LIQUIDS Flashcards
Targets of the lesson
★ explain and compare properties of liquids and solids;
★ differentiate intermolecular forces and intramolecular forces
★ enumerate & describe the types of intermolecular forces of attraction;
★ predict the intermolecular forces possible for a molecule;
★ rank molecules according to strength of intermolecular forces;
★ describe the following properties of liquids, and explain the effect of intermolecular forces on these properties: Viscosity, Surface Tension, Capillarity, Evaporation, Boiling point, and Vapor Pressure
Condensed Matter
Consists of solids and liquids, characterized by strong intermolecular forces, maintaining local order
Gaseous Substances
Relatively few in the Periodic Table
Water’s transition from solid to liquid to gas
The molecules remain intact
Changes in states
due to changes in the forces
among the molecules
Intramolecular Forces
involve covalent or ionic bonding (occur within molecule)
Intermolecular Forces
involve weaker interactions (occur between molecules)
Interparticle Forces
forces in ionic and metallic substances
Types of Intermolecular Forces
Dipole-dipole, Hydrogen Bonds, van der Waals’ or London Dispersion
Dipole-dipole
Dipoles weaken as distance between them increases, and are less significant at low pressures in the gas phase where molecules are dispersed; balance attraction and repulsion by orienting molecules to maximize B,E interactions and minimize B,B, and E,E interactions; permanent = polar
Hydrogen Bonds
polar w/ H & F/O/N/S; Particularly strong dipole–dipole forces; The strength of these interactions is due to the large EN diff of the bond and the close approach of dipoles due to the small size of the H atom; has a very important effect on physical properties: boiling points, due to the large hydrogen bonding interactions found in the smallest molecules with the most polar X-H bonds.
van der Waals’ or London Dispersion
forces that exist among noble gas atoms and
nonpolar molecules; present in all molecules, with stronger dipole-dipole interactions observed in polar molecules; weak and short-lived interatomic attraction, a phenomenon that can be significant, especially for large atoms.
Assumption that an atom’s electron are uniformly distributed around the nucleus (van der Waals’)
not always accurate
instantaneous
dipole that occurs accidentally in a given (van der Waals’)
can then induce a similar dipole in a neighboring atom even in nonpolar
molecules
A momentary nonsymmetrical electron distribution
can create a temporary dipolar charge arrangement, affecting neighbouring atoms’ electron distribution.
The Liquid State
Vital to our lives; have low compressibility, lack of rigidity, and high density compared to gases, providing insight into their nature.
Properties of Liquid
Viscosity, Cohesive and Adhesive Forces, Surface Tension, and Capillary Action
Viscosity
measures a liquid’s resistance to flow, influenced by factors such as IMF strength, molecule size/shape, and temperature. Larger IMFs are highly viscous.
Cohesive
minimize surface of liquid molecules, while adhesive forces between liquid molecules and container shape the meniscus. Water’s adhesive forces are stronger than cohesive forces.
Adhesive
container > its cohesive forces = concave shape of the meniscus, else convex shape water’s adhesive forces toward the glass are stronger than its cohesive forces (“wet surface”)
Capillary Action
adhesive + cohesive force > gravity; spontaneous rising of a liquid in a narrow glass tube is due to cohesive and adhesive force, while the liquid flows through the material due to attraction.
Surface Tension
The resistance of a liquid to surface area increase depends on the strength of cohesive forces, with water having irregularly high surface tension due to strong H bonds and size; A liquid molecule attracts surrounding molecules, while a surface molecule is only attracted by molecules below it and on each side.
Vaporization
occurs when molecules of a liquid escape the surface and form a gas.
heat/enthalpy of vaporization (Δ/Hvap)
the energy required to evaporate one mole of a liquid at a pressure of 1 atm.
Large IMF liquids
have low vapor pressures due to molecules needing high energies to escape to the vapor phase.
Solids have vapor pressures similar to-
liquids, and sublimation directly transitions from the solid to the gaseous state without passing through the liquid state; Vapor pressure increases significantly with Temperature
Strongest IMF type (formal changers)
Ion-ion
Second strongest IMF type (formal charge and partial charge)
Ion-dipole
Third strongest IMF type ( partial charge)
Dipole-dipole
Special type of Dipole-dipole
Hydrogen-bond
Weakest IMF type (induced dipoles)
van der Waals’ or London Dispersion
The stronger the IMF, the more ______ is needed to -
the more heat energy is needed to pull the molecules apart and put it in the gas phase, so it boils at high temperature
Uniqueness of Water
Thermal Properties, Great Solvent Power, Surface Property, and Unusual Density of Solid Water
Great Solvent Power of Water
Dissolves polar nonionic subs; Ion-dipole forces are used to dissolve ionic compounds, separating them from solids and maintaining their presence in solution; The induced dipole and dispersion force play a crucial role in the limited extent to which nonpolar atmospheric gases dissolve.
Thermal Properties of Water
Specific heat capacity, Heat of vaporization
Surface Property of Water
High surface tension, High capillarity
Unusual Density of Solid Water
The large spaces within ice makes the solid less dense than the liquid; At 0°C, ice melts due to the closer packing of loosened molecules, resulting in a more dense liquid water structure; The tetrahedral arrangement of H-bonded water molecules results in a hexagonal, open structure of ice.
