Properties of Liquids PDF

# Surface Tension - the measure of the elastic force in the surface of a liquid # Surface Tension - disrupts the H-bonding at the surface of water - surfactants # Cohesive & Adhesive Forces ## Cohesive Forces - between the molecules in the liquid ## Adhesive Forces - between the molecules and t...

# Surface Tension - the measure of the elastic force in the surface of a liquid # Surface Tension - disrupts the H-bonding at the surface of water - surfactants # Cohesive & Adhesive Forces ## Cohesive Forces - between the molecules in the liquid ## Adhesive Forces - between the molecules and the surface of another substance ## Water - concave ## Mercury - convex # Capillary Action - rise of liquids up narrow tubes - which results from the competition between the cohesive forces and the adhesive forces - "capillarity" # Viscosity - the measure of a liquid's resistance to flowing - ↑ viscosity = ↓ speed - related to the intermolecular forces present - ↑ viscosity = stronger IMF = ↓ temperature - Unit: poise, P - Pa-s or N-s/m² ## Viscosities of a Series of Hydrocarbons at 20 °C | Substance | Formula | Viscosity (kg/m-s) | |---|---|---| | Hexane | CH3CH2CH2CH2CH2CH3 | 3.26 × 10-4 | | Heptane | CH3CH2CH2CH2CH2CH2CH3 | 4.09 × 10-4 | | Octane | CH3CH2CH2CH2CH2CH2CH2CH3 | 5.42 × 10-4 | | Nonane | CH3CH2CH2CH2CH2CH2CH2CH2CH3 | 7.11 × 10-4 | | Decane | CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 | 1.42 × 10-3 | # Viscosity | Liquids | Viscosity (in Ns/m²) at 20°C | |---|---| | Acetone (C3H6O) | 3.16 × 10-4 | | Benzene (C6H6) | 6.25 × 10-4 | | Carbon tetrachloride (CCl4) | 9.69 × 10-4 | | Diethyl ether (C2H5OC2H5) | 2.33 × 10-4 | | Ethanol (C2H5OH) | 1.20 × 10-3 | | Glycerol (C3H8O3) | 1.49 | | Mercury (Hg) | 1.55 × 10-3 | | Water (H2O) | 1.01 × 10-3 | # Viscosity CH2-OH CH-OH CH2-OH - Three-hydrogen bonding sites - Molecular shape # Vapor Pressure of Liquids - Open: some water molecules go out. - Closed: none of the gas particles are able to get out. # Vapor Pressure of Liquids - Number molecules that go into the gaseous state = number of molecules that condense back - rate of condensation = rate of evaporation of the liquid - the gas in the container is in EQUILIBRIUM with the liquid - no more net change occurs - Molecules still are changing but no net change - DYNAMIC EQUILIBRIUM - Vapor pressure is independent of volume of the container. # Equilibrium Vapor Pressure - pressure exerted by the gas in equilibrium with a liquid in a closed container at a given temperature - The molecules in the gaseous state over its liquid create a pressure. - ↑ number of gaseous particles, ↑ pressure - the maximum vapor pressure of a liquid at a given temperature # Vapor Pressure and Temperature - increases with temperature ## The Vapor Pressure of Water as a Function of Temperature | T (°C) | P (torr) | |---|---| | 0.0 | 4.579 | | 10.0 | 9.209 | | 20.0 | 17.535 | | 25.0 | 23.756 | | 30.0 | 31.824 | | 40.0 | 55.324 | | 60.0 | 149.4 | | 70.0 | 233.7 | | 90.0 | 525.8 | - Molecules have enough kinetic energy to overcome intermolecular forces # Vapor Pressure and IMF - liquids with high vapor pressure: - evaporate quickly - have weak IMF - liquids with low VP - strong London Dispersion Forces - strong dipole-dipole forces # Vapor Pressure and IMF | substance | vapor pressure at 25°C | |---|---| | Pentane | 0.71 atm - nonpolar | | Acetone | 0.28 atm - no H-bonding | | Ethyl alcohol | 0.08 atm - H-bonding | | Water | 0.03 atm - H-bonding | - The stronger the IMF are, the greater the amount of energy needed to break them. - The stronger the IMF are, the lower the pressure of a liquid is.