Chemistry of Materials – Flashcards
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| What are A and X in zAX |
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A: Mass number, number of electrons and neutrons B: Atomic Number, number of protons number of electrons is usually equal to protons |
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| Maximum number of electrons per orbital |
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| 2 |
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| Order of Shells |
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| 1s 2s 2p 3s 3p 4s 3d 4p |
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| Define Ionisation Energy |
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| The minimum energy required (to be added to the atom) to remove the outermost electron from the ground state of an isolated (eg. gaseous) atom |
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| In what directions Ionisation Energy increases/decreases |
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| Decreases from top to bottom Increases from left to right |
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| Three properties of ionisation energy |
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| -Increases as successive electrons are removed -Sharp increase when an inner-shell electron is removed -High values of IE are why only valence electrons are involved in bonding |
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| Define Electron Affinity |
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| The energy change that occurs when an electron is added to a gaseous atom - measures attraction of atom for the added electron |
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| Properties of Electron Affinity |
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| -Typically, energy is released when an electron is added (negative value) -Typically increases (more negative) left to right -Noble gasses are positive -typically is positive (energy gained) when the added electron begins a new shell (eg. noble gasses, Be, Mg) |
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| Define Electronegativity |
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| The ability of an atom in a molecule to attract electrons to itself |
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| In what directions Electronegativity increases/decreases |
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| Increase from left to right Decrease from top down |
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| Describe Hydrogen Bonding |
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| when the molecules in a molecular compound have both a hydrogen atom and at least one "lone pair" of electrons, the hydrogen of a molecule will be strongly attracted to the lone pair on an adjacent molecule, creating above average inter-molecular force. http://chemwiki.ucdavis.edu/Physical_Chemistry/Quantum_Mechanics/Atomic_Theory/Intermolecular_Forces/Hydrogen_Bonding |
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| Formal Charge formula |
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F = V - (N + B/2) V = Valence Electrons N = Non-Bonding Electrons B = Bonding Electrons |
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| applying formal charge |
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| The four types of solids |
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| Molecular Covalent Network Ionic Metallic |
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| Properties of Molecular Solids |
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| -Intermolecular forces are weak -Thus low melting point -Room temperature gases and liquids usually form molecular solids at low temperature |
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| Crystalline solid: |
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| well-ordered, definite arrangements of molecules, atoms or ions. Crystals have an ordered, repeated structure |
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| Amorphous solid: |
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| no ordered structure, e.g. rubber, glass |
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| Properties of Covalent Network Solids |
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| -Atoms held together in large networks by covalent bonds -Examples: diamond, graphite, quartz (SiO2), silicon carbide (SiC), and boron nitride (BN) |
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| About Carbon Nanotubes |
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| -Example of covalent network -Long cylindrical structures -Either single or multi walled -Potential structural applications in high strength materials -Applications in a range of conductive materials |
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| Properties of Ionic Solids |
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| -Regular structures, packing of positive and negative ions around each other -Hard, brittle, high melting points -Poor electrical conductors |
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| Properties of Metallic Solids/Bonding |
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| -Metal ions in a sea of delocalised valence electrons --> good electrical conductor -Strong bonding -Without any definite directions for bonds, the metals are easy to deform |
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| coordination number of simple cubic, body-centred cubic and fcc |
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| 6, 8, 12 |
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| occupation of simple cubic, body-centred cubic and fcc |
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| 52%, 68%, 74% |
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| Example of simple cubic |
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| ?-Po |
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| Examples of body-centred cubic |
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| Ba, Cr, Fe, W, alkali metals |
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| examples of fcc |
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| For example: Ag, Al, Au, Ca, Cu, Ni, Pb, Pt |
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| Images of cubic unit cells |
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| [image] |
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| For CCP, the stacking pattern that produces hexagonal close packing |
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| ABABABAB, rather than ABCABCABCABC for Cubic Close Packing |
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| picture of hexagonal close packing |
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| [image] |
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| The two packing types for FCC |
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| Hexagonal close packing Cubic close packing |
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| Differences between Hexagonal close packing and Cubic close packing |
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| Cubic: Ductile Hexagonal: Brittle |
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| Properties of Metals vs Non-Metals |
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| Metals: -Low ionisation energy rather than High -Malleable rather than usually brittle -Good electrical conductors |
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| about heterogeneous alloys |
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| components not dispersed uniformly |
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| Two types of Solution alloys |
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| -Substitutional alloys - solute atoms disperse main atoms -Interstitial alloys - solute atoms occupy empty space between main atoms |
