Created by C. Ippolito June 2007 States of Matter 13.1 The Nature of Gases 13.2 The Nature of Liquids 13.3 The Nature of Solids 13.4 Changes of State Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 The Nature of Gases Objectives Describe the assumptions of the kinetic theory as it applies to gases Interpret gas pressure in terms of kinetic theory Define the relationship between Kelvin temperature and average kinetic energy Updated 9/1/2019 Created by C. Ippolito June 2007

Kinetic Theory & a Model for Gases Kinetic Energy energy an object has because of its motion Kinetic Theory all matter consists of tiny particles in constant motion Gas Particles small, hard spheres of insignificant volume motion is rapid, constant, and random collisions are perfectly elastic Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 Gas Pressure result of force exerted by gas per unit surface area of an object from simultaneous collisions of billions of rapidly moving particles in an object Vacuum an empty space with no particles and no pressure Atmospheric Pressure from collisions of atoms and molecules in air Barometer measures atmospheric pressure SI unit is the pascal (Pa) Standard Atmosphere pressure to support 760mm of Hg at 25°C 1 atm = 760 mm Hg = 101.3 kPa Updated 9/1/2019 Created by C. Ippolito June 2007

Converting Between Units of Pressure Updated 9/1/2019 Created by C. Ippolito June 2007

Kinetic Energy and Temperature Average kinetic energy and temperature are related  kinetic energy  temperature  kinetic energy  temperature Kelvin temperature of a substance is directly proportional to the average kinetic energy of the particles of a substance Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 The Nature of Liquids Objectives Identify factors that determine physical properties of a liquid Define evaporation in terms of kinetic energy Describe equilibrium between a liquid and its vapor. Identify the conditions at which boiling occurs Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 Model for Liquid Intermolecular forces of attraction keep liquid particles close together interplay between disruptive particles in a liquid and the attraction of particles determine the physical properties of liquids Liquid particles are closer together than gases more dense than gases little affected by pressure Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 Evaporation Vaporization conversion of a liquid into a gas Evaporation process by particles at surface of liquid converts to gas without boiling only molecules with a certain minimum kinetic energy can escape from surface of liquid Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 Vapor Pressure measure of the force exerted by a gas above a liquid at constant vapor pressure, a dynamic equilibrium exists between the vapor and liquid. rate of evaporation = rate of condensation  temperature  vapor pressure Updated 9/1/2019 Created by C. Ippolito June 2007

Vapor Pressure Measurement Manometer measures vapor pressure Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 Boiling Point A liquid begins to boil, when heated to a temperature at which all of its particles have enough kinetic energy to vaporize Boiling Point temperature where vapor pressure of liquid = external pressure on liquid Updated 9/1/2019 Created by C. Ippolito June 2007

Boiling Point and Pressure Changes Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 Normal Boiling Point boiling point at 1 atm or 101.3 kPa Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 The Nature of Solids Objectives Evaluate how the way particles are organized explains the properties of solids Identify the factors that determine the shape of a crystal Explain how allotropes of an element are different Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 Model for Solids General properties of solids reflect an orderly arrangement of particles and the fixed location of particles Melting Point temperature at which a solid changes into a liquid Updated 9/1/2019 Created by C. Ippolito June 2007

Crystal Structure & Unit Cells shape of a crystal reflects the arrangement of the particles Crystal Systems Seven Systems Cubic, Tetragonal, Orthorhombic, Monoclinic, Triclinic, Hexagonal, Rhombohedral characterized in terms of angles between faces (α, β, γ) length of edges on each face (a, b, c) Unit Cell smallest group of particles that retain geometric shape of the crystal Simple Cubic Body Centered Face Centered Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 Allotropes two or more different molecular forms of the same element in the same physical state different properties different structures Carbon (diamond, graphite, fullerenes) Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 Changes of State Objectives Identify the conditions necessary for sublimation Describe how equilibrium conditions are represented in a phase diagram Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 Sublimation change of a substance from a solid to a vapor without passing through the liquid state occurs in solids with vapor pressures that exceed atmospheric temperature at or near room temperature Updated 9/1/2019 Created by C. Ippolito June 2007

Created by C. Ippolito June 2007 Phase Diagrams A graphic representation of the relationships among solid, liquid, and vapor states in a sealed container pressure and temperature at which two phases exist in equilibrium are indicated by a line separating the phases triple point the only set of conditions at which all three phases can exist at equilibrium Updated 9/1/2019 Created by C. Ippolito June 2007