Petroleum C, D Petroleum As An Energy Source

Human use of petroleum dates back 5,000 years It was used to waterproof ships, pave roads, and obtain kerosene for lamps.

C.2 Energy: Past, Present, and Future The sun is our planet’s primary energy source. Through photosynthesis, plants change CO 2 into glucose and oxygen with the following reaction: 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 The energy from the glucose is stored in organic molecules found in plants and animals, called biomolecules. Y.T. pgs

C.3 Energy and Fossil Fuels Fossil fuels can be regarded as forms of buried sunshine because they probably originated from prehistoric plants and animals. The energy released by fossil fuels was originally “captured” by the prehistoric plants.

Combustion Reaction When fossil fuels are burned, it’s called combustion. A combustion reaction is: CH 4 + 2O 2  CO 2 + 2H 2 O + energy The fuel burns in the presence of oxygen and always produces carbon dioxide, water and energy.

C.3 Energy and Fossil Fuels When fossil fuels are burned, they produce energy that exits the substance. This reaction is called an exothermic change. An endothermic change is a reaction where energy is absorbed into the system.

Law of Conservation of Energy Energy cannot be created or destroyed. The total energy of the universe is constant. Things don’t run out of energy, the energy is transformed into something else.

Energy Conversions Fossil-fueled plants use oil, coal or gas in the generation of electricity (see diagram 1). Combusting, or burning fuel creates heat (2), heat turns water to steam (3), steam turns a turbine (4), the turbine spins the generator (5), creating electricity (6). The steam is then condensed by cool water drawn from a nearby source (such as rivers). This cooling water, which is kept inside in tubes, is returned to its source without any contamination. The steam water stays in its own closed system and is returned to the boiler to start the process again.

Energy Conversions To run a hairdryer, the following energy conversions would occur Chemical energy  Thermal energy  Mechanical energy  Electrical energy  ____?______energy + ____?_____ energy + ____?______energy

Even the most well maintained gasoline powered car engine is only 25% efficient. Out of every $10.00 of gas you put in, only $2.50 actually runs the car.

Hybrid Cars Honda Insight is currently the most fuel efficient car in the U.S., getting 60 mpg. Some hybrid cars are gasoline-electric cars. The engine is smaller which reduces pollution and increases efficiency. The electric motor acts as a motor and electric generator to recharge batteries. The motor can draw energy from the batteries to accelerate the car.

Heats of Combustion The quantity of thermal energy given off when a substance burns is called its heat of combustion. When one mole of a substance is burned, the thermal energy released is called its molar heat of combustion.

Specific Heat Specific heat is the amount of energy it takes to heat up one gram of a substance one degree Celsius. The specific heat for water is 4.18 J/g o C Calculate the amount of energy it would take to raise the temperature of 4.5 grams of water 20 o C. E = g x ΔT x S.H.

C.6 Using Heats of Combustion Use table 5, page 201. Calculate the amount of energy produced by combusting ethane. C 2 H 6 + O 2  CO 2 + H 2 O + thermal energy. 1 st balance the equation. 2 nd Determine number of moles of ethane from balanced equation. 3 rd Take number of moles and multiply by the molar heat of combustion. Your Turn pg 202.

C.7 Altering Fuels--Cracking The process of cracking is used to break down hydrocarbons into smaller molecules. Cracking molecules can be accomplished by heating the hydrocarbons and breaking them into smaller fractions. Fuel fractions can be isomerized to produce branched molecules that burn more efficiently in car engines.

Product molecules that are 5 to 12 carbons are the most useful components of gasoline. Catalysts are also added to increase the rate of reaction without affecting the overall chemical reaction

Catalytic cracking is more useful because it can occur at much lower temperatures and increasing energy efficiency. More than a third of all crude oil undergoes cracking. “Cat” Cracker

Ratings Octane ratings are an average of the RON (research octane number obtained from city driving) and MON (motor octane number obtained from interstate driving). These two numbers are averaged together. For instance, if the RON is 93 and the MON is 92, the octane rating is 92.