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| about Substitutional alloys |
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| -All atoms radius within 15% of each other -Elements must have similar bonding characteristics -Elements Must have same crystal structure -Elements Must have Similar Electronegativity |
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| about Interstitial alloys |
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| -One element must have a significantly smaller radius than the other |
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| describe triple point |
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| P and T at which all three phases are in equilibrium |
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| what is abnormal about water phase diagram |
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| the solid-liquid line goes backward (i.e. solid is less dense than liquid) |
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| what is a supercritical fluid |
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| a fluid that is beyond the temperature and pressure of the critical point. has a density of liquid and viscosity of gas. |
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explain the steps: [image] |
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| Energy is released by the changing of bonds as the iron changes phase, and so the material does not overall cool down at during these phase changes. |
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| how to read binary phase diagram (picture) |
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| [image] |
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| what is silica |
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| Silicon Dioxide |
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| what is Carbonate |
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| (CO3)2- |
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| what is Silicate |
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| (SiO4)4-, tetrahedra |
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| basic steps for making portland cement |
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| [image] |
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| About setting cement |
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| -Reaction of clinker materials with water to give gelatinous calcium silicates, solid Ca(OH)2, complex silicates, calcium aluminates, etc -In concrete, the hydrated materials bind to solid aggregates (stones) -Hydration reaction of Portland cement results in hardening -There are rapid reactions within hours, and slow reactions over years |
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| a few examples of things made from petroleum/crude oil |
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| -liquid Fuels -plastics -detergents -soaps -drugs |
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| picture of crude oil reservoir |
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| [image] |
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| Elements/percentages in petroleum |
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| -Carbon 84% -Hydrogen 14% -Sulfur 1-3% -Nitrogen, oxygen, metals, salts <1% each |
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| Hydrocarbons in petroleum |
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| -Alkanes ~30% -Cycloalkanes ~50% -Aromatics ~15% |
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| General formula of alkanes |
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| CnH(2n+2) |
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| the three basic steps of crude oil before final use |
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| -Washing/desulfurisation: REMOVAL OF SALTS AND MINERAL CONTAMINANTS -Seperation: Fractional Distillation -Conversion: Reforming, Cracking, Alkylation and Isomerisation |
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| Details of fractional distillation |
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| Crude oil is heated to ~600C and blasted into a distillation tower. The fuels come out in broad fractions based on number of carbons |
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| Basics of the four conversion processes |
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| -Reforming: changes alkanes and cycloalkanes to more valuable aromatics (reformer) -Cracking(Pyrolysis): breaks large hydrocarbons to smaller ones (coker) -Alkylation: Changes alkanes and alkenes to larger branched alkanes (alkylation unit) -Isomerisation: Alters arrangement of atoms in molecule |
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| details of Reforming |
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-Uses heat, pressure and a catalyst [image] |
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| schematic of reforming unit |
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| [image] |
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| three types of cracking |
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Catalytic cracking Hydrocracking Steam/Thermal cracking |
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| about catalytic cracking |
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-Catalysts help reactions -Typically ~900C and 10-20psi -Three basic functions: --Reaction of catalyst and feedstock cracks feedstock into different hydrocarbons --catalyst is reactivated by burning off coke --new hydrocarbons are distilled into different weights |
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| Example chemical reaction of catalytic cracking |
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| C15H32 --> 2C2H4 + C3H6 + C8H18 |
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| about fluid catalytic cracking |
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| -Feedstock is vaporised and mixed with a fluidised powdered catalyst (very very fine behaves like liquid) -Carbon is deposited ON the catalyst, requiring it to be "regenerated" occasionally -Modern implementations use a continuous loop system so the process can run while catalyst is regenerated |
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| schematic of fluidised-bed cracking plant |
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| [image] |
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| about hydrocracking |
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| -Uses elevated partial pressure of hydrogen gas and catalysts -Pressure of 1000-2000 Psi -Temperature of 400-800 C -Produces only saturated products |
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| about thermal/steam cracking |
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| -Hydrocarbon diluted with steam and briefly heated in furnace without O2 -850°C, slightly above atmospheric pressure -Residence time very short in reactor # milliseconds |
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| about alkylation |
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| -Uses strong acid catalyst (sulfuric or hydrofluoric acid) and temperatures 0-30C -High ratio of alkane to alkene -Upgrades low molecular weight alkanes and alkenes to branched alkanes with increased molecular weight |
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| Example equation of alkylation |
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| [image] |
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| details of isomerisation |
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| -rearrangement of straight chain alkanes to branched alkanes -Uses hydrogen, chloride and catalyst -creates extra alkane feed for alkylation -improves the octane of straight run alkanes |
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| example euqation of isomerisation |
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| [image] |
