Intermolecular Forces and Properties of Solutions in Chemistry

Intermolecular Forces (IMF)

Attractive forces that molecules exert on one another, with strength related to the distance between particles.

Kinetic Energy (KEavg)

The average kinetic energy of molecules, which increases with temperature.

Ionic Bond

A bond formed when an atom donates electrons to another atom, typically between a nonmetal (anion) and a metal (cation).

Covalent Bond

A bond formed when two or more atoms share electrons, typically between nonmetals.

Metallic Bond

A bond formed between metal atoms, characterized by a sea of shared electrons.

Nonpolar Molecule

A molecule with an electronegativity difference of 0-0.4, where electrons are equally distributed.

Polar Molecule

A molecule with an electronegativity difference of 0.5-2.0, characterized by unequal distribution of electrons.

Dipole-dipole Interaction

An intermolecular force present in polar molecules.

Hydrogen Bonding (H-bond)

A strong intermolecular force present in polar molecules with hydrogen atoms bonded to fluorine, oxygen, or nitrogen.

London Dispersion Forces (LDF)

Weak intermolecular forces that exist in all molecules, more significant in nonpolar molecules.

Ion-ion Interaction

Interactions between ions in ionic compounds.

Ion-dipole Interaction

An interaction between ion/ionic compounds and polar molecules.

Induced-dipole Interaction

Occurs between nonpolar molecules and ions/polar molecules when a temporary dipole is induced.

Strength of IMF

The hierarchy of intermolecular forces from strongest to weakest: Ion-ion, Ion-dipole, H-Bonding, Dipole-dipole, LDF.

Viscosity

A measure of a fluid's resistance to flow; influenced by intermolecular forces and temperature.

Boiling Point

The temperature at which a liquid's vapor pressure equals the external pressure.

Melting Point

The temperature at which a solid becomes a liquid.

Vapor Pressure

The pressure exerted by a vapor in equilibrium with its liquid or solid form.

Stronger IMF

Results in higher boiling and melting points, and lower vapor pressure.

Weaker IMF

Results in lower boiling and melting points, and higher vapor pressure.

Viscosity

Measure of a fluid's resistance to flow; liquids that flow fast have lower viscosity and liquids that flow slow have higher viscosity.

Intermolecular Forces (IMFs)

Forces that help liquids take up space in a container and are directly related to surface tension, viscosity, and vapor pressure.

Surface Tension

The energy required to increase the surface area of a liquid; higher in liquids that have higher intermolecular forces.

Surfactants

Substances that reduce surface tension between liquids and solids.

Cohesion

The binding of like molecules.

Adhesion

The binding of a substance to a surface.

Meniscus

Curved surface of a liquid.

Vapor Pressure

Pressure exerted by vapor equilibrium with its liquid phase in a closed system.

Solubility

Ability of a substance to dissolve a given amount of solvent at a specified temperature.

Miscible Liquids

Liquids that are able to mix.

Immiscible Liquids

Liquids that are unable to mix.

Hydrophilic

Substances that can interact with water.

Hydrophobic

Substances that repel water.

Amphipathic Molecules

Molecules that have both hydrophilic and hydrophobic regions.

Properties of Water

Represented by the chemical formula H2O; known to be the universal solvent due to its capability to dissolve most substances.

Crystalline Solids

Solids arranged in a definite repeating pattern, held by a uniform strong IMF.

Amorphous Solids

Solids that lack the order found in crystalline solids and have structures at the atomic level similar to liquids.

Unit Cell

The small repeating unit in the structure of crystalline solids.

Crystal Lattice

The arrangement of geometrical patterns of points in a unit cell.

Motif

An atom or a group of atoms that is repeated at each lattice point to generate a crystal structure.

Metallic Solids

Solids that consist entirely of metal atoms, characterized by high electrical and thermal conductivity.

Heat Capacity

The amount of heat required to raise the temperature of a substance by 1°C.

Specific Heat Capacity

The amount of heat required to raise the temperature of 1g of a substance by 1°C.

Melting Point

The temperature at which a solid becomes a liquid; for water, it is 0°C.

Boiling Point

The temperature at which a liquid becomes a gas; for water, it is 100°C.

