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Ziad Naser Eddin

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  1. ok seriously what was up with Paper 2 of the exam? it was so ****ing hard i chose questions 7 and 8, and btw, what is the equilibrium constant in question 1?
  2. FYI : The Palestinian senior who was shot "Nadeem Nowarah" was shot during a peaceful protest, he was NOT throwing stones NOR was he using any weapon of any kind, he was a 16 year-old kid and he was shot 5 times through the back, and straight through the heart, he did not show any signs of threat, but the IDF decided to shoot him instantaneously, meaning to kill him, a 16 year old child, he had a bright future ahead of him. + The "guerilla" you're talking about, is called a Palestinian Kofeyyeh, it represents the Palestinians and their homeland, not terrorism, say what you will, and i do not intend to disrespect anyone, but what happened to Nadeem was unjustified and we all know it! btw, The ratio of Israelis Killed " Palestinians killed 1 : 4.5 (20,000 : 90,000), nevermind the lands stolen and other unregistered killings...
  3. Friends Schools May 2014
  4. Hey Everyone, just wanted to ask is it easy to get a 7 in Psychology SL? if not, then what are the chances of someone failing in it? i'm guessing pretty low since the scale is VERY LOW it's our first year taking psychology at our school? will the examiners cut us some slack?
  5. Chemistry HL Definitions Chapter 12 Orbital: the region which describes the three dimensional shape where there is a high probability that the electron will be located. Pauli exclusion principle: it states that no two electrons in the same atom can have exactly the same four quantum numbers and hence each orbital can contain a maximum of only two electrons. Aufbau Principle: It states that when building up the electronic structure, the lowest available energy levels (those that are closest to the nucleus) are always filled with electrons first or the orbitals with the lowest energy are filled first. The resulting electron configuration will have the lowest energy configuration possible. The resulting electron configuration is called the ground state (lowest energy configuration). Hund’s Rule: It states that electrons occupy orbitals of equal energy singly before they are paired up or orbitals within the same sub-level are filled singly first.Electrons entering a sub - level with many orbitals, will spread over the available orbitals with their spins in the same direction. After that the electrons are paired and the second electron will have an opposite spin. Valence Shell: it Includes all the sub-levels of the highest energy level, in addition to any partially filled sub - levels in the lower energy levels. All the electrons in the valence shell are called the valence electrons. ---------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 13 Transition element: is defined as an element that has an incomplete d sub-level in one or more of its oxidation states Ligands: are defined as neutral molecules or anions which contain a non–bonding pair of electrons and able to form coordinate or dative covalent bonds to a central atom, central cation or a central metal ion to form a complex. Coordination number: the number of lone pairs bonded to the metal ion. ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 14 Sigma bond: is formed from the head–to–head (axial) overlap of atomic or hybrid orbitals on different atoms along the internuclear axis (line drawn through the two nuclei) where the electron density is concentrated along the line joining the two bonded nuclei (the electron distribution has axial symmetry around the axis joining the two nuclei). pi bond: is formed by the sideways overlap of two parallel p orbitals and that has the electron density concentrated above and below the internuclear axis (line drawn through the two nuclei) producing two regions of electron density. Hybridization: is defined as mixing or merging or combining of atomic orbitals to form same number of new ones of equal energy (but lower in energy than the original oribitals) for bonding. Delocalization: is defined as when pi electrons are not confined to two adjacent bonding atoms but extend over three or more atoms. Resonance structures: When writing the Lewis structures for some molecules, it is possible to write more than one correct structure. Resonance structures can be explained by the delocalization of pi electrons. --------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 15 Standard state: the standard state of an element or a compound is its most stable state under the specific conditions, For example, standard stae of H2O at 298 K is H2O(l). The Standard enthalpy change of formation, ∆HӨf, of a compound is defined as the enthalpy change when one mole of the compound is formed from its elements in their standard states at 298 K (25 oC) and 1.01 X 102 KPa (1 atm pressure). Entropy, S, is defined as the degree (is a measure) of disorder or randomness of particles of a substance. The standard entropy of a substance (also called absolute value of the entropy of a substance), SӨ, is defined as the quantity or degree of disorder or randomness owned by a mole of an element or a compound in its standard state at 298 K (25 oC). The entropy change (∆S) is defined as the change in degree of disorder of system. The