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| Define Fuel |
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| Fuel is any material that is burned or altered to obtain energy to do work through a chemical reaction. |
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| Fuel Classification |
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| 6 classes: class 1(light) to 6(heavy) light/heavy as in length of carbon change and increase in boiling point and viscosity |
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| about virgin/straight-run gasoline |
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| not suitable for modern engines, but is the main part of the fuel blend |
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| the four stroke gasoline cycle (image) |
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| define is compression ratio |
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| is equal to V/v, V = Volume of cylinder at the bottom of the cyle v = volume of the cylinder at the top of the cycle |
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| about compression ratio |
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| -Increases efficiency, somewhat logarithmically -Modern cars R = ~9:1 -High compression ratio means fuel/air can spontaneously ignite --> knocking -knocking prevented by high octane fuel |
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| about octane number |
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| -ON measures a fuel's resistance to auto-ignition -modern cars require ON>~90 |
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| what is octane rating of straight-run gasoline |
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| ~60 |
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| how Octane Number is measured |
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| -Measured in a test engine -iso-octane has the benchmark ON of 100 -n-heptane (plain C7H16) has ON of 0 e.g. gasoline with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90 |
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| how octane ratingincreases for different hydrocarbans |
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| tyeps of fuel additives |
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| Anti-knock Lead replacement antioxidants de-icers rust inhibitors |
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| about anti-knock additives |
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| -lead is a cheap anti-knock additive, but obvious health dangers AND incompatibility with catalytic converters -lead replaced by hydrocarbons of higher octane rating |
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| about antioxidant additives |
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| -often amines -prevent build up of gum, which can lead to engine damage and performance decrease |
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| about cetane number |
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| -opposite of octane number -measures ease at which fuel will undergo compression ignition -for typical use CN = ~50 |
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| approximate carbon chain length of gasoline |
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| 4-12 |
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| approximate carbon chain length of diesel |
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| 8-21 |
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| what is biodiesel primarily made of |
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| triglycerides - triesters of glycerol with 3 long chain fatty acids |
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| reaction for production of biodeisel |
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| TRANSESTERIFICATION triglyceride + Methanol --> Biodiesel + Glycerin |
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| advantages/disadvantages of biodiesel |
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| -Works in most diesel engines, Sustainable, less pollutants than fossil fuel, safer to handle than fossil fuels -Can be problematic in some engines, lower fuel economy than fossil fuel |
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| blending of biodiesel |
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| Can be used pure of blended with petroleum "B-factor": 100% biodiesel is referred to as B100; 20% biodiesel = B20 |
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| What is an explosive |
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| Substance containing a tremendousamount of poten0al energy stored in chemical bonds. |
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| what makes an explosion |
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| rapid release/expansion of gasses -> pressure production of heat quick release of energy produces more stable substances (mainly gasses) |
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| difference between fuels and explosives |
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| Fuels react in a controlled manner explosives react rapidly and violently |
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| define high explosive. examples |
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| speed of reaction is faster than the speed of sound Dynamite, TNT, plastic explosives |
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| define low explosive. example |
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| speed of reaction slower than speed of sound Black Powder |
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| Two useful specification tests for explosives, units |
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| Explosive Strength (cal/qty) velocity of Detonation (m/s) |
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| Trauzl test - brief description |
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| 10g of explosive is placed in a cavity in a lead block, covered with sand and then detonated. Resulting volume of cavity is compared to the Standard Volume produced by gelignite |
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| basic methods of determining velocity of detonation |
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| optical or electrical |
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| an explosive may consist of either: |
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| a chemically pure compound a mixutre of fuel and oxidzer |
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| common oxidizers |
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| ammonium"nitrate,"sodium"nitrate,"calcium"nitrate |
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| two necessary structural features of molecular explosives |
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| at least on chemical bond that can easily be broken A high proportion of oxygen required for explosion within the molecule itself |
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| examples of weak bonds for molecular explosives |
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| N-O N-N N-Cl O-Cl |
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| about oxygen balance |
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| indicates degree to which an explosive can be oxidised -Zero: exactly enough oxygen -Positive: more than enough oxygen -Negative: Not enough oxygen Maximum explosiveness as oxygen balance approaches zero |
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| how to tell if reaction has positive or negative oxygen balance |
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| Pos: O2 produced Neg: C or CO produced |
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| about primary explosives. Example |
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| -Very powerful -Very sensitive -Usually used as only a detonator -Mercury Fulminate |