Covalent Network Solids

held together by covalent solids

Properties of Covalent Network Solids

poor conductors, high melting points, has allotropy, characterized by strength or hardness

Allotropy

the ability of a single element, atom, or molecule to form multiple structures of solids

Molecular Solids

made up of covalently bonded atoms that are held together by IMFs such as Van der Waals or weak dispersion forces

Properties of Molecular Solids

poor conductors (insulators), soft, high melting point, easily dissolve in water

Ionic Solids

composed of cations and anions that are held together by electrostatic attractions

Properties of Ionic Solids

difficult to break, high melting point, poor conductors, electrostatic attractions are stronger than Van der Waals

Melting Point

the temperature at which a solid loses definite shape and is converted to liquid

Freezing Point

the temperature at which a liquid changes to a solid

Heat of Fusion

the quantity of heat necessary to melt a solid

Sublimation

solid to gas

Deposition

gas to solid

Enthalpy of Sublimation

the quantity of heat to convert solid to vapor

Malleability

ability of a solid to undergo compressive stress without breaking it

Ductility

the ability of a solid to undergo tensile stress or stretched without fracture

Electrical Conductivity

the measurement of the ability of atoms, molecules, or ions to transfer electrons from one to another

Thermal Conductivity

the measurement of the ability of atoms, molecules, or ions to move and collide with its neighboring particles

Solid Solutions

homogeneous mixtures that appear as one phase, composed of solute particles dissolved in an appropriate solvent

Solute

substance being dissolved

Solvent

dissolving the substance

Unsaturated Solution

when the amount of solute is less than the solute's solubility at a given volume and temperature

Saturated Solution

when the amount of solute is equal to the solute's solubility at a given volume and temperature

Solubility

the ability of a solid, liquid, or gaseous chemical substance to dissolve in a solvent and form a solution.

Supersaturated Solution

when the amount of solute is greater than the solute's solubility at a given volume and temperature

Nature of Solute and Solvent

"like dissolves like" - solute and solvent molecules with the same IMFs are soluble to one another

Temperature

the most evident factor that affects solubility; most solids are soluble at higher temperatures; solubility of gases decreases as temperature increases.

Concentrated Solution

when a solution contains an excessively large amount of solute; molarities > 1M

Diluted Solution

solution of low concentration; molarities < 1M; prepared through the process of dilution

Percentage by Mass (%m/m)

𝑚=𝑚𝑎𝑠𝑠 𝑠𝑜𝑙𝑢𝑡𝑒/𝑚𝑎𝑠𝑠 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛× 100

Percentage by Volume (%v/v)

% 𝑚=𝑣𝑜𝑙𝑢𝑚𝑒 𝑠𝑜𝑙𝑢𝑡𝑒/𝑣𝑜𝑙𝑢𝑚𝑒 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛× 100

Percentage by Mass/Volume (%m/v)

% 𝑚=𝑚𝑎𝑠𝑠 𝑠𝑜𝑙𝑢𝑡𝑒/𝑣𝑜𝑙𝑢𝑚𝑒 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛× 100

Pressure or Volume

does not significantly affect the solubility of solids and liquids but greatly affects the solubility of gases; the greater the pressure the greater the gas dissolves in a solution

Henry's Law

the relationship between pressure of the gas over the solution and solubility of the gas; 𝑐𝑔𝑎𝑠=𝑘𝐻𝑃

Concentration of gas (M)

𝑐𝑔𝑎𝑠

Pressure of gas (atm)

𝑃

Henry's constant (M/atm)

𝑘𝐻

mass solution

mass solvent + mass solute

volume solution

volume solvent + volume solute

mole solution

mole solvent + mole solute

%volume

proof no. / 2

density

mass/volume

Molarity (M)

M= mol solute / L solution

Molality (m)

m= mol solute / kg solvent

Mole (n or mol)

n = mass (m) / molar mass (M)

Mole Fraction (𝜓)

𝜓= mol solute or mol solvent / mol solution

Parts per Million (ppm)

ppm= mass solute / mass solution × 10^9

Parts per Billion (ppb)

ppb= mass solute / mass solution × 10^12

Raoult's Law

The vapor pressure of an ideal solution (P) is the product of the pure solvent (Po) and the mole fraction of the solvent (XB) in the solution at the given temperature.

Colligative Properties

Properties of solutions that are dependent on the concentration of solute particles and not on the nature or mass of solute.

ΔP

ΔP = vapor pressure lowering

Boiling Point Elevation

The addition of solute in a solvent results in increased boiling point.

Boiling Point Elevation Formula

Tb = To + ΔTb

ΔTb

ΔTb = m * kb

Vapor-Pressure Lowering

Depends on the number of solute particles that have been added in the solution.

Volatile Substance

A substance that evaporates quickly and exhibits vapor pressure.