Chem 1151: Ch. 6

States of Matter

Physical States of MatterPhysical States of Matter

Matter can exist as:SolidLiquidGas

Temperature Dependent

States

http://www.uni.edu/~iowawet/H2OProperties.html; http://en.wikipedia.org/;

Physical PropertiesPhysical PropertiesStates can be distinguished by different properties:Density: m/VShape: Physical dimensionsCompressibility: Volume change due to pressureThermal Expansion: Volume change due to temperature change

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011; http://en.wikipedia.org/;

Kinetic Molecular Theory of MatterKinetic Molecular Theory of MatterTheory to explain the behavior of matter in different states

1. Matter is composed of tiny particles (molecules)2. These particles are in constant motion and have kinetic energy (KE)3. The particles possess potential energy (PE) as a result of attracting or

repelling each other.4. The average particle speed increases as the temperature increases5. The particles transfer energy from one to another during collisions in

which no net energy is lost from the system.

m = mass (g, Kg)v = velocity = (Distance (m) /Time (s))

Kinetic EnergyKinetic Energy

1. Particles are in constant motion and have kinetic energy (KE)

m = mass (g, Kg)

v (nu)= velocity = (Distance/Time)

Calculate KE for two particles with masses of 2.00 g and 4.00 g if they are both moving with a velocity of 15 m/s.

Kinetic EnergyKinetic Energy

http://www.fightingmaster.com/masters/brucelee/chuck.htm

How Bruce Lee kicked the @#&*! out of Chuck Norris

Potential EnergyPotential Energy

http://water.me.vccs.edu/courses/env211/lesson2_print.htm; http://csep10.phys.utk.edu/astr161/lect/history/newtongrav.html

Potential energy results from attractions or repulsions of particles.GravityElectrostatic (charge)

Cohesive and Disruptive Forces in MatterCohesive and Disruptive Forces in Matter

http://water.me.vccs.edu/courses/env211/lesson2_print.htm

Cohesive forces: Associated with PE. Tend to attract particles towards each other.Temperature-independent

Disruptive forces: Associated with KE. Tend to scatter particles away from each other.Temperature-dependent

State of a substance depends on relative strengths of these forces

Solid StateSolid State

http://www.eduys.com/Copper-Molecular-Structure-Model-303.html; http://en.wikipedia.org/wiki/File:BridgeExpansionJoint.jpg

Graphite: Each Carbon is covalently bonded to 3 other carbons in ring

Diamond: Each carbon is bonded to 4 other carbons Copper

Characteristics of solids: •Cohesive forces stronger than disruptive forces•High Density•Definite Shape (strong cohesive forces)•Small Compressibility•Very small Thermal Expansion (particles vibrate but volume increases limited due to cohesive forces)

Bridge expansion joint

Liquid StateLiquid StateCharacteristics of liquids: •Particles packed randomly and close together•Particles in constant motion•Particles slide over each other but lack enough KE to separate completely•High Density (particles not widely separated)•Indefinite Shape (expand to shape of container)•Small Compressibility (very little space between molecules)•Small Thermal Expansion (particles vibrate, push away from each other, but volume increases limited due to cohesive forces)

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011

Gaseous StateGaseous State

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011; http://www.chemistry.wustl.edu/~edudev/LabTutorials/Airbags/airbags.html

Characteristics of gases: •Disruptive forces stronger than cohesive forces between particles•Particles in constant random motion•Particles far apart, travel in straight lines, collide frequently•Low Density (particles widely separated)•Indefinite Shape (little cohesion, particles expand to shape of container)•Large Compressibility (gas is mostly empty space)•Moderate Thermal Expansion (increase in temperature causes particles to collide with more energy, increases volume)

Gas LawsGas Laws

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011

• Describe behavior of gases when mixed, subjected to pressure or temperature changes, or allowed to diffuse

• Laws describes relationships between temperature (T), volume (V), pressure (P) and mass• Pressure (P) = Force/Area

•Boyle’s law•Charles’s law •Combined gas law

•Avogadro’s law •Ideal gas law

P, V, T RelationshipsP, V, T Relationships

Boyle’s Law•A constant relationship exists between pressure (P) and volume (V)

• If pressure increases, volume occupied by the gas decreases• If volume increases, pressure created by the gas decreases

Charles’s Law•At constant pressure, the volume of a gas sample is directly proportional to the temperature (expressed in kelvins)•If temperature increases, volume increases at constant pressure

P, V, T RelationshipsP, V, T Relationships

Charles’s Law•At constant pressure, the volume of a gas sample is directly proportional to the temperature (expressed in kelvins)•If temperature increases, volume increases at constant pressure

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011

P, V, T RelationshipsP, V, T RelationshipsCombined gas Law•Boyle’s law and Charles’s law can be combined to relate P, V and T

• Because k’’ is a constant, we can use this equation to evaluate changes in these variables over time (between some initial state and a final state)

Ideal Gas LawIdeal Gas Law• The combined gas law applicable when mass of gas remains constant

during changes in P, V and T• What happens when mass changes?

