Intermolecular_Forces__Liquids_and_Solids

Intramolecular forces

Attractive forces within molecules that create bonds and are responsible for chemical properties. Intramolecular forces are the attractive forces within molecules that we call “bonds.” They are responsible for chemical properties. These forces include ionic, covalent, and metallic bonds, which determine the structure and stability of compounds.

Intermolecular forces (IMFs)

Forces that exist between molecules, responsible for physical properties of substances. They include hydrogen bonds, dipole-dipole interactions, and London dispersion forces, influencing boiling and melting points.

Melting Point (MP)

The temperature at which a solid forms a liquid.

Boiling Point (BP)

The temperature at which a liquid forms a gas.

Ion-dipole forces

Forces that occur between an ion and a polar molecule. For example, when sodium chloride (NaCl) dissolves in water, the sodium ions (Na+) interact with the polar water molecules, causing the water molecules to orient themselves around the ions.

Dipole-dipole forces

Attractive forces that occur between neutral polar molecules, leading to interactions that affect physical properties. For example, in hydrogen chloride (HCl), the positive end of one molecule is attracted to the negative end of another, resulting in dipole-dipole interactions. When two polar molecules are near each other, dipole-dipole forces can develop.

London dispersion forces

Result from attractions between nonpolar molecules that form temporary dipoles; weakest of the IMFs. They increase with molecular size and mass.

Hydrogen bonding

A strong type of dipole-dipole force occurring only between hydrogen and highly electronegative atoms (F, O, N).

Polarizability

The ability of a dipole to be induced in nonpolar species; increases with mass.It refers to how easily the electron cloud of a molecule can be distorted to form temporary dipoles, influencing the strength of London dispersion forces.

Viscosity

The resistance of a liquid to flow; increases with molar mass.

Surface tension

The energy required to increase the surface area of a liquid, caused by imbalances of IMFs.

Cohesion

IMFs that bind similar molecules to one another.

Adhesion

IMFs that bind different substances together.

Volatility

The tendency of a substance to vaporize.

Critical temperature

The highest temperature at which a liquid can exist; above this, the substance can only be a gas.

Critical pressure

The pressure required to liquefy a substance at its critical temperature.

Phase diagram

A graph representing the equilibria between the solid, liquid, and gas phases of a substance.

Polar molecules

Molecules characterized by an unequal distribution of electrical charge, resulting in a dipole moment, which means they have a positively charged end and a negatively charged end.

Nonpolar molecules

Molecules that display a symmetrical distribution of electron density, leading to a lack of permanent electric dipoles, and thus do not have charged ends.

Vapor pressure

The pressure exerted by a vapor in a closed container that is in equilibrium with its liquid or solid phase, representing the tendency of particles to escape from the liquid phase into the vapor phase at a specific temperature.

Phase changes

Physical transformations that substances undergo, which include melting (solid to liquid), freezing (liquid to solid), vaporization (liquid to gas), condensation (gas to liquid), sublimation (solid to gas), and deposition (gas to solid), influenced by temperature and pressure variations.

Hydrogen bonding (more)

Responsible for the high boiling point which usually increases with increasing mass, and low density of water in its solid form.