Chemistry - Unit 2d - Crude oil, Fuels and organic chemistry

Whats a non - renewable fuel?

Fuels that take so long to make that they are being used up faster than being formed

Whats a main source of hydrocarbons?

Crude oil

How is crude oil formed?

Underground over millions of years under high temperature and pressure from buried remains of marine organisms.

What kind of form are hyrocarbons usually in?

Chains or rinsg and are most likely alkanes

How are different fraction sof crude oil seperated ?

Fraction distillation - oil is heated until most of it is ga. Gases enter fractionating column. In column, theres a temp. gradient. Longer hydrocarbons have higher boiling points so turn back into liquids and drain out when there near the bottom early on. Shorter hydrocarbons have lower boiling point so drain out much later on, near the top of column where its cooler. Crude oil is now seperated into different fractions. Each fraction contains mixture of hydrocarbons with similar boiling points

How is crude oil used for modern transport?

Cars, trains, planes etc. - generating electricity

What are negatives to using crude oil?

Not sustainable with population increasing and demand for crude oil increasing

Prices for heating,transport, food etc. are affected by crude oil demand

Burning fossil fuels leads to global warming and acid rain

What is cracking?

Splitting up long-chain hydrocarbon molecules into smaller ones to build used

Heat hydrocarbons until they’re vapour and is passed over powdered catalyst, which causes them to split apart

What are alkenes used for?

Starting material when making polymers for plastic

Why are shorter hydrocarbons easy to ignite?

They have lower melting points so are gases whihc react with oxygen to produce gas misxture which burns into flames if in contact with spark

What is Viscosity?

Measurement of how easily a substance flows

Why are shoter hydrocarbons more clean-burning?

They have less carbon atoms that will be relased when burnt

Whats the colour of the flame when shorter hydrocarbons are burnt?

Blue flames

Whast the colour of the flams when a longer hydrocarbon is burnt?

yellow and smocky flames

What are the colours of a shorter hydrocarbon

colourless

What are the colours of a longer hydrocarbon?

brown

What are the colours of a medium hydrocarbon?

yellow

Why do hydrocarbons make great fuels?

They are very exothermic when reacting with oxygen

What is a complete combustion?

When the only products are carbon dioxide and water

What are pros to using hydrogen gas as fuel cell?

Very clean fuel - only waste product is water

Obtained from water which is renwable source

What are cons to using hydrogen gas as fuel cells?

Expensive engine - electrolysis of water

Hard to store as its dangerous as it forms explosive mixture with air

What are the three things a fire needs to burn?

Fuel and oxygen for combustion reaction but heat is also required as it has high activation energy

How do you measure energy released in combustion?

Put 100cm3 of water in conical flask and record temp.

Weigh spirit burner and lid

Put spirit burner underneath flask and light wick. Heat until temp. is about 40c

Put out flams using burner lid and measure final temp. of water

Weigh spirit burner and lid again

Use energy released from fuel per gram(J) formula

Whats the energy released from fuel per gram(J) formula?

= (mass of water(g) x temperature increase(c ) x 4.2(J/g/c))/Mass of fuel(g)

why do we times by 4.2?

Its the specific heat capacity of water - amount of energy required to raise temp of 1 gram of water by 1c

Whats an alkane?

Hydrocarbons - chain of carbon atoms surrounded by hydrogen atoms

Whats the genral formula for an alkane?

= CnH2n+2

Where n = no. carbon atoms in a molecule

Whats the names for structual formulae of first five alkanes?

1 - methane

2 - ethane

3 - propane

4 - butane

5 - Pentane

What does it mean if the molecules are saturated?

There are only single bonds between carbon atoms

Whats an isomer?

Two molecules are isomers of each other if they have the same molecular formula but the atoms are arranged differently

Why are Alkene different to alkanes?

They contain a double bond - unsaturated molecules that can open up to bond with other atoms. This is an addition reaction

Whats the genral formula for alkenes?

= CnH2n - they have twice as many hydrogens as carbons

What happens when a alkene reacts with a hydrogen?

Hydrogen reacts with double bond to open it up and form the equivalent, saturated, alkane . Hydrogen reacts with hcarbon in presence of catalyst

How owuld an alkene react with bromine?

Saturated bromoalkanes molecules are formed, with the bouble carbons each becoming bonded to a bromine atom

How do you test for alkenes?

Add orange-brown bromine water to saturated compound, no reaction will happen and itll stay orange brown if its an alkane

If its an alkene, it will turn to a colourless dibromo-compound

What the longest part of the carbon chain called?

parent chain

What an addition polymerisation?

Lots of unsaturated monomer molecules that open up thier bouble bonds and join to form plymer chains

What are 7 properties of plastic?

cheap, strong, less dense, flexible, easily molded, electrical insulators,resistant to corrosion

What can you use poly(ethene) for?

Carrier bags and plastic bottles because they are flexible and low densityW

What can you use Poly(propane) for?

Packing crates as its easy to mold and low density and is rigid and tough so can also be stretched into fibres for ropes

What can poly(vinylchloride) be used for?

Drainpipes and window frames because its easy to mold, durable and fire resistant

What can poly(tetrafluoroethene) be used for?

Non-stick pans because they have very high melting point and tough and almost unreactive

How do we dispose polymers using landfill sites?

load of plastic is dumped in landfill sites(plymers are too expensive or difficult to separate)

valuble land getting used up non-biodegradable

How do we dispose polymers using Combustion?

Burning plastics to generate energy for electricity. However toxic gases can be released

Carbon dioxide is produced - global warming

Advantgaes of recycling polymers

• reduces landfill

• reduces emissions

• saves money and creates jobs

Disadvantages of recycling polymers

• Can only be recycled a finite number of times

• Release dangerous gases into atomasphere which are harmful to animals and plants

• Expensive to sperate polymers before melting

How does fermentation work?

Enzymes in yeast are used to convert sugars into ethonal and carbon dioxide

How do microorganisms use alcohol as an energy source?

Use oxygen in air to oxidise alcohol which produces carboxylic aicids

What the recommended maximum number of units of alcohol per week?

14 units for both men and women

Why is ethonal used as a solvent in the industry?

Can dissolve substances water can and cant dissolve

What are benifits and drawback of Bioethanol?

Good:

Created quickly and renwable and cheaper and almost carbon neutral

Bad:

Gowing sugar can for bioethanol reduces land avaliability and its expensive to transport bioethonal and it produces carbon dioxide

How can you test if a liquid contains alcohol?

Add potassium dichromate soltuion in sulfuric acid to liquid. Heat up. If mixture turns green then it contains alcohol. If it remains orange, then it doesnt.

How do you use infrared spectroscopy?

Use to identify pressence of certain bonds in organic molecules. A beam of IR radiation is passed through sample. Bonds between different atoms absorb different frequencies of IR radiation. The frequencies are converted into wavenumbers and an IR graph called a spectrum is produced