Chapter 11 Phases of Matter

Kinetic Theory of Gases 1.Gases are mostly empty space. Gas particles have negligible volumes. No forces of attraction or repulsion between gas particles. 2.Gas particles are in constant motion. 3.Collisions between gas particles are perfectly elastic.

Gas Pressure Gas Pressure: force exerted by a gas per unit surface area of an object. –The collisions from the gas particles create a pressure in the system that is containing the gas particles Vacuum: an empty space with no particles and no pressure.

Pascal (Pa) Pascal: is the SI unit of pressure Standard pressure measured using pascals is 101.3kPa (kilapascals) Standard atmosphere (atm) is the pressure required to support 760mm Hg in a mercury barometer at 25C. 1atm = 760mm Hg = kPa

Problems With Pressure A gas is at a pressure of 1.50atm. Convert this to pressure. –In Kilopascals –In millimeters of mercury 1.5 atm x kPa = kPa 1 atm 1.5 atm x 760 mm Hg = 1140mm Hg 1 atm

The Nature of Liquids Molecules have the ability to move past one another like gas molecules. The particles that make up liquids vibrate and spin while they move from place to place. The attractive forces between liquid molecules are called intermolecular forces. –There are no forces like these that exist in gas molecules

The Nature of Liquids

Evaporation Vs. Vaporization Evaporation: When liquid converts to gas when the temperature of the liquid is not boiling. Vaporization: The conversion of a liquid to a gas or a vapor through out the whole substance

Vapor Pressure Evaporation of a liquid in a closed container creates a vapor pressure. When a partially filled container of liquid is sealed, some of the liquid will vaporize creating particles that will collide with each other and the walls of the container creating a vapor pressure. Vapor Pressure (definition): force dues to the gas above the liquid in a sealed container.

Boiling Point Boiling Point: the temperature at which the vapor pressure of the liquid is equal to the external pressure –Bubbles of vapor form throughout the liquid, rise to the surface and escape into the air as the liquid boils Normal Boiling Point: the boiling point of a liquid at a pressure of 101.3kPa.

Nature of Solids

Solid particles do not move around the space they contain. Solid particles vibrate around fixed points. Most solids are packed tightly together in an organized matter.

Nature of Solids After heating solids— –The particles begin to vibrate more rapidly as their kinetic energy increases. –The organization of solid particles begins to break down creating a liquid. Melting point (mp): is the temperature at which a solid turns into a liquid. –Ionic solutions have high melting points Because relatively strong forces hold them together.

Crystal Structure Crystal: the atoms, ions, or molecules that make up the solid substance are arranged in an orderly, repeating, three- dimensional pattern called a crystal lattice. –Most solids form crystals.

Allotropes Allotropes: two or more different molecular forms of the same element in the same physical state.

Amorphous Solids Not all solids form crystalline structures. Amorphous solids: lack an ordered internal structure. –Ex: rubber, plastic and asphalt are amorphous solids. Disordered, amorphous solid structure of silica glass.

Amorphous Solids  Glasses Glasses are transparent fusion products of inorganic substance that have cooled to a rigid state without crystallizing. –Glasses can sometimes be called super- cooled liquids –The irregular internal structure of glasses are intermediate between those of a solid crystalline structure and a free-flowing liquid.

Phase Diagrams A phase diagram gives the conditions of temperature & pressure at which a substance exists as solid, liquid, & gas The triple point describes the conditions at which all 3 phases are in equilibrium with each other

Phase Diagram

Changing States of Matter Gas  Liquid: –Condensation: the lose of energy from gas molecules to form a liquid Liquid  Gas: –Evaporation: the process of gaining energy at the surface of a liquid to turn individual molecules into a gas. –Boiling: the highest point at which a liquid will remain a liquid. –Vaporization: the process of any liquid molecule turning into a gaseous molecule. Boiling and Condensing are the same value but opposite in value based on the direction the energy is flowing in.

Changing States of Matter Liquid  Solid –Freezing: the process of releasing energy to reduce/stop the movement of the liquid molecules until the molecules are pulled close forming a solid. Freezing and melting point are the same value but opposite of each other based on the direction the energy is moving Solid  Liquid –Melting: the process of absorbing energy to increase the movement of molecules until the molecules move in a flowing motion.

Sublimation Sublimation is the process of making a solid to a vapor without passing through the liquid state.

Forces of Attraction: Ionic Ionic compounds generally have higher forces of attraction than covalent compounds. –the ions form opposite charges which allows the atoms to attract to each other.

Forces of Attraction: Covalent Intermolecular Forces: any attraction between 2 nonmetal elements. –Three forms London Dispersion Forces  (also known as induced dipole interactions) Dipole-dipole interactions

London Dispersion Forces  Induced Dipole Dipole: an uneven distribution of electrons within a molecule (covalent) –A polar molecule is a dipole –A nonpolar molecule is NOT a dipole. An induced dipole force occurs within a nonpolar molecule when the electrons are TEMPERARILY not shared evenly.

Dipole-Dipole Interactions Dipole = polar –A polar molecule is also referred to as a dipole- dipole interaction because the 2 or more nonmetals have a difference in electronegativity causing a partial negative and partial positive charge.

Hydrogen Bonding Hydrogen Bonding is a type of Dipole- Dipole interaction. It occurs between hydrogen and Fluorine, Oxygen and Nitrogen.