Describe the Greenhouse effect

  the warming of the surface and lower atmosphere of Earth that occurs when carbon dioxide, water vapor, and other gases in the air absorb and reradiate infrared radiation
• How has human activity caused climate change?

  - chopping down trees so less CO2 is absorbed

  - burning fossil fuels releases CO2

  - increasing average energy demand per person

  - increasing human population

  -livestock farming increase methane in atmosphere (produced in digestive processes)
• How can we analyse atmospheric gas levels in history?

  - analysis of gas bubbles in ice

  - fossil analysis

  - tree ring analysis (how much id they grow that year, more growth = more co2 available)
• Why do some people believe historical data about the atmosphere is invalid?

  It is taken at few location so may not be representative, and is also based on analysis leading to estimates, meaning it is not amazingly accurate