Chapter 13 States of Matter Solids, Liquids and Gasses

The Kinetic Molecular Theory Basic Assumptions Particle Size Gas particles have no volume (pin point particles) The space between particles is extremely large compared to the volume of the particles. Due to this distance, there is no significant attractive or repulsive force acting on the particles.

The Kinetic Molecular Theory Basic Assumptions Particle Motion Gas particles are in constant random motion. Collisions between particles are elastic (Energy can be transferred from one particle to another during a collision, but no energy is lost when particles collide)

Gas Pressure The force that a gas exerts per unit area as a result of the simultaneous collisions of many particles No particles = no pressure = The Mercury Barometer a vacuum Invented by Evangelista Torricelli Two forces affect the height of the mercury column Gravity and Atmospheric Pressure Equivalent pressure units 760 mm Hg = 101.3 kPa = 1atm = 760 torr = 14.7 psi

Kinetic Energy and Temperature Average Kinetic Energy of particles in a substance is directly proportional to the Kelvin temperature of a substance.

13.2 The Nature of Liquids Particle Spacing Intermolecular attractions reduce the amount of space between particles in a liquid. Particle Motion Particles in a liquid have enough kinetic energy to flow The tendency for particles move and their attraction for one another account for the physical properties of liquids

Vaporization vs. Evaporation Vaporization is the conversion of a liquid to a gas Evaporation is vaporization that occurs at the surface of a liquid that is not boiling. Evaporation depends on the intermolecular forces that hold the particles in a liquid together. If the forces are weak, then the kinetic energy of the particles at the surface can overcome the intermolecular forces that hold them together. Adding heat will increase the rate of evaporation of a liquid

Vapor Pressure Vapor pressure is a measure of the forced exerted by a gas over a liquid. Vapor pressure is created in a closed system as particles in a liquid evaporate and collide with the walls of the container. There is a direct relationship between temperature and vapor pressure. Manometer

Boiling Boiling occurs at the temperature when the vapor pressure of a liquid equals the pressure exerted by the atmosphere. The boiling point of a liquid is when the liquid changes from a liquid to a gas Not all substances boil at the same temperature because of intermolecular attractions.

The Nature of Solids Particles are arranged in an orderly fashion with fixed locations within a solid. Heat increases the kinetic energy of particles in a solid which causes the organization of the solid to break-down = Melting. The melting point of a solid is the temperature at which a solid changes into a liquid.

The Structure of Solids Most solids are crystalline The unit cell is the smallest group of particles in a crystal that retain the geometric shape of the crystal There are 7 crystal systems

Allotropes and Amorphous Solids Allotropes are solid substances that can exist in more than one form in the same physical state. Allotropes of Carbon Amorphous Solid Amorphous solids lack an ordered internal structure

Heating Curve and Change of State

Endothermic Phase Changes Melting- solid absorbs energy until particles have enough speed to break free of IM forces holding them in place Vaporization-liquid absorbs energy until particles have enough speed to break free of IM forces holding them close together Sublimation – Solids are converted directly to gases without forming a liquid

Exothermic Phase Changes Freezing – liquid particles release energy and particles become highly organized Condensation-gases lose energy and particles come close enough together to experience intermolecular forces Deposition – Process by which a gas turns into a solid without the formation of a liquid

Phase Changes

Phase Changes

Phase Diagrams Phase diagrams show the temperature and pressure conditions at which a substance exists as a solid, liquid, or gas Triple oint