standard entropy change (∆SӨ) is defined as the change in degree of disorder of system measured under standard conditions – pressure 1.01 X 102 KPa (1 atm pressure), temperature 298 K (25 oC). Gibbs free energy change (∆G): which is a thermodynamic function can be used to predict reaction spontaneity, Standard Gibbs free energy change (∆GӨ): which is a thermodynamic function can be used to predict reaction spontaneity, measured under standard conditions – pressure 1.01 X 102 KPa (1 atm pressure), temperature 298 K (25 oC). The standard free energy change of formation (∆GӨf): is defined as the standard free energy change during the formation of one mole of a substance in its standard state from its constituent elements in their standard states. Lattice enthalpy: is defined as the energy required to change 1 mole of the crystal of a solid ionic compound into gaseous ions or vice versa. So, it relates either to the endothermic process of turning a crystalline solid into its gaseous ions or to the exothermic process of turning gaseous ions into a crystalline solid. Endothermic: MX (s) → M+1 (g) + X-1 (g) Exothermic: M+1 (g) + X-1 (g) → MX (s) Electron affinity: The energy change that occurs when an electron is added to a gaseous atom or ion. X (g) + e-1® X-1 (g) The standard enthalpy of atomization is the standard enthalpy change when one mole of gaseous atoms is formed from the element in its standard state. For diatomic molecules this is equal to half the bond enthalpy. It is endothermic. It has a positive value. ----------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 16 Order of the reaction is defined as: the power of a reactant’s concentration in the rate equation. Overall order of the reaction is defined as: the sum of powers of concentration terms in the rate expression. Rate constant (velocity) constant), k: is defined as the constant of proportionality. It is constant for the same reaction at the same temperature. It is independent on the Post by: Aboo and . It is temperature dependent. Its value changes only when T of the reaction changes. The units of k depend on the overall order of the reaction. As temperature (T) increases the value of rate constant (k) increases exponentially (nonlinearly). Reaction mechanism: The simple stages (a series of simple steps) by which a chemical reaction occurs. The Arrhenius constant (A): It is a proportionality constant. It is related to the orientation of the reactants at the point of collision or it is related to the geometric requirements of the collisions: It must have the same units as k Rate Determining Step (RDS): It is defined as the slowest step in the reaction which has the highest value for activation energy (Ea). Rate of overall reaction =Rate of rate determining step Molecularity: The number of reactant molecules taking part in the slowest or the rate determining step of the reaction. Unimolecular process: a single species is reacting (number of reacting molecules is one) Bimolecular process: two species are reacting (number of reacting molecules is two) can collide and interact. Transition state (Activated Complex): It is defined as a species produced during the reaction that cannot be isolated and in which bonds are in the process of being formed and broken. An activated complex breaks down to form either the products or reform the original reactants. It occurs at an enthalpy maximum. Intermediates: these are substances that are produced in one step and then consumed in another. They do not appear in the overall equation of the reaction. The intermediate is a reactant or a product and it is not an activated complex because it occurs at an enthalpy minimum. ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 17 The vapor pressure of the liquid: the pressure exerted by the particles in the vapor phase. The enthalpy of vaporization (∆Hvap): the quantity of energy that must be supplied to 1 mol of liquid to convert it to a vapor at the same temperature. The normal boiling point: is the temperature at which the vapor pressure is equal to standard atmospheric pressure (101 KPa). ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 18 Buffer solution is defined as a solution which resists changes in pH when small amounts of strong acid or base are added to it. Acidic buffer solution: It is composed of a weak acid and its salt (its conjugate base). It has a pH < 7 Basic buffer solution: It is composed of a weak base and its salt (its conjugate acid). It has a pH > 7 Equivalence point: yhe point in titration curve when the acid and the base are present in equal amounts and the [H3O+1] = [OH-1] ( only for Titration of Strong acid and strong base). The end point is defined as the point at which color change occurs by the indicator. The role of an indicator in the titration of an acid with a base is to signal the end – point (or equivalence point) by changing color. ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 19 The standard cell potential, Eοcell, is defined as the voltage that is measured when all of the reactants and products in the redox reaction are in their standard states; i.e., solids, liquids, and gases in the pure state at 1 atmosphere or 1.01 X 105 Pa of pressure, and solutes present at a concentration of 1 mol dm-3 at 25 oC or 298 K. The standard electrode potential of an element is defined as the potential voltage difference between the element and its ions and a hydrogen electrode under standard conditions: the concentration of each ion present in the solutions is 1 mol dm-3 and the temperature of each solution is 25 oC or 298 K and the pressure is 1 atm or 1.01 X 105 Pa. Spontaneous reaction: a reaction that occurs without adding energy (beyond that required to overcome energy barrier) and gives out (Gibbs Free) energy that can do work so ΔG for this reaction has a negative value; NonSpontaneous reaction: a reaction that does not occur without adding energy and does not give out (Gibbs Free) energy that can do work so ΔG for this reaction has a positive value ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 20 Elimination reaction: When sodium hydroxide dissolved in hot ethanol is added to the halogenoalkane, and the mixture is heated under reflux, elimination of hydrogen bromide occurs to produce an alkene. The hydroxide ion acts as a base, a proton acceptor. Condensation polymerization: if each of the reacting molecules contains two functional groups that can undergo condensation, then the condensation can continue to form a polymer. The structural features of the monomers required to form a condensation polymer is the need for two functional groups at each end of the two monomers. Stereoisomers have the same molecular formula and structural formula but their atoms are arranged differently in space (different spacial arrangement). In stereoisomers each atom is bonded to the same atoms, but the way in which they are bonded is different. They are divided into geometric and optical isomers. Geometrical isomerism: the same molecular formula and structural formula but their atoms are arranged differently in space (different spacial arrangement).Geometrical isomerism occurs when rotation about a double bond or a cyclic structure is restricted or prevented. The bonds are unable to rotate freely. Restricted rotation: when rotation about a bond is restricted or prevented. The bonds are unable to rotate freely. This occurs in Geometrical isomerism. Optical isomers (Enantiomers) are defined as two mirror images of the same molecule or of each other which differ by only the arrangement of atoms in space and they can rotate plane polarized light in opposite directions. Enantiomers have similar physical properties. They only differ in one physical property called optical activity. Chiral molecule: It is defined as a molecule that contains a carbon atom bonded to four different groups or atoms. As a result the molecule and its mirror image are not superimposable. Chiral centre or asymmetric carbon: the carbon atom that is bonded to four different groups or atoms. Racemic mixture: both enantiomers are present in equal amounts, the two rotations cancel each other out and the mixture appears to be optically inactive. Achiral molecule: A molecule that contains a carbon atom bonded to four groups or atoms at least two of them are similar. As a result the molecule and its mirror image are superimposable. The molecule does not contain a chiral centre Achiral centre: the carbon atom that bears four groups or atoms at least two of them are similar. Optical activity is the ability to rotate the plane of polarized light in opposite directions. Polarimeter: the laboratory device used to measure optical activity.
  6. Chemistry SL Definitions Chapter One: Mole: is defined as the amount of substance that contains 6.02 X 1023 particles of that substance. Avogadro’s constant (L): the number of particles in one mole of substance which equals 6.02 X 1023 is called. It could be used with any particle, like atoms, molecules, protons, electrons, neutrons, positive ions, negative ions or formula units (used with ionic compounds). The relative atomic mass, RAM or Ar, of an element is defined as the weighted mean mass of all the naturally occurring isotopes of an element relative to one twelfth of the mass of a carbon – 12 atom. It has no unit. The relative molecular mass, RMM or Mr, is defined as the average mass of a molecule compared to one twelfth of the mass of one atom of carbon – 12. It has no unit. The molar mass, symbol, M: is defined as the mass of one mole of a substance. Unit is g mol-1. The molecular formula: the formula which shows the actual number of atoms of each element in a molecule of f The empirical formula: the formula which shows the simplest whole number ratio of atoms of each element in a particle of the substance. Solution: is a solute dissolved in a solvent. Solute: is the dissolved substance. Solvent: is the substance that does the dissolving. Concentration: is the amount of solute dissolved in a known volume of solution. ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 11 Precision: refers to how close several experimental measurements of the same quantity are to each other. Accuracy refers to how close a precise reading is to the true value (or the generally accepted or literature value). Systematic errors: are due to identifiable causes and can, in principle, be identified, quantified and, if possible, eliminated. Errors of this type usually result in measured values that are consistently too high or too low. These errors may be due to the apparatus itself, or they may be due to the way in which the readings are taken. Random errors: they occur if there is an equal probability of the reading being high or low from one measurement to the next. Random errors are due to chance variations over which you, as a student, have little or no control. They cannot always be identified. Because they are random, they can be reduced through repeated measurements, whereas repeated measurements will not reduce a systematic error. ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter Two: The atomic number (Z) = the number of protons in the nucleus of the atom. The mass number (A) = the number of protons and neutrons in the nucleus of the atom. Isotopes: are atoms of the same element having the same number of protons or the same atomic number but having different numbers of neutrons or different mass numbers. The valence electrons: the electrons in the highest (outer) main energy level (last energy level filled with electrons). Continuous spectrum: the spectrum that contains all the frequencies or all the colors of the visible light. Line spectrum: the spectrum that consists of a series of separate (discrete) lines that have specific colors (wavelengths/ frequencies) and that the lines become closer together (converge) towards the high energy end(the high frequency end / the shorter wavelength end / the violet end of the spectrum). ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter Three Periodicity: the repeating pattern of physical and chemical properties shown by the different periods and groups in the periodic table. The group number: the vertical columns in the periodic table which represent the number of valence electrons in the outermost shell. The period number: the horizontal rows in the periodic table which represent the number of occupied main energy levels in an element The atomic radius is defined as half the distance between the nuclei of two bonded atoms of the same element. Electronegativity: a measure of the ability of an atom to attract an electron pair or a bonding pair in a covalent bond. Ionization Energy: the minimum energy required to remove one electron from outermost shell of an isolated gaseous atom. X(g)® X+(g) + e- Volatility: the ability of a substance to escape or evaporate easily from a container. ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter Four: Ionic Bond: the electrostatic forces of attraction between oppositely charged ions which results from transfer of electrons. Covalent bond: electrostatic force of attraction between positively charged nuclei and shared electron pairs of electrons (bonding pairs) and it results from sharing of electrons between atoms. Dative covalent bond (coordinate covalent bond): the covalent bond in which both electrons are donated by one species or atom. Polar covalent bond indicates that bonding electrons are not equally distributed between the atoms in the bond (non–symmetrical distribution of electron cloud and ∆EN doesn’t = 0)) and that the more electronegative atom will have the greater electron density. This relatively small difference in charge is represented by partial positive and partial negative charges (δ+ and δ-). It is sometimes called dipole. Polar covalent molecule: the molecule in which one or more atoms is slightly negative and one atom or more is slightly positive that makes the bonds polarities don’t cancel each other (net dipole don’t = zero) Nonpolar covalent bond: the bond that indicates that bonding electrons are equally distributed between the two atoms (symmetrical distribution of electron cloud). The bond formed when the atoms in a molecule are alike and the bonding electrons are shared equally. (∆EN = 0) Non polar molecules: the electrons can at any moment be unevenly spread and a non symmetric charge distribution would exist within the molecule. This produces temporary instantaneous dipoles called Van der Waal's forces of attraction between molecules. Van der Waal's forces of attraction: An instantaneous (temporary) weak electrostatic attraction between the temporary induced dipoles. Dipole–dipole attractions a permanent intermolecular forces that arise from simple electrostatic attractions between molecular dipoles. It is found between polar molecules except those which have hydrogen bond. Hydrogen bond: a permanent intermolecular forces that arise from simple electrostatic attractions between molecular dipoles. It can be considered to be a relatively strong intermolecular force of attraction in which a hydrogen atom that is covalently bonded to a very electronegative atom (N, O or F) is also weakly bonded to an unshared pair of electrons of an electronegative atom. It is found between polar molecules Metallic bond is the electrostatic attraction between a sea of delocalized valence electrons and the positive metal ions (cations). ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter Five: Enthalpy change (∆H) is defined as [the enthalpy of products] – [enthalpy of reactants]. Standard enthalpy change (∆HӨ): is defined as [the enthalpy of products] – [enthalpy of reactants] at standard conditions - pressure = 1.01 × 102 KPa and temperature = 298 K. Exothermic Reaction: the reaction, in which energy is released to the surroundings; the products have a lower enthalpy (energy) than reactants. The reaction has a negative ∆H Endothermic reaction: the reaction, in which energy is absorbed from the surroundings; the products have a higher enthalpy (energy) than reactants. The reaction has positive ∆H. Heat: is a measure of the total energy in a given amount of substance and there fore it depends on the amount of substance present. Temperature: it represents the average kinetic energy of particles in the substance but it is independent of the amount of substance present The standard enthalpy change of combustion, ∆HӨc, is the enthalpy change when one mole of a substance is completely combusted in oxygen under standard conditions at 298 K (25 oC) and 1.01 X 102 KPa (1 atm pressure). Average bond enthalpy: is defined as the amount of energy required to break one mole of covalent bonds in the gaseous state or in a gaseous substance where average means that each value is the average of the enthalpies for a specific bond calculated from a range of similar compounds. ----------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter Six: The rate of a chemical reaction: the decrease in the concentration of a reactant per unit of time OR the increase in the concentration of a product per unit of time. Activation energy (Ea): is defined as the minimum energy required for a reaction to occur. Catalyst: is defined as substance that increases the rate of a chemical reaction without being chemically changed at the end of the reaction. ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 7 Dynamic Equilibrium: the reaction in which both reactants and products keep reacting and the reaction proceeds in both directions. Reversible reaction: the reaction which proceeds in both direction and never goes to completion. Once some products are formed the reverse reaction can take place to reform the reactants. Closed System: is the system in which neither matter nor energy can be lost or gained from the system, that is, the macroscopic properties remain constant. If the system is open some of the products from the reaction could escape and equilibrium would never be reached. Homogenous equilibrium: is the one in which all the reactants and the products are in the same phase or state. Heterogeneous equilibrium: is the one in which the reactants and the products are not in the same phase or state. Le Chatelier principle: If a system at equilibrium is disturbed, the equilibrium moves in the direction which tends to reduce the disturbance or the stress. ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 8: Bronsted–Lowry acid is defined as a proton (H+1) donor. Bronsted –Lowry base or an alkali is defined as a proton (H+1) acceptor. The conjugate base is the species (base) remaining after the acid has lost a proton. The conjugate acid is the species (acid) formed after the base has accepted a proton. Conjugate acid–base pair is defined as a pair that differs by a proton, H+1. Monoprotic acid is defined as an acid that contains one replaceable hydrogen atom per molecule. Diprotic acid: is defined as an acid that contains two replaceable hydrogen atoms per molecule. Triprotic acid: is defined as an acid that contains three replaceable hydrogen atoms per molecule. Polyprotic acid is defined as an acid that contains more than one replaceable hydrogen atom per molecule. Amphoteric substance: a substance that acts as an acid in one instant and as a base in another instant. Lewis acid is defined as an electron pair acceptor. Lewis base is defined as an electron pair donor. Dative covalent bond (coordinate covalent bond): the covalent bond in which both electrons are provided by one species. Alkalis: the bases which are soluble in water. The pH is defined as pH = – log10 [H3O+1] or minus the logarithm to the base ten of the hydrogen ion concentration. Strong acid is defined as an acid that ionizes or dissociates completely in water. It is called a strong electrolyte. Its complete ionization produces a lot of H3O+1 ions. Weak acid is defined as an acid that ionizes or dissociates partially in water. It is called a weak electrolyte. Its partial ionization produces a small concentration of H3O+1 ions. Strong alkali is defined as an alkali that ionizes or dissociates completely in water. It is called a strong electrolyte. Its complete ionization produces a lot of OH-1 ions. Weak alkali is defined as an alkali that ionizes or dissociates partially in water. It is called a weak electrolyte. Its partial ionization produces a small concentration of OH-1 ions. ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 9 Definition of oxidation and reduction in terms of electron(s) transfer: Oxidation: the loss of electrons. Reduction: the gain of electrons. Definition of oxidation and reduction in terms of oxidation number: Oxidation: the increase in the oxidation number. Reduction: the decrease in the oxidation number. Redox reaction is defined as a chemical reaction in which one substance is oxidized and at the same time another substance is reduced. Reducing agent is defined as the species that loses electrons (oxidized). Oxidizing agent is defined as the species that gains electrons (reduced). ----------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------- Chapter 10 Structural formula shows the bonding between atoms in the molecule (shows unambiguously how the atoms are arranged together. Full structural formula (sometimes called a graphic formula or displayed formula) shows every atom and bond. Condensed structural formula can omit bonds between atoms and can show identical groups bracketed together, Functional group is defined as an atom or a group of atoms responsible for the characteristic reactions