NU CHEM 1214 - Chapter 10: Interparticle Forces, Liquids, and Solids

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General Chemistry 2 (CHEM 1214): Final Exam Preparation GuideChapter 10: Interparticle Forces, Liquids, and Solids !polarity = presence of separation, a lack of unity polar-covalent bond = asymmetric electron distribution in a covalent bond, where a moderately high different (0 - 2) in electronegativity exists electronegativity (EN) = tendency of an element to attract other electrons through polar-covalent bonds - the side with greater electronegativity has more electrons - the side with lesser electronegativity has fewer electrons • polarity is represented using a dipole arrow • electronegativity is predictable on a Periodic table, with the most electronegative elements being on the upper right-hand corner of the table bond type: determined by difference in electronegativity (∆EN) •∆EN is greater than 2: ionic bond •∆EN is between 0.01 and 2: polar covalent bond •∆EN is 0: non-polar covalent bond !how to determine polarity in a molecule: -draw a correct VSEPR structure -identify the electronegative atoms -draw the appropriate dipole arrow → if the arrows are pointing in the same direction, then the molecular is polar dipole moment (µ) = the product of the change in magnitude (Q, in Coulombs) and the distance between the atoms themselves (d, in meters) - molecules which are polar will display this property !intramolecular forces = attractions which hold atoms together (in a molecule) •ionic bonding: between a cation and anion; no electron sharing, attraction is electronegative •polar covalent bonding: unequal sharing of electrons •non-polar covalent bonding: equal sharing of electrons, electronegativity is zero → allow separate particles to congregate, as molecules with similar properties will tend to stick together !polarizability = the ability to distort an electron cloud → the electron cloud is comparable to clay and is moldable; polarizability results in the development of a change in separation across a non-polar particle !intermolecular forces = forces which hold molecules together •ion-dipole: an ion charge and a dipole charge - between an anion or cation and the pole of molecule with the opposite charge (Cl⁻ and H2O, or Na⁺ and H2O) •dipole-dipole: two dipoles charges - between two oppositely charged particle poles of two separate polar molecules •H-bond: a strong type of dipole-dipole interaction - a polar-covalent bond between a hydrogen and a dipole charge of a negatively-charged particle pole (exclusively F, O, N particle) note: polar bonds in a molecule does not dictate the polarity of a molecule - this is determined a dipole arrow onlypolar molecule polar molecule non-polar moleculeµ = QdGeneral Chemistry 2 (CHEM 1214): Final Exam Preparation Guide•induced dipole: between a cation or anion and an otherwise non polar molecule which has turned into a dipole through an electron cloud distortion •ion-induced dipole: between a polar molecule and an otherwise non-polar molecule which has turned into a dipole through an electron cloud distortion •dispersion forces (London): results from an electron cloud distortion in a particle, which forms polarization between two otherwise non-polar molecules - all matter possesses this force, regardless of charge or polarity - dispersion forces increase when molar mass and electron cloud size increases → most powerful force → ion-dipole → H-bonding → dipole-dipole → ion induced dipole → induced dipole → dispersion forces → least powerful force !physical properties = vapor pressure, boiling/freezing point, surface tension, viscosity → the stronger an intermolecular force, the lower the vapor pressure, the higher the boiling point, the higher the surface tension, and the higher the viscosity vapor pressure = pressure of a liquid in equilibrium with its vapor → intermolecular forces directly influence vapor pressure, since more escape energy is required to liberate vapor from the liquid phase with strong intermolecular forces present dynamic equilibrium = occurs when the rate of vaporization equals the rate of condensation (where a constant temperature is established) solubility → polar solvents, which have large polar charges, can dissolve solutes with charge character (such as salts and polar molecules) → non-polar solvents dissolve solutes which lack a charged character (non-polar molecules) • like dissolves like - similar solutes will dissolve in similar solvents viscosity = resistance to flow in a liquid; more viscous liquids will flow with less facility surface tension = energy required to increase the surface area by a given amount capillarity = a liquid’s ability to climb up a thin tube, only when adhesive forces are stronger than cohesive forces will a liquid climb up a tube • cohesive forces: attractive forces between molecules • adhesive forces: attractive forces between a molecule and a surface (of a tube, for example) physical changes = condensation, vaporization, fusion (melting), freezing, deposition, sublimation → heat flow occurs during physical changes → highest temperature to lowest temperature: gas → liquid → solid → temperature changes can occur within a phase, but NOT during a transition from one phase to another (for example, the transition from solid to liquid in H2O will ALWAYS be at 0ºC) - this occurs because energy will be completely dedicated to breaking intermolecular bonds, and cannot enter the surroundings !phase diagrams: • gas prefers high temperature and low pressure •solid prefers low temperature and high pressure •liquid prefers an intermediary between the two !•triple point = where all three phases exist in equilibrium •critical point = where liquid and vapor are indistinguishable •supercritical point = phase present beyond critical point → H2O has a solid state less dense than its liquid state, which generates a negative slope in the diagramGeneral Chemistry 2 (CHEM 1214): Final Exam Preparation GuideChapter 11: Colligative Properties of Solutions !mixture = a combination of two ore more pure substances •heterogenous mixtures: not uniformly mixed •homogenous mixtures: uniformly mixed → also known as a solution - in a solution, there is a solute (dissolved material, and what is being diluted) and a solvent (medium into which the solute is dissolved, the environment) colloid = a mixture where the

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NU CHEM 1214 - Chapter 10: Interparticle Forces, Liquids, and Solids

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