States of Matter & Energy Thermochemistry: States of Matter & Energy

Phases of Matter From a solid to a liquid: Temperature increases Attraction between particles decrease

Phases of Matter Solids Definite volume and shape Attraction between molecules: High Ability for molecules to move: Low (tend to vibrate in place)

Phases of Matter Liquid Definite volume; no definite shape Attraction between molecules: Medium Ability for molecules to move:

Phases of Matter Gas No definite volume or shape Attraction between molecules: Low Ability for molecules to move: High

Phase Changes Sublimation Melting Boiling (fusion) (vaporization) Freezing Condensation Deposition

Heating/Cooling Curve Shows the temperature and energy of a substance over time as it changes from a solid to a gas To increase the temperature we must add energy.

Energy Temperature is a measure of the average kinetic energy of the particles. Kinetic energy = energy of motion Heat is the flow of energy from one object to another As we add heat energy: Kinetic energy of the particles increases, and temperature increases

Energy In solids, liquids, and gases: As the average kinetic energy of the particles changes, the temperature changes ∆ KE = ∆ Temperature

Phase Changes Melting point Freezing point Added heat energy allows particles to move around and overcome intermolecular attraction As molecules move away from each other, solid becomes a liquid There is no temperature change until all of the solid changes to a liquid Freezing point Heat is lost, and attractive forces pull molecules closer together to form solid There is no temperature change until all of the liquid changes to a solid

Phase Changes Heat energy during the melting phase is being used to overcome attractive forces between molecules Solid phase: molecules stay in place and vibrate Liquid phase: molecules can flow past each other With a phase change, there is a change in potential energy (energy of position of molecules next to each other)

Phase Changes Melting point and freezing point are at the same temperature Melting: PE increases Freezing: PE decreases Boiling point and condensation point are the same temperature Boiling: PE increases Condensation: PE decreases Each substance has its own characteristic melting/freezing point

Heat The amount of heat needed depends on: Identify each phase and energy type (KE/PE) for sections a, c, and e: e d Temp. c b a Time How much heat is needed to raise the temperature in a solid, liquid, or gas? The amount of heat needed depends on: How much substance you have (mass) How much you want to change the temperature ( Temp) The substance itself

Specific Heat q = mC T a: CpIce = 2.03 J/gC c: CpWater = 4.184 J/gC d Temp. c b a Time q = mC T q = heat m = mass T = change in temp. C = specific heat a: CpIce = 2.03 J/gC c: CpWater = 4.184 J/gC e: CpWater Vapor = 2.00 J/gC

Specific Heat How much heat is required to change 10.0 g of water from 20.0C to 50.0C? q = m C T q = (10.0 g) (4.184 J/gC)(50.0C - 20.0C) q = (10.0 g) (4.184 J/gC)(30.0C) q = 1255.35 or 1260 J

Specific Heat How much heat is required to change 10.0 g of ice from -30.0C to -10.0C? q = m C T q = (10.0 g) (2.03 J/gC)(-30.0C - -10.0C) q = (10.0 g) (2.03 J/gC)(20.0C) q = 406 or 410 J

Heat of Fusion/Vaporization Identify each phase and energy type (KE/PE) for sections b and d: e d Temp. c b a Time How much heat is needed to change a solid to a liquid, or a liquid to a gas? The amount of heat needed depends on: How much substance you have (mass) The substance itself

Heat of Fusion/Vaporization d Temp. c b a Time q = m H q = heat m = mass H = heat of fusion or heat of vaporization (No temp. change) b: Hfus = 340 J/g d: Hvap = 2260 J/g

Heat of Fusion How much heat is needed to melt 25.0 g of ice? q = m Hfus q = (25.0 g)(340 J/g) q = 8500 J

Heat of Vaporization How much heat is needed to evaporate 25.0 g of water? q = m Hvap q = (25.0 g)(2260 J/g) q = 56500 J

Heat of Solution Heat of solution The heat produced by a chemical reaction, or the heat required for a chemical reaction to occur Heat is absorbed from the atmosphere or released into the atmosphere

Heat of Solution Endothermic reaction Exothermic reaction Requires heat energy from the environment to get reaction to run Heat is transferred from the environment to the reaction Is a positive value Exothermic reaction Produces heat Heat is transferred from the reaction to the environment Is a negative number

Heat of Solution problem What is the enthalpy of solution in KJ/mol if 6.34 g of KOH is dissolved into 98.4 g of water. The temperature of the water changes from 24.5oC to 22.0oC. Is this exothermic or endothermic?

Boiling Point Does water always boil at 100ºC? Boiling point: NO. Boiling point depends on atmospheric pressure Boiling point: Is the temperature at which vapor pressure of the liquid is the same as the atmospheric pressure Pressure of the bubbles = air pressure in the room