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ChemSemis

Terms in this set (73)

Kinetic Molecular Model
- explains the properties of solids and liquids in terms of the molecular forces of attraction and the kinetic energy of the individual particles.
Intermolecular Forces
- (attractive forces between neighbouring particles of one or more substances) pull the particles together.
Kinetic Energy
- keeps particles at a distance and/or moving around. It is dependent on the temperature of the substance.
Solids
____ assume a crystalline structure when they have a highly ordered packing arrangement.
Formula Units
- particles of an ionic compound
Covalent Compounds
- may only exist as liquids due to relatively weaker intermolecular forces.
Van der Waals forces
- all intermolecular forces of attraction in a pure substance.
Dipole-dipole
- exists between polar molecules.
Polar substances
- are those that possess a permanent dipole moment attributed to the difference in electronegativities of their component atoms and how these atoms are arranged in space.
nonpolar
x<0.4
polar
0.4-1.8
ionic
x>1.8
Hydrogen bonds
- a special type of dipole-dipole interaction that exists only in molecules that contain hydrogen atom bonded to a small, highly electronegative atom such as N, O or F
Hydrogen bonds
- is about five to ten times stronger than other dipole-dipole attractions.
Hydrogen bonds
- is not a real chemical bond participated in by electrons. It is intermolecular in nature
Covalent bonds
- electrons are involved and shared between atoms. It is a type of intermolecular force of attraction.
Ion-dipole
- acts between an ion (either positive or negative) and a polar molecule
Ion-dipole
- becomes stronger either as the charge of the ion increases, or as the magnitude of the dipole moment of the polar molecule increases
degree of ion-dipole interaction
The ____ depends on the size and charge of the ion and on the size and dipole moment of the polar molecule.
London dispersion
- or simply dispersion forces, are intermolecular forces of attraction that exist between all atoms and molecules.
London dispersion
- the only forces acting in nonpolar molecules.
Nonpolar Molecules
- have zero dipole moment because their electron density is uniform and symmetrical.
Temporary dipole
- or instantaneous dipole, induce dipoles in neighbouring molecules
size of a molecule
The ____ can affect the London dispersion force between two molecules. The bigger the molecule the stronger the attraction between two molecules.
Surface Tension
- property of a liquid to resist an external force and thus assume a lesser surface area
Viscosity
- the resistance of a liquid to flow. Thickness or thinness of water
viscous
The greater the intermolecular forces, the more ___ the substance
Vapor Pressure
- pressure exerted by its vapor when in equilibrium with its liquid or solid.
Boiling Point
- is the temperature at which its vapor pressure is equal to the external or atmospheric pressure
Normal Boiling Point
- the temperature at which a liquid boils under an atmospheric pressure of 760mm Hg
boiling point
The ___ of a liquid is influenced by the strength of its intermolecular forces. The greater the attractive forces, the higher the energy needed to increase the kinetic energy of the molecules to break these forces
Molar Heat of vaporization
- the amount of heat required to vaporize one mole od a substance at its boiling point.
Molar Heat of vaporization
- is determined by the strength of the intermolecular forces between molecules.
Crystalline solids
- solid that have a highly regular arrangement of particles
Amorphous solids
- solids that have considerable disorder in their structure
Amorphous solids
- are formed rather rapidly that its constituent particles do not have time to align or organize into a more definite crystalline lattice.
Lattice
- is a three-dimensional system of points designating the positions of the components (atoms, ions or molecules) that make up a crystal
Unit Cell
- the smallest repeating unit of a lattice.
Ionic solid
- ions are held together by strong coulombic forces
Molecular Solid
- has discrete covalently bonded molecules at each of its lattice points
Metallic Solid
- are composed of metal atoms bonded together by metallic bonds
Network Solid
- are covalently bonded atoms that form a continuous network.
Group 8A solid
- consists of atoms of noble gases held together by London dispersion forces
Phase Changes
- occur with increased temperature
Sublimation
- process in which solid into vapor
Phase diagrams
- is a graphical representation of the pressure-temperature relationships that apply to the equilibria between the phases of a substance
Phase diagrams
- useful in determining the combination of temperature and pressure at which substance will exist as solid, liquid or gas, or the conditions at which two phases exist in equilibrium.
Triple point
- is where all the three phases coexist in equilibrium
Critical point
- the temperature-pressure condition at and above which the vapor of the substance cannot be liquefied no matter how much pressure is applied.
Supercritical fluid
- is a substance that has temperature above its critical temperature and a density near its liquid density
Solutions
- are mixture of two or more substance evenly distributed throughout a single phase
Solute
- the substance dissolved in a solution, usually present in smaller amount.
Solvent
- is the dissolving medium.
Unsaturated sol.
- a solution that contains less solute than the solvent's capacity to dissolve.
Saturated sol.
- contains the maximum amount of solute that the solvent can dissolve at a certain temperature.
Supersaturated
- contains more dissolved solute than is present in a saturated solution. This type of solution is unstable
polarity
For two substances to form a solution, they must have the same nature in terms of ___
(expanding the solvent - endothermic)
Overcoming the intermolecular forces in the solvent to give room for the solute.
(expanding the solute - exothermic)
Separating the solute into its individual components
(enthalpy)
Allowing the solute and the solvent to interact to form the solution
Enthalpy of solution
- is the enthalpy change associated with the formation of the solution
Concentration
- is a measure of the amount of solute in a given amount of solvent or solution
Mole fraction
- a component in a solution that is equal to the number of moles of that component divided by the total number of moles of all the components present.
Molality
- the number of moles of solute per kilogram of solvent
Molarity
- the number of moles of solute per liter of solution
Parts per million
- the number of parts of solute per one million parts of the solution
Solubility
- is the maximum amount of a solute that can dissolve in a given amount of solvent at a specific temperature
True
Ionic and polar solutes are soluble in polar solvents. While nonpolar solutes are soluble in nonpolar solvents.
Colligative properties
- properties that depend solely on the number of solute particles in a solution. Include vapor pressure lowering, freezing point depression, boiling point elevation and osmotic pressure. Are influenced by the extent of dissociation of the solute in a solution.
electrolytic or nonelectrolytic
Solutions that depend on the nature of their components can be classified as ___ or ___.
Electrolytes
- are particles that ionize in a solution, as a result, they conduct electricity
Nonelectrolytes
- are those that do not ionize at all in a solution and thus not conduct electricity
Raoult's Law
- states that vapor pressure of a solvent over a solution is equal to the product of the vapor pressure of the pure solvent
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