of the molecule or the homologous series. Homologous series is defined as a group of organic compounds or as a series of organic chemicals with same general formula where neighboring members differ by CH2 unit. Alkanes are saturated hydrocarbons in which all the bonds between carbon atoms are single bonds. Alkenes are unsaturated hydrocarbons characterized by the presence of at least one carbon – carbon double bond. Primary alcohols: R-CH2-OH: the alcohol in which the carbon atom that is directly bonded to the functional group OH is surrounded by one alkyl group and two H atoms. Secondary alcohols: R2-CH-OH: the alcohol in which the carbon atom that is directly bonded to the functional group OH is surrounded by two alkyl groups and one H atom. Tertiary alcohols: R3-C-OH: The C atom that is directly bonded to the functional group OH is surrounded by three alkyl groups and no H atoms. Primary halogenoalkanes: R-CH2-X: The halogenoalkane in which the carbon atom that is directly bonded to the functional group X is surrounded by one alkyl group and two H atoms. Secondary halogenoalkanes: R2-CH-X: The halogenoalkane in which the carbon atom that is directly bonded to the functional group X is surrounded by two alkyl groups and one H atom. Tertiary halogenoalkanes: R3-C-X: The halogenoalkane in which the carbon atom that is directly bonded to the functional group X is surrounded by three alkyl groups and no H atoms. Isomers (Isomerism): are molecules with the same molecular formula but they have different structural formulas. They differ in the sequence in which the atoms are joined together. Structural isomers: molecules with the same molecular formula but they have different structural formulas and they belong to the same homologous series. Functional group isomers: molecules with the same molecular formula but they have different structural formulas but they belong to different homologous series. Substitution: is defined as replacement of one atom or group in a molecule by another. In this reaction one hydrogen atom is replaced by one halogen atom. Homolytic fission is defined as breaking of a covalent bond to give two fragments with an electron each or bond breaking in which each product takes one electron from the bond. The products from homolytic fission are called free radicals. Free radical is defined as a species with an unpaired (single) electron. They are highly reactive. Examples of free radicals: Cl•, Br• , CH3• and C2H5•. Heterolytic fission is defined as breaking of a covalent bond in a way so that the more electronegative atom of the two atoms joined by the bond takes both of the electrons to form an anion and the less electronegative atom forms a cation. Addition reaction: the reaction in which the double bond of an alkene is broken down. Addition across a double bond occurs at both C atoms. Bromine Test (Bromination): The usual test for the presence of a double bond is to add bromine water to the compound. If a double bond is present, the bromine water changes color from orange to colorless. Bromination can be used to distinguish between alkanes and alkenes. Alkenes react with bromine water and decolorize it (changes color from orange to colorless) while alkanes have no effect on the color of bromine water. Polymers: are defined as long chain molecules that are formed by the joining together of a large number of small molecules called monomers. Polymers are usually referred to as plastics. Nucleophile is a reagent that is neutral or negatively charged that has non – bonding pair of electrons. Typical nucleophiles are OH-1, CN-1 and NH3. Nucleophilic substitution reaction is defined as replacement of an atom or group in a molecule by a species with a lone pair of electrons. In these reactions nucleophiles act as Lewis bases, because they donate a pair of electrons. To show the movement of a pair of electrons, Addition polymerization: is defined as a process in which unsaturated monomers combine to form a polymer without the elimination of any atoms or molecules. In this type of polymerization the monomers contain double bonds and in the addition reaction the double bonds are replaced with single bonds between the monomers. This means that the structural feature needed in the monomer is the presence of a carbon – carbon double bond. SN1 stands for: S: substitution N: Nucleophilic 1: unimolecular slow step SN2 stands for: S: substitution N: Nucleophilic 2: bimolecular slow step
  7. Once I got so drunk, i thought the tree was my friend, i started doing karate moves and tripped, everyone was laughing! it was a badass tree btw
  8. Hey, my chemistry teacher has been teaching this syllabus since 2001, he told me there are 4 main things when it comes to officials Definitions Graphs Formulas (These account for almost 60% of the grade) Explanations account for 40% so my biggest tip is, to study the main definitions, i will attach them, my teacher sent ALL the definitions you need to know for SL and HL study the graphs ( unit 1 & in kinetics SL + HL and in Acids and Bases) Learn how to solve equations [ this will help you mostly in unit 1, energetics, kinetics, equilibrium, acids and bases, and redox) the rest are bonding and organic, you will need to MEMORIZE them this will only take about 4 hours tomorrow, since tmw is your last day hope this was helpful
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