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Liquids and Intermolecular Forces. Surface tension Adhesive forces Cohesive forces Viscosity. Some Properties of a Liquid. Adhesion: forces between liquid molecules and their container Cohesion: intermolecular forces between molecules. Adhesive and Cohesive Forces.
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Liquids and Intermolecular Forces • Surface tension • Adhesive forces • Cohesive forces • Viscosity
Some Properties of a Liquid Adhesion: forces between liquid molecules and their container Cohesion: intermolecular forces between molecules
Adhesive and Cohesive Forces What can be said about the adhesive forces (glass and liquid) and the cohesive forces (between molecules of liquid)? Liquid wets this surface easily because the adhesive forces are _______er than thecohesive forces.
Meniscus Formation Comment on adhesive and cohesive forces in each tube.
Some Properties of a Liquid Surface Tension: A substances resistance to an increase in its surface area
Surface Tension To create more surface, the molecules at the surface must be separated from one another. To separate the molecules requires that work be done. Surface tension must be overcome.
Some Properties of a Liquid Capillary Action: Spontaneous rising of a liquid in a narrow tube.
Capillary Action Liquid rises in the glass tube because adhesive forces overcome the force of gravity.
Some Properties of a Liquid Viscosity: Resistance to flow
Comparing Viscosity Which of the two liquids has stronger intermolecular interactions? How can you tell?
Stronger force increases: surface tension, viscosity, boiling point, adhesion, cohesion • For similar size molecules: Strongest → weakest Hydrogen bonds → dipole → London dispersion • For London Dispersion forces: Strongest → weakest More electrons → less electrons
Stronger force increases: surface tension, viscosity, boiling point, adhesion, cohesion • For dipole forces: Strongest → weakest More polar → less polar • For hydrogen bonding: More sites for hydrogen bonds (more electron pairs on the electronegative atom) increases surface tension, viscosity, boiling point, adhesion, cohesion