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| About Secondary Explosives. Example |
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| -aka high explosives -Most explosives are secondary explosives -nitroglycerin -PETN - Benchmark. More explosive than PETN in primary explosive -RDX -Semtex |
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| About tertiary explosives. Example |
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| -Not explosive unless mixed with other combustibles. -Inexpensive -must be detonated by secondary explosives -ANFO (Ammonium Nitrate + Fuel Oils) |
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| Use of explosive mixture allows control of |
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| -Strength -V.O.D. -Cost -Safety |
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| what is a polymer |
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| made up of many repeating monomers. High molecular weight |
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| Polymerisation |
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| the process of linking monomers |
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| advantages of polymers |
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| -Ease of processing -Light Weight -Tough -Low Friction -Flame retardant -Insulating -Appearance -Weather/chemical resistance |
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| how increasing polymer chain length affects physical properties |
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| as chain length increases: -melting and boiling point increase -impact resistance increases -viscosity increases -chain mobility decreases -strength and toughness increase |
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| how polymer branching affects physical properties |
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| can be linear, branched, cross-linked affects chain packing and polymer density |
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| how interchain interactions affects physical properties |
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| -Interaction of chains through hydrogen bonding etc, -rotation of carbon bonds -affects strength and rigidity |
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| about polymer non-uniform/disordered packing |
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| -amorphous -less rigid - malleable -weaker |
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| about polymer crystalline packing |
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| - crystalline-like -increased regidity, strength and opactity -more brittle |
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| about vulcanisation |
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| vulcanisation: to natrual rubber heat and add sulfur. sulfur cross-links to make more rigid. 30% cross-linking is very rigid rubber. |
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| Glass transition temperature |
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| the temperature at which the transitionin the amorphous regions between glassy and rubbery occurs |
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| How chain mobility affects Tg |
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| more immobile chain --> higher Tg |
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| How chain length affects Tg |
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| Tg increases with increasing chain length |
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| about plasticisers |
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| -can be added to a polymer -increase rubberyness of polymer -decreaes Tg |
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| atactic side chains |
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| side chains are randomly distributed |
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| isotactic side chains |
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| side chains are all on the same side |
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| syndiotactic side chains |
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| side chains are on alternating sides |
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| five factors affecting Tg: |
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| -stiffer chain groups raise Tg -strong intermolecular forces raise Tg -side group restrict rotation, raise Tg -cross linking raises Tg -plasticisers lower Tg |
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| how to identify addition polymer |
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| the repeating unit is always the same as the monomer from which the polymer is made |
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| The four addition polymerisation procedures |
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| -Radical Polymerisation -Cationic Polymerisation -Anionic Polymerisation -Coordination Polymerisation |
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| General characteristics of radical addition polymerisation |
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| -Polymer chains form rapidly -Extremely Exothermic -Branching and cross-linking is common |
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| what is copolymer |
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| polymer with more than one repeating monomer |
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| statistical copolymer |
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| different monomers are distributed randomly |
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| alternating copolymer |
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| different monomers are alternating ABABABABABABAB |
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| block copolymers |
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| different monomers occur in blocks AAAAAABBBBBBBAAAAAAAAAAAAAAABBBBBAAA |
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| graft copolymers |
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| one monomer is main chain, another is a side chain |
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| about ABS |
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| -very tough and strong |
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| about SBR Styrene Butadine Rubber |
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| -tyres, chewing gum -replacement for natural rubber |
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| applications of polyamides |
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| -heat resistant -strong synthetic fibres -aerospace -military -kevlar |
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| about epoxy-resins |
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| -strongest known adhesives -chemical and heat resistant |
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| about dental polymers |
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| slowly begin to cross-link, so time to shape around teeth |
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| about thermoplastic polymers |
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| -can be heated to softening without degradation -not cross-linked -difunctional monomers |
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| about thermosetting polymers |
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| -very hard and rigid once formed -degrade when melted -highly cross-linked |
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| examples of thermoplastics |
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| Nylon, polystyrene |
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| about bioplastics |
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| -made from renewable biomass can degrade... |