Avogadro’s law •Two different gases of equal volume measured at same T and P contain equal numbers of molecules•Mass would not be identical due to different MW’s

ideal gas law •Combines Boyle’s law, Charles’s law and Avogadro’s law

P = PressureV = Volumen = number of molesT = TemperatureR = Universal Gas Constant

Ideal Gas LawIdeal Gas Law

P = PressureV = Volumen = number of molesT = TemperatureR = Universal Gas Constant

Also, becausem = mass

MW = molecular weight

We can also express the ideal gas law as STP (Standard Temperature and Pressure)T = 0 °CP = 1.0 atmV of 1 mol gas (any gas) = 22.4 L at STP

PROBLEMSPROBLEMSExample 6.6, 6.7, 6.8, 6.9

Changes in StateChanges in State Transition of matter from one state to another (solidliquidgas)

Temperature-related Exothermic process: Heat released

Particles move closer together Stronger cohesive forces

Endothermic process: Heat absorbed Particles move farther apart Stronger disruptive forces

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011

Evaporation and CondensationEvaporation and CondensationEvaporation (vaporization): Molecules leave the surface of a liquidEndothermic processRate depends on temperature and surface area of liquidTemperature relates to speed and KE of molecules and their ability to escape cohesive forces at liquid surfaceEvaporating molecules carry KE away from water removes heat from remaining liquid

This is how sweating cools the body

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011

Condensation: Gas molecules converted to liquid or solid stateExothermic process

Evaporation and Vapor PressureEvaporation and Vapor PressureEvaporation (vaporization): Molecules leave the surface of a liquidCondensation: Gas molecules converted to liquid or solid state

In open system, liquid evaporates into atmosphere In a closed system, evaporation and condensation reach an equilibrium

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011

Vapor pressure: Pressure exerted by vapor in equilibrium with a liquidPressure is due to constant number of molecules exerting force on liquid and walls of containerFor water, increasing T increases vapor pressure (higher KE)Compounds that mix with water have lower vapor pressure than nonpolar compounds

Boiling and the Boiling PointBoiling and the Boiling Point

Vaporization occurs at surface of liquid As liquid heated, vapor pressure increases Boiling: When vapor pressure equals atmospheric pressure, vaporization

begins to occur beneath surface of liquid Boiling Point: Temperature when vapor pressure equals atmospheric

pressure If you decrease atmospheric pressure, boiling point decreases

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011

Sublimation and MeltingSublimation and Melting

Solids have low vapor pressures due to strong cohesive forces Vapor pressures increase with temperature

Sublimation: Vapor pressure of solid high enough for molecules to transition from solid directly to gas Ex. Freeze drying

Melting: Breakdown of solid into liquid state Melting Point: Temperature where solid and liquid have same vapor

pressure KE of solid particles large enough to overcome strong cohesive forces

holding particles together

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011

Energy and the States of MatterEnergy and the States of Matter KE (associated with particle motion) is related to heat PE is associated with particle separation distances, not motion Increase in T on adding heat increases KE of particles Adding heat with no increase in T increases PE of particles Adding heat may or may not result in T increase

AB Solid heated from -20 to 0 °CKE increases

BC Temp constant while solid meltsPE increases

CD Adding more heat increases temp KE increases

DE liquid vapor at 100 °CPE increases

EF Temp increases with heat of steamKE increases

Phase change

Phase change

Energy and the States of MatterEnergy and the States of Matter Specific Heat: Amount of heat (calories or joules) required to change the

temperature of a specified amount of substance (1 g) by 1 °C. 1 cal = 4.184 J Substance with high specific heat can absorb more heat with small temp.

change

Heat of fusion: Amount of heat (calories or joules) required to melt 1 g of substance at constant temperature

Heat of vaporization: Amount of heat (calories or joules) required to boil 1 g of substance at constant temperature

Ex: Heats of fusion and vaporization for water are 80 and 540 cal/g. This is why a steam burn is worse than burn by boiling water: higher

energy of steam that is released when steam condenses on skin.

Heat CalculationsHeat Calculations

Heat = (sample mass)(specific heat)(temp. change)

Specific Heat: Amount of heat (calories or joules) required to change the temperature of a specified amount of substance (1 g) by 1 °C.

1 cal = 4.184 J

Ex. 1. How much heat (in J) absorbed by 100.0 g of ethylene glycol if temperature changes from 30.0 °C to 85.0 °C?

Heat CalculationsHeat Calculations

Heat released = (sample mass)(specific heat)(temp. change)

Heat of vaporization: Amount of heat (calories or joules) required to boil 1 g of substance at constant temperature

1 cal = 4.184 J

Ex. 2. Calculate the heat released when 5.00 × 103 g of steam at 120 °C condenses to water at 100 °C.

Part 01 Heat associated with temp. change

Heat released = (sample mass)(heat of vaporization)Part 02 Heat associated with phase change