how does grades of coal differ?
different percentage of coal => with less carbon = less energy
different amounts impurities => when burning, more pollutants are getting out (SO2, NO2)
drawbacks to coal
(1) the dangers to the workers who mine it
(2) the environmental harm caused by coal mining, especially to waterways
(3) the pollutants it releases when burned, including mercury and sulfur dioxide
(4) the carbon dioxide it releases when burned, a greenhouse gas.
how do hydrocarbons differ and are the same ?
all of the elements hydrogen and carbon
all insoluble in water
all are flammable
all have different amounts of carbons/ hydrogen => double bonds
all have different boiling / melting points
different fundamental states
smaller one / less carbon => more volatile
use for gases
use for liquids
use for solids
can be cracked (catalytically cracking) and form new other substances
waxes and asphalt
Why is it important to lower the engine knocking
Knocking produces an objectionable pinging sound, reduced engine power, overheating, and possible engine damage.
Definition of the Word:
=> Energy that flows from a hotter to a colder object
=> quantity of energy dependent on mass and energy
=> it is measurable and transferable
Definition of the Word:
=> determines the direction of heat flow
=> a measurement of the relative kinetic energy of the particles
Definition of the:
The first law of thermodynamics
=> The energy of the universe is constant, or, energy can neither be created nor destroyed
Definition of the term:
energy due to position or composition
=> a stone at 20 m height has more potential energy than a stone in 10 m height => Gravity energy that a body has due to its height position
The Second law of thermodynamics
=> The entropy of the universe is increasing
=> Entropy is the randomness
Power Plant Efficiency -Calculation
Net efficiency = (electrical energy produced * 100) : heat from fuel
=> no electric power plant can completely convert one type of energy into another => some is transferred into useless heat. The higher the temperature of the seam, the more efficient the power plant
=> efficiency: usable energy out: total energy in
Units of Heat
Joule (J) = 1 J is the amount of energy required to raise a 1 kg object 10 cm against the force of gravity
Calorie: 1 cal is the amount of heat required to raise the temperature of 2g of water by 1°C
1 Calorie = 4,184 J
1 kcal = 1000 cal = 1 Cal
General formular of Coal
Coal is a complex mixture of substances.
=> Although not a single compound, coal can be approximated by the chemical formula
What is crude oil:
i. How is it purified (distillation tower)?
Crude oil means a mixture of hydrocarbons that exists in liquid phase in natural underground reservoirs and remains liquid at atmospheric pressure after passing through surface separating facilities.
=> may also contain sulphur, mercury and other pollutants (use of clean coal technology)
=> because of the fact that crude oil contains hydrocarbons with different carbon-chain-length, the use of a distillation tower helps to separate them
=> things with a lower boiling and melting point are higher than the other ones
converting crude oil
=> With catalytic cracking (contains heat) long chains can be cut into smaller ones
o Heat the large tar molecules until they fall apart into simpler molecules
=> Supply some help: Catalyst => they can often promote changes in the branching patters
o Catalyst are leading to more branches and therefore leading to higher octane numer
o This is important since straight-run (no chains) gasoline is only 50-55 octane. This is too low for our medium compression automobile engines.
What is the octane number?
Octane number: is a measure of the resistance of gasoline to pre-ignition in a spark-ignition internal combustion engine
o Octane number of gasoline is the percent of iso-octane in a solution of heptane that has the same anti-knocking properties as the test gasoline.
o gasoline with the same knocking characteristics as a mixture of 80% iso-octane and 20% heptane would have an octane rating of 80.
=> Elimination of octane-enhancing tetraethyl lead (TEL) in 1990’s created a need to find substitutes
o MTBE and Ethanol
=> Human health effects of exposure to MTBE are not known, but it is a greenhouse gas
=> Ethanol is a problem, because it is distillated out of plants. Since there are a lot of people who are facing poorness and cant afford eat, it is considered dubious
Natural gas: What is it?
=> methane, produced by organisms or from buried organic material, is the major component of natural gas
=> colorless, odorless (adding of sulfur dihydrogen)
=> greenhouse gas
=> use: fuels, chemical feedstock for chemical reactions
Natural gas: how is it collected (ie, fracking)?
Methane hydrates - ice-like rocks that contain methane
=> stable under the ocean but if warmed or depressurized, will release methane to the atmosphere
=> hydraulic fracturing is used to access oil and gas resources that are locked in non-porous rocks
=> high pressure fracking fluid opens networks of fractures in the shale. Sand props the fractures open
=>Holes in the well casing allow fluid to exit and gas to enter
=> The gas flows from the fractures into the pipe => methane can possible flow into the table water
Exothermic reaction: If Energy in – Energy out is a negative value => more energy released as bonds form
Endothermic reactions: If Energy in – Energy out is a positive value => takes more energy to break bonds
Chemical bonds - energy
=> The energy between two atoms, that are connected with a bond is the highest => it takes energy to break the bonds (energy is stored in the bond). As far as two atoms get from each other, es less energy is between them
=> Bond energy:
o Energy required to break chemical bonds
o Energy released when bonds form as atoms become more stable within molecules
=> higher bond energy => stronger bonds
=> energy stored as chemical potential energy
Heat of formation
standard heat of formation
the amount of heat absorbed or evolved when one mole of a compound is formed from its constituent elements, each substance being in its normal physical state (gas, liquid, or solid).