GEN CHEM Q3

kinetic-molecular theory

kinetic-molecular theory

is based on the idea that matter is composed of tiny particles that are always in motion

It helps to explain why matter exists in different phases (solid, liquid, and gas) and how matter can change from one phase to another.

state of a substance

depends on the balance between the kinetic energy of the individual particles (molecules or atoms) and the intermolecular forces.

kinetic energy

keeps the molecules apart and moving around, and is a function of the temperature of the substance

(KMT) Solid

Held rigidly in position with virtually no freedom of movement, It has less empty space and tightly packed,.

(Definite space, Definite volume)

(KMT) Liquid

Molecules are close together that there is a very little empty space and much more difficult to compress than gases.

(Indefinite space, Definite volume)

(KMT) Gas

Particles are far apart.

(Indefinite space, Indefinite Volume)

Intermolecular forces

are attractive forces that act between molecules or particles in the solid or liquid states. Generally, these attractive forces are much weaker than bonding forces.

Intramolecular forces (within molecules)

hold atoms together in a molecule. ______________ stabilize individual molecules. Generally, these forces are simply chemical bonds such as ionic and covalent bonding.

London Dispersion Forces (LDF)

(Gases and Non-Polar)

are intermolecular forces of attraction between all atoms and molecules, used to compress air molecules; Non-Polar molecules and Noble gases

LDF

also called "Van der Waals Force"

Dispersion Forces

are weak attractive forces that result from the continuous movement of electrons in particles.

Non-Polar Molecules

have zero dipole movement because their electron density in uniform and symmetrical. stable molecules equals amount of protons/electrons. (Ex: CH4 - Methane)

Dipole-Dipole Force

(Liquid/Covalent)

attractive forces between polar molecules. these are the attraction between the positive end of one molecule and the negative end of another.

Dipoles

form when there is a large difference in electronegativity between two atoms joined by a covalent bond.

Polar Molecules

Molecules that have an unequal distribution of charges

Electronegativity

A measure of the ability of an atom in a chemical compound to attract electrons

Hydrogen Bonding

(Polar Covalent Molecules)

Is a special case of very strong dipole dipole interaction. it is not a chemical bond in a formal sense; it only occurs in Hydrogen, Fluorine, Oxygen & Nitrogen.

Polar Covalent molecules, 5 to 10 times stronger compared to other dipole-dipole interactions.

Ion-Dipole Forces

(Ionic and Covalent Compounds)

are involved in the dissolution process, acts between one ion (either ion or cation) and a polar molecule.

Negative Ion

Anion

Positive Ion

Cation

Ion-Ion Force

Is used for solid molecules and ionic compounds

- it forms the lattice structure
- is the strongest of the 5 forces

weakest intermolecular force

(LDR) London Dispersion Force

Liquid

made up of particles that are close to each other and have kinetic energy, They are constantly moving and has a moderately high density since they occupy a fixed volume

Surface Tension

is the force that causes the surface of a liquid to contract. It is the property of the surface of a liquid that allows it to resist an external force due to the cohesive nature of its molecules.

it depends on the intermolecular force of attraction.

Viscosity

is the resistance of fluids to flow

The greater the resistance in flowing, the more vicious the liquid is.

Is expressed in units of centipoise.

Vapor Pressure

is a phase change from liquid to gas

Condensation

phase change from gas to liquid

Vapor

is used to refer to the gaseous phase of a substance, which is normally a liquid or solid at room temperature

Volatile

substances that evaporate readily; they have weak intermolecular forces of attraction. (Example: Alcohol, Gasoline, Paint-Thinner, Dry-Cleaning solvents)

they burn more readily since they easily combine with Oxygen.

Molar Heat of Vaporization

is the energy required to vaporize 1 mole of a liquid at a given temperature.

Boiling Point

The temperature at which a liquid turns into gas

Water

serves important purposes of life on earth. It is a remarkable substance with a unique set of properties that make it essential of life. It has the ability to exist in three states (Solid, Liquid, Gas)

Boiling Point and Freezing Point

(100 degrees C boiling point/0 degrees C freezing point)


The high boiling point of water is a consequence of its strong intermolecular forces of attraction caused by the formation of the H-Bond.

Specific Heat

Refers to the amount of water needed.

Cohesion

one of the most remarkable properties of water that arises from its unique molecular structure. Refers to the attraction between molecules of the same substance

Surface Tension

The cohesive forces at the surface of water creates __, which is the ability of a liquid to "stick together" at its surface.

Adhesion

Water molecules stick to other substances.

Thermal properties

Water absorbs or release more heat than many substances for each degree of temperature increase or decrease.

Heat of vaporization

The amount of energy required to convert a given amount of a substance from its liquid state to its gaseous state at a constant temperature.

Capillary Action

Cohesion combined with adhesion (attraction between different substances) contributes to __.