Phases of matter: Comparison Property Solid Liquid Gas Particles Closely packed High density (But…Water is different!) More densely packed than in gas Most compressible-least densely packed Particle movement Vibrate weakly around fixed positions Lowest kinetic energy Can change positions with other particles Highest kinetic energy Intermolecular forces Most effective (strongest) Stronger than in gases Least effective (weakest) Shape and volume Both definite Definite volume only No definite shape or volume Mullis

Surface tension Force that pulls adjacent parts of a liquid surface together. The higher the attractive forces between particles in the liquid, the higher the surface tension. Hydrogen bonds make water have higher surface tension than most liquids. Soap Water droplet Mullis

Solids Crystalline solids: Particles are arranged in an orderly, geometric, repeating pattern. Examples: Emerald, diamond, calcite Amorphous solids: (Without shape) Particles are arranged randomly. Examples: Glass, plastic Mullis

Changing states Equilibrium: When there is no net change in a system. Dynamic equilibrium: When a vapor is in equilibrium with its liquid as one molecule leaves the liquid to become a vapor, another molecule leaves the vapor to become a liquid. In other words, an equal number of molecules will be found moving in both directions. Mullis

LeChâtelier’s Principle When a system at equilibrium is disturbed by application of stress, it attains a new equilibrium position that minimizes the stress. "If stress is applied to a system at equilibrium, the system will tend to readjust so that the stress is reduced." Mullis

Boiling Point Vapor pressure: Pressure exerted by a vapor = Pressure of the liquid at given temperature Liquid boils when its vapor pressure equals pressure of the atmosphere. Boiling is the conversion of a liquid to vapor within the liquid as well as at its surface. Boiling point is the temperature at which the equilibrium vapor pressure of the liquid equals the atmospheric pressure. Volatile liquids are liquids that evaporate readily. Mullis

Boiling Point, cont. High elevation: Low atmospheric pressure Low atmospheric pressure = lower boiling point High pressure in pressure cooker = increased boiling point, faster cooking If pressure above liquid increases, the liquid temperature rises until it matches the new pressure and boils again. Mullis

Separation by Distillation Distillation is the separation of liquid substances according to their different boiling points. As a liquid mixture is heated, the substance with the lower boiling point will vaporize first. Distillate: Condensed liquid substance Mullis

Kinetic Energy and Equilibrium Vapor Pressure In the beginning: # particles condensing to liquid phase = # particles evaporating to gas phase Increase temp Increase kinetic energy Now, more molecules have enough energy to leave the liquid. More vapor molecules = higher vapor pressure Equilibrium will soon be established, but at a higher vapor pressure. Mullis

Phase Diagram A phase diagram is a graph of pressure vs Phase Diagram A phase diagram is a graph of pressure vs. temperature that shows the conditions under which phases of matter exist. Critical temp (Tc): Above this, the substance cannot exist in the liquid state. Mullis

Four major "points" on a phase diagram Triple point, TP - All three phases can exist in equilibrium at this temperature and pressure. (The solid-liquid line and the liquid-vapor line meet.) Normal boiling point, Tb - The temperature at which the vapor pressure of a liquid is equal to standard atmospheric pressure. (Standard atmospheric pressure line crosses the liquid-vapor line.) Normal melting point, Tm - The temperature at which the vapor pressure of the solid and the vapor pressure of the liquid are equal. (Standard atmospheric pressure line crosses the solid-liquid line.) Critical temperature, Tc - The temperature above which no amount of pressure will liquefy a vapor. (The liquid-vapor line becomes vertical.) Mullis