L.O: To know how crude oil can be separated into fractions

A. It has a boiling point of 170°C

B. It has a boiling point of 60°C

C. It has a boiling point of 290°C

D. It is flammable

E. It is highly flammable

F. It is not flammable

G. It is quite a runny liquid

H. It is a very viscous liquid

I. It is a viscous liquid

J. It is a very reactive molecule

K. It is quite reactive

L. It is the least reactive hydrocarbon

1

2

3

In general, the bigger the molecule the higher the boiling point.Using the graph, estimate the size range of the molecules present in each fraction

No. Carbon atoms

B.Pt

(oC)

Fraction Boiling Range

(oC)

Number of

carbons

Fuel gas Below 40

Petrol 40 - 175

Kerosine 150 - 240

Diesel 220 - 275

1-5

5-10

9-14

13-17

Fractional Distillation

Fuel gas

Petrol / gasoline

Naphtha

Paraffin / Kerosine

Diesel fuel

Fuel and lubricating oil

Bitumen

Burned in the refinery to fuel the distillation process, sold as LPG, purified and sold as bottled camping gas

Fuel for cars and motorcycles, also used to make chemicals.

Used to make chemicals.

Fuel for greenhouse heaters and jet engines, manufacture of chemicals.

Fuel for lorries, trains.

Fuel for the heating systems of large buildings, fuel for ships, lubricating oil.

Roofing, and road surfaces.

Uses of each fraction

1. Place about a 2 cm3 depth of mineral fibre in the bottom of the side-arm test-tube. Add about 2 cm3 of crude oil alternative to this, using the teat-pipette.

2. Clamp the side-arm flask over the bunsen burner. Heat the bottom of the side-arm test-tube gently, Watch the thermometer.

3. Collect the first fraction as it condenses from the equipment in the first test tube of the block. When the temperature reaches 100°C move the block to the next test tube and start collecting a new fraction.

4. Collect three further fractions, to give the fractions as follows:

100–150°C151–200°C201–250°C251–300°C

5. Test the five fractions for viscosity (how easily do they pour?), colour, smell and flammablility, and colour of smoke. To test the smell, gently waft the smell towards you with your hand. To test for flammablility, pour onto a tin lid and light the fraction with a burning splint. The smoke colour can be carefully tested by holding white paper above the smoke, any deposits will appear on the paper.

Small hydrocarbon molecules are gases or transparent liquids.

As the molecules get larger the colour becomes increasingly yellow through to the brown/black colour of bitumen used on roads and roof repairs.

Increasing size of molecules

Long molecules are very viscous (not runny) because the long chains get tangled

In contrast, small molecules are more spherical and tend not to get tangled, this makes them runny

Bigger molecules

Higher viscosity

“Treacly”

Smaller molecules

Lower viscosity

“Runny”

Longer chain hydrocarbons are more difficult to ignite

Longer chain hydrocarbons produce smokier flames as more incomplete combustion is occuring

Orange Bromine water turns colourless with

Unsaturated hydrocarbons

Bromine water stays orange in saturated hydrocarbons

Annotate your fractional distillation diagram, you must include an explanation of what is happening and the uses of each fraction (use the next slide to help with this)

Different fractions will vary in their ability to ignite, can you correctly match the substances?

Substance Ignition temperature

Kerosine <23

Petrol 85 - 150

Fuel Oil 23 - 61

Here are the viscosities of 5 hydrocarbons. The higher the value the less runny the hydrocarbon is. Draw arrows joining the hydrocarbon with the appropriate value.

Hydrocarbon Viscosity (cP)

Pentane - C5H12 0.40

Hexane - C6H12 0.52

Heptane - C7H16 0.24

Octane - C8H18 0.92

Decane - C10H22 0.70

Using viscosity data for crude oil from different areas of the world, arrange the oils putting those with the smallest molecules first.

Crude Order Viscosity (cSt)

Saudi Arabia 47.7

UK (Brent) 6.13

Norway (Gulifaks) 16.5

Alaskan 31.5

Malaysian 3.431

2

3

4

5