Chapter 11 - Intermolecular Forces and Liquids and Solids

Phases are the multiple states of a chemical that exist in a system, according to chemists. * A phase is a homogeneous part of a system that is in contact with other sections but separated from them by a well-defined border.

The non-ideal behavior of gases is caused by intermolecular forces. * Intermolecular forces are forces that attract molecules together.
This transition from the gaseous to the liquid phase is known as condensation * Intramolecular forces, in contrast to intermolecular forces, hold atoms in a molecule together.
What chemists call van der Waals forces are dipole-dipole, dipole-induced dipole, and dispersion forces, named after the Dutch physicist Johannes van der Waals. * Dipole-dipole forces are attractive forces that exist between polar molecules, or molecules with dipole moments. * Ion-dipole forces, which attract an ion and a polar molecule to each other, are likewise explained by Coulomb's law.
Because the separation of positive and negative charges in the atom is caused by the vicinity of an ion or a polar molecule, the dipole in the atom is called an induced dipole. * Ion-induced dipole interaction is the attractive interaction between an ion and the induced dipole dipole-induced dipole interaction is the attractive interaction between a polar molecule and the induced dipole.
The crucial point is that dispersion forces, or attractive forces, are produced as a result of transient dipoles formed in atoms or molecules in this type of contact.

Surface tension is a measurement of the elastic force on a liquid's surface. * The amount of energy required to stretch or raise the surface area of a liquid by a unit area is known as surface tension.
Capillary action is caused by two types of forces. * The first is cohesion, which is the intermolecular attraction between molecules that are similar. * Adhesion is a force that attracts molecules that are unlike each other, such as those in water and those in the sides of a glass tube.
The idiom "slow as molasses in January" is based on a physical feature of liquids known as viscosity. * The viscosity of a fluid is a measurement of its resistance to flow.

Crystalline and amorphous solids are the two types of solids. * Ice is a crystalline solid with a rigid and long-range organization; its atoms, molecules, and ions are arranged in specific locations. * A crystalline solid basic repeating structural unit is the unit cell.
The number of atoms around an atom in a crystal lattice is known as the coordination number. * A simple cubic cell is the simplest, repeating unit in the array of spheres. * The body-centered cubic cell and the face-centered cubic cell are the other types of cubic cells.

Crystal Structures

X-ray diffraction investigations have taught us almost what we know about crystal structure. * The scattering of X rays by the units of a crystalline material is known as X-ray diffraction.

Ionic crystals have two distinguishing features * (1) they are made up of charged species * (2) the sizes of anions and cations are often significantly varied.

Types of Crystals

Glass and other amorphous materials lack a regular three-dimensional arrangement of atoms. * Amorphous refers to the resulting solid.
Glass is one of the most valuable and adaptable materials in human history. * It's also one among the oldest, with glass artifacts dating back to 1000 B.C. * An optically transparent fusion product of inorganic materials that has cooled to a rigid state without crystallizing is frequently referred to as glass.

Composition and Properties of Glass

When energy is added or removed from a substance, phase shifts, or transformations from one phase to another, occur.
A phase transition occurs when the molecules in a liquid have enough energy to escape from the surface. * Evaporation, often known as vaporization, is the transformation of a liquid into a gas.
Condensation, or the transition from gas to liquid, occurs when a molecule collides with the liquid surface and is confined by intermolecular forces in the liquid.
When the rates of condensation and evaporation are equal, a condition of dynamic equilibrium is established * The rate of a forward process is exactly balanced by the rate of the reverse process.
The equilibrium vapor pressure is the vapor pressure measured when condensation and evaporation are in a dynamic equilibrium.
The molar heat of vaporization (Hvar), defined as the energy (typically in kilojoules) required to evaporate 1 mole of a liquid, is a measure of the strength of intermolecular forces in a liquid.

Phase Changes

The temperature at which a liquid's vapor pressure equals the external pressure is known as the boiling point. * When the external pressure is 1 atm, a liquid's normal boiling point is the temperature at which it boils.
No matter how high the applied pressure, every substance has a critical temperature (Tc) above which its gas phase will not liquefy. * The critical pressure (Pc) is the lowest pressure required to cause liquefaction at the critical temperature.
Freezing is the process of turning a liquid into a solid and melting, or fusing is the process of turning a solid into a liquid. * The temperature at which solid and liquid phases coexist in equilibrium is known as the melting point of a solid or the freezing point of a liquid. * Supercooling is a phenomenon in which a liquid can be chilled to below its freezing point for a short time. * Sublimation is the transition of molecules from the solid-state to the vapor state. * A deposition is the inverse process, in which molecules go directly from vapor to solid. * The energy necessary to sublime 1 mole of a solid is known as molar heat of sublimation (Hsub).

A phase diagram is a single graph that depicts the general relationships between the solid, liquid, and vapor phases. * The conditions under which a substance exists as a solid, liquid, or gas are summarized in a phase diagram.
The triple point, which is the only situation in which all three phases can be in equilibrium with one another, is where all three curves meet.