Strong intermolecular forces high viscosity if you

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Strong intermolecular forces High viscosity
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If you increase a liquid’s temperature, you decrease its viscosity. If you decrease a liquid’s temperature, you increase its viscosity. (“Slower than molasses in winter”) Molecular shape also influences viscosity: Longer, linear molecules have more surface area, so more IMF, so higher viscosity. Shorter, nonlinear molecules have less surface area, less IMF, and lower viscosity.
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The Uniqueness of Water Why? 1) large ΔEN between H and O, and 2) two lone pairs on O This results in a bent and VERY polar molecule, allowing for FOUR H-bonds with neighboring molecules! 1) Solvent properties : due to polarity and H-bonding capability (“Universal Solvent”) Dissolves ionic compounds via ion-dipole IMF Dissolves many polar covalent compounds (e.g., ethanol, glucose, NH 3 ) via H-bonding Dissolves many nonpolar covalent gases (O 2 , CO 2 , to limited degrees) via dipole-induced dipole and dispersion forces
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1) Thermal Properties : very high heat capacity and heat of vaporization (again, due to H-bonding IMF) High heat capacity beneficial to aquatic life (limits temperature fluctuations) and terrestrial life (water in atmosphere also limits temperature fluctuations) High heat of vaporization is also essential for our survival: Average adult human has about 40 kg of body water and generates about 10,000 kJ of heat each day from metabolism; if this heat were used only to increase the average KE of body water, the temperature increase would mean immediate death; however, due to water’s H-bonds, the energy is converted to PE as it breaks the H-bonds and evaporates sweat, resulting in stable body temperature and minimal loss of body fluid.
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3) Surface Properties : high surface tension and capillarity vital for land plants’ ability to draw water from the ground, and for surface aquatic life via plant debris resting on pond surface, thereby providing shelter and nutrients, etc. 4) Density of Solid and Liquid Water : H-bonds (four per molecule of water) yield a hexagonal open structure in ice (snowflakes), with large spaces within the ice that give the solid state of water a lower density (and greater volume) than the liquid state of water; this is beneficial to aquatic life because frozen water forms from the top of a lake down, and not from the bottom up
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Maximum Density 4 0 C Ice is less dense than water Density of Water Water is a Unique Substance
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A crystalline solid possesses rigid and long-range order. In a crystalline solid, atoms, molecules or ions occupy specific (predictable) positions. An amorphous solid does not possess a well-defined arrangement and long-range molecular order. A unit cell is the basic repeating structural unit of a crystalline solid. Unit Cell lattice point Unit cells in 3 dimensions At lattice points: Atoms Molecules Ions
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Coordination Number = 6 (4 in each particle’s own layer, plus one above and one below) Diamond-Shaped Spaces between particles Packing Efficiency = 52% (not common)
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Coordination Number = 8 (4 above and 4 below) Layers a-b-a-b-a-b, etc.
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