Crude oil

What is crude oil?

Crude oil is a mixture of hydrocarbons, compounds containing carbon and hydrogen only

It is a finite, non-renewable resource

Crude oil itself has no uses and therefore it has to be separated into ___ before it can be used.

How can we do this?

Fractions

We can use fractional distillation to separate crude oil into fractions.

• This is carried out in an oil refinery

Each fraction consists of ____

groups of hydrocarbons of similar chain lengths

What determines in which fraction each hydrocarbon molecule will be separated into?

Its size and length

The size of each molecule is directly related to ____

Most of the compound in crude oil are from the same homologous series. Which one?

How many carbon and hydrogen atoms the molecule contains

Alkanes (single bonds only)

Describe how crude oil is separated into fractions by fractional distillation

• Crude oil is vapourised/heated

• The vapour enters the lower part/bottom of the column

• There is a temperature gradient in the column

  • Accept cooler at the top and hotter at the bottom

• The vapours rise up the column until they condense

• At a height where the boiling point of the vapour is lower than the temperature in the column

  • Allow the fractions are separated according to their boiling point

Further explanation:

Key point

What is another name given to the ‘boiling point’?

Condensation point

• The

Label the names and uses of the fractions obtained from crude oil

The hydrocarbons in the refinery gas fraction have very small masses and their BP are so low that the temperature of the column never falls low enough for them to condense to liquids

The temp of the column isn’t hot enough to boil some of the very large hydrocarbons found in crude oil so they remain as a liquid. These are removed as a residue from the bottom of the column

Uses of the fractions

All hydrocarbons can ___ in air to form ___ and ____ and release a lot of ___ in the process

Therefore the various fractions can be used as ___

All hydrocarbons can burn in air to form carbon dioxide and water and release a lot of heat in the process

Fuels

What is a fuel?

A fuel is a substance which, when burned, releases heat energy

What is another name given to refinery gases? Uses?

Liquefied petroleum gas

They are used for domestic heating and cooking

What is gasoline (petrol)? Uses?

As with all the other fractions, petrol is a mixture of hydrocarbons with similar boiling points

It is used for fuel for cars

Uses of kerosene?

Jet/aircraft fuel (main thingy) but also for domestic heating oil and as ‘paraffin’ for small heaters and lamps

Uses of diesel?

Fuel for buses, lorries, cars and some railway engines

Some diesel is also used for something else, what? What process does it need to undergo before?

Some is also converted to other more useful organic chemicals, including petrol in a process called cracking

Uses of fuel oil?

Used as a fuel for ships and power stations (savemyexams)/ and for industrial heating (textbook)

Uses of bitumen

It is melted and mixed with small pieces of rock for surfacing roads and roofs

In which fraction are the hydrocarbons containing up to 4 carbons?

Refinery gases are a mixture of methane, ethane, propane and butane

Trends for the main fractions of crude oil

As you go up the fractionating column, the hydrocarbons have:

• Lower boiling points

• Lower viscosity

• Colour lightens

Not in ms but yes in mr wilson’s notes and savemyexams

• Higher flammability (mr wilson)

• More volatile (savemyexams)

Explain what happens to the boiling point as the molecules get bigger

BP increases

• As the molecules get bigger, the intermolecular forces of attraction become stronger — VERY IMPORTANT PHRASE LEARN

• More energy is needed to overcome these stronger intermolecular forces of attraction

Explain what happens to the volatility as the molecules get bigger

The liquids become less volatile

• The bigger the hydrocarbon, the more slowly it evaporates at room temperature

• As the molecules get bigger, the intermolecular forces of attraction become stronger

Explain what happens to the viscosity as the molecules get bigger

The liquids become more viscous and flow less easily

• Liquids containing large molecules flow less easily because as the molecules get bigger, the intermolecular forces of attraction become stronger

What happens to the colour as the molecules get bigger?

What happens to the flammability as the molecules get bigger? What does this mean in terms of their utility?

The liquids become darker in colour

Flammability decreases (they do not burn as easily)

• This limits the use of the bigger ones as fuels

En teoría combustion (todo lo de incomplete y eso) va en este topic pero no lo he puesto aqui JIJI

Key point

• What are fossil fuels?

Fossil fuels include coal, gas and fuels derived from crude oil, which all come from things that were once alive

What are the environmental problems associated with the burning of fossil fuels from crude oil?

Most of the time they refer to ‘impurities’ so you should talk about SULFUR ONLY, however, CO2 is also released

• Releases the greenhouse gas CO2. Greenhouse gasses trap the heat radiated from the Earth’s surface (originally from the Sun) which contributes to climate change → leads to sea levels rising, etc

• Fuels from crude oil contain sulfur impurities. When the fuels are combusted, the sulfur gets oxidised and forms sulfur dioxide. Sulfur dissolves in water (reacts with water and oxygen) to form sulfuric acid and forms acid rain

Balanced chemical equations for sulfur dioxide and nitrogen dioxide to form acids.

What is acid rain?

Rain with a pH lower than 5.6 and is caused when water and O2 react with sulfur dioxide to produce sulfuric acid or with various oxides of nitrogen to give nitric acid

What is the location where they burn these fuels?

Apart from burning fuels from crude oil and releasing sulfur dioxide, what is another way that acid rain might form that is not from burning fuels? How?

Oxides of nitrogen and sulfur dioxide come mainly from power stations and factories

From car engines. The temperature reached in car engines is enough to allow nitrogen and oxygen from air to react, forming oxides of nitrogen

What is the solution to acid rain?

Removing sulfur from fuels, ‘scrubbing’ the gases from power stations and factories to remove SO₂ and NO_x and using catalytic converters in cars

Effects of acid rain

• Leeches minerals out of the soil

• Damages statues/rocks/buildings

• Damages leaves preventing photosynthesis

• Makes aquatic habitats too acidic for life