. The octane scale assigns the branched- chain hydrocarbon commonly called isooctane an octane number of 100. Straight-chain heptane is assigned an octane number of zero because of its poor performance as a fuel. Combustion of heptane

Lead-based gasoline was eradicated in 1975 due to its harmful effect on the environment. Oxygenated fuels are now blended with gasoline to enhance its octane rating.

While oxygenated fuels do not produce as much energy as regular gasoline hydrocarbons, they do reduce pollution and increase the octane ratings. Two common oxygenated fuels are methanol and methyl- t-butyl ether (MTBE).

Current U.S. production of MTBE is over 4 billion gallons and one of the top ten industrial chemicals. Recent concerns are that it is getting into groundwater and contaminating water sources. Flexible fuel cars can run on methanol, gasoline or mixtures of the two. Methanol can be produced from natural gas, corn, coal or wood and helps conserve non-renewable resources.

Gasohol is a mixture of 10% alcohol and 90% gasoline. The general formula, R-O-R ‘ represents oxygenated hydrocarbons. Your Turn pg 206, Pt. C Sum Questions pg

D Useful Materials from Petroleum In alkane molecules, each carbon is bonded to four other atoms. This is called a saturated molecule. In alkenes, the carbon atom bonds to three other atoms with double bonds forming an unsaturated molecule. Lab pg 210.

More Isomers The double bond in alkenes prevents the carbons from rotating around the bond axis. This creates a cis- trans isomerism. Cis means the arrangement of atoms is the same side on both sides. Trans means they’re not the same on each side.

More Builder Molecules Cycloalkanes are saturated hydrocarbons where the carbon atoms are joined in rings. In naming, use the alkane—in this case, pentane and add the prefix cyclo. This is a cyclopentane .

There are also unsaturated rings, called aromatic rings. Notice the double bonds on every other carbon. Aromatics are formed during fractionation and cracking. Aromatics are also used for dye and drug manufacturing.

D.4 Builder Molecules Containing Oxygen Functional groups determine what molecules there are. Alcohols have the group: R-OH like methanol: CH 3 OH In naming alcohols, take the root propan and add ol for propanol.

Carboxylic acids have a double bonded oxygen and an OH group on the end carbon. Two carbons with this group would be called an ethanoic acid. C 2 H 3 OH or CH 3 COOH This is also called acetic acid.

Petrochemicals are synthetically produced chemicals created from oil or natural gas. Examples include detergents, pesticides, medicines, cosmetics, paints, fabrics, rubber and foam.

Esters have a double bonded oxygen and carbon with a single bonded oxygen also attached to the carbon. Root name ends in yl (methyl) Second name is acetate. Example: methyl acetate would have 1 carbon attached to the single and double bonded oxygens. To the right is a three carbon molecule. What’s its name?

D.5 Creating New Options: Petrochemicals Alkenes and aromatics are important builder molecules. Ethene and propene are especially important.

Addition Reaction Ethene + Water will produce ethanol. C 2 H 4 + H 2 O  C 2 H 5 OH

Polyvinyl Chloride Chains of CH 3 Cl link together to make long chains of polyvinyl chloride molecules. This is PVC plastic.

Polystyrene Styrene molecules are linked together to form polystyrene molecules. It makes an inexpensive and hard plastic used to make drinking cups and parts in cars.

Addition Polymers Addition polymers are many small units called monomers that are linked together to form a polymer.

Strength of Polymers Polymers can be made more flexible by adding molecules that act as lubricants. By creating cross- linking chains, polymers can be made into a more rigid, durable material. Which is more flexible, a rubber band or an automobile tire?

Condensation reactions Condensation reactions form polymers through the loss of small molecules such as water. These water molecules come from adjacent monomers. Example: When protein, cellulose and synthetic polymers are combined the products are nylon and polyester.