differences in magnitudes of attractive forces due to differences in strengths of dipole-dipole attractions.1) comparable molecular weights and shapes = equal dispersion forces. comparing relative strengths of intermolecular attractions:.dispersion forces operate between all molecules.greater surface contact ® greater boiling point and London dispersion forces.Molecular shape affects intermolecular attractions.Dispersion forces increase in strength with increasing molecular weight.London dispersion forces increase with increasing molecular size.larger molecules have greater polarizability.greater polarizability ® more easily electron cloud can be distorted to give momentary dipole.polarizability – ease in which the charge distribution in a molecule can be distorted.molecules have to be very close together.motion of electrons can create an instantaneous dipole moment.interparticle forces that exist between nonpolar atoms or molecules.increase temperature forces molecules to be closer together ® increase in strength of intermolecular forces.condensed phases – liquids and solids because particles are close together compared to gases.interparticle attractions draw particles together.kinetic energies depends on temperature and tend to keep particles apart and moving.state of substance depends on balance between the kinetic energies of the particles and interparticle energies of attraction.Retains its own shape and volume Is virtually incompressible Diffusion within a solid occurs extremely slowly Does not flow crystalline – solids with highly ordered structuresĪssumes both the volume and shape of container is compressible diffusion within a gas occurs rapidly flows readilyĪssumes the shape of the portion of the container it occupies Does not expand to fill container Is virtually incompressible Diffusion within a liquid occurs slowly Flows readily.intermolecular forces hold molecules together and keep them from moving.attractive forces not strong enough to keep molecules from moving allowing liquids to hold shape of container.lack of strong attractive forces allows gases to expand.average kinetic energy of the molecules is larger than average energy of attractions between molecules.The kinetic energy keeps the molecules apart and moving around, and is a function of the temperature of the substance and the intermolecular forces try to draw the particles together. The state of a substance depends on the balance between the kinetic energy of the individual particles (molecules or atoms) and the intermolecular forces. \)ġ1.1: A Molecular Comparison of Gases, Liquids, and Solids
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