liquids_solids_15dec2017_3rd.notebook December 15, 2017

Properties of liquids • VISCOSITY – a measure of a liquid’s resistance to flow • Liquids with large intermolecular forces tend to be highly viscous • Molecules with high complexity are more viscous because they can become entangled with each other • Or long and stringy molecules • The more viscosity – the slower they move liquids_solids_15dec2017_3rd.notebook December 15, 2017

Properties of liquids

SURFACE TENSION Resistance of a liquid to an increase in its surface area Molecules in the center of a liquid are attracted by all atoms around them Molecules on the surface are attracted only by molecules below and on the sides Uneven pull tends to draw the molecule inward and causes drops to form, providing the lowest surface area liquids_solids_15dec2017_3rd.notebook December 15, 2017

Properties of liquids Capillary action Spontaneous rising of a liquid in a narrow tube Forces responsible: Cohesive forces – intermolecular forces among the molecules of the liquid Adhesive forces – forces between the liquid molecules and their container Polar substances – concave meniscus; the glass is polar and has a greater pull on the molecules than the cohesive forces (water) Nonpolar substances – convex meniscus; the cohesive forces are stronger than the adhesive forces (mercury) liquids_solids_15dec2017_3rd.notebook December 15, 2017

Properties of liquids Vapor pressure - Pressure of a vapor above a liquid in a closed container when the vapor is at equilibrium with the liquid Equilibrium of vapor pressure: rate of condensation of vapor = rate of evaporation of liquid The molecules are constantly moving back and forth from the liquid state to the vapor state, but there is no net change in the amount of vapor or liquid Volatile liquids – liquids with high vapor pressures that evaporate rapidly from an open container Lower intermolecular forces = greater volatility Low intermolecular forces in a liquid allow the molecules to escape easily from the liquid surface. The liquids have a high vapor pressure and a low boiling point Vapor pressure increases significantly with an increase in temperature due to an increase in the kinetic energy of the particles

Which compound do you think is more volatile: CCl4 or CBr4? Why?