CHEM-002 Chapter Notes - Chapter 11: Intermolecular Force, Surface Tension, Viscosity

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Intermolecular Forces Chem 002: Phases
11.3 Properties of Liquids
Viscosity: resistance of liquid to flow (high viscosity is resistant to flow, low viscosity flows easily)
Dependent on attractive forces, shape, flexibility
o These determine entanglement
Increases with molecular weight
Decreases with increasing temperature: greater Kinetic Energy overcomes attractive
(intermolecular) forces
Surface Tension: there is an imbalance of attractive intermolecular forces at the surface of liquids
There is a net inward force from the molecules inside, acting on the molecules on the surface
This reduces the surface area
Molecules at the surface pack closer together
This is wh soe isects ca walk o wate
Capillary Action: cohesive forces bind similar molecules and adhesive forces bind substance to surface
This is how liquids rise up a narrow tube
There are adhesive forces coming from the walls of a tube that pull the liquid towards it
Increases the surface area of the liquid
Surface tension reduces the area
This causes the liquid to be pulled up the tube until gravity balances the adhesive and cohesive
forces
11.4 Phase Changes
Accompanied by energy changes
Highest Energy: Gas
Middle: Liquid
Lowest: Solid
Phase changes: endothermic processes
Sublimation solid to gas
Deposition gas to solid
Condensation gas to liquid
Vaporization liquid to gas
Fusion/Melting solid to liquid
Freezing liquid to solid
Heating Curves: temperature is constant for endothermic processes (straight lines of a heating curve)
because the added energy (from heat) is used to break intermolecular forces
Critical Temperature: the highest temperature in which a liquid can exist
Critical Pressure: the highest pressure required to bring liquefaction at critical temperature
Greater intermolecular forces = greater critical temperature or pressure
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Document Summary

Viscosity: resistance of liquid to flow (high viscosity is resistant to flow, low viscosity flows easily) Dependent on attractive forces, shape, flexibility: these determine entanglement. Decreases with increasing temperature: greater kinetic energy overcomes attractive (intermolecular) forces. Surface tension: there is an imbalance of attractive intermolecular forces at the surface of liquids. There is a net inward force from the molecules inside, acting on the molecules on the surface. Molecules at the surface pack closer together. This is wh(cid:455) so(cid:373)e i(cid:374)sects ca(cid:374) (cid:858)walk o(cid:374) wate(cid:396)(cid:859) Capillary action: cohesive forces bind similar molecules and adhesive forces bind substance to surface. This is how liquids rise up a narrow tube. There are adhesive forces coming from the walls of a tube that pull the liquid towards it. This causes the liquid to be pulled up the tube until gravity balances the adhesive and cohesive. Increases the surface area of the liquid forces.