Chem 1151: Ch. 6

1. Chem 1151: Ch. 6 States of Matter

2. Physical States of Matter • Matter can exist as: • Solid • Liquid • Gas Temperature Dependent States http://www.uni.edu/~iowawet/H2OProperties.html; http://en.wikipedia.org/;

3. Physical Properties • States can be distinguished by different properties: • Density: m/V • Shape: Physical dimensions • Compressibility: Volume change due to pressure • Thermal Expansion: Volume change due to temperature change Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011; http://en.wikipedia.org/;

4. Kinetic Molecular Theory of Matter Theory to explain the behavior of matter in different states Matter is composed of tiny particles (molecules) These particles are in constant motion and have kinetic energy (KE) The particles possess potential energy (PE) as a result of attracting or repelling each other. The average particle speed increases as the temperature increases 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))

5. Kinetic Energy 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.

6. Kinetic Energy How Bruce Lee kicked the @#&*! out of Chuck Norris http://www.fightingmaster.com/masters/brucelee/chuck.htm

7. Potential Energy • Potential energy results from attractions or repulsions of particles. • Gravity • Electrostatic (charge) http://water.me.vccs.edu/courses/env211/lesson2_print.htm; http://csep10.phys.utk.edu/astr161/lect/history/newtongrav.html

8. Cohesive and Disruptive Forces in Matter 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 http://water.me.vccs.edu/courses/env211/lesson2_print.htm

9. Solid State • 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 Diamond: Each carbon is bonded to 4 other carbons Graphite: Each Carbon is covalently bonded to 3 other carbons in ring Copper http://www.eduys.com/Copper-Molecular-Structure-Model-303.html; http://en.wikipedia.org/wiki/File:BridgeExpansionJoint.jpg

10. Liquid State • Characteristics 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, 7th Edition, 2011

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

12. Gas Laws • 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 Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

13. P, 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

14. P, 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, 7th Edition, 2011

15. P, V, T Relationships • Combined 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)

16. Ideal 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 = Pressure V = Volume n = number of moles T = Temperature R = Universal Gas Constant

17. Ideal Gas Law P = Pressure V = Volume n = number of moles T = Temperature R = Universal Gas Constant m = mass Also, because MW = molecular weight STP (Standard Temperature and Pressure) T = 0 °C P = 1.0 atm V of 1 mol gas (any gas) = 22.4 L at STP We can also express the ideal gas law as

18. PROBLEMS Example 6.6, 6.7, 6.8, 6.9

19. Changes in State • Transition of matter from one state to another (solidliquidgas) • 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, 7th Edition, 2011

20. Evaporation and Condensation • Evaporation (vaporization): Molecules leave the surface of a liquid • Endothermic process • Rate depends on temperature and surface area of liquid • Temperature relates to speed and KE of molecules and their ability to escape cohesive forces at liquid surface • Evaporating molecules carry KE away from water  removes heat from remaining liquid • This is how sweating cools the body • Condensation: Gas molecules converted to liquid or solid state • Exothermic process Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

21. Evaporation and Vapor Pressure • Evaporation (vaporization): Molecules leave the surface of a liquid • Condensation: 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 • Vapor pressure: Pressure exerted by vapor in equilibrium with a liquid • Pressure is due to constant number of molecules exerting force on liquid and walls of container • For water, increasing T increases vapor pressure (higher KE) • Compounds that mix with water have lower vapor pressure than nonpolar compounds Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

22. Boiling 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, 7th Edition, 2011

23. Sublimation 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, 7th Edition, 2011

24. Energy 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 °C KE increases BC Temp constant while solid melts PE increases Phase change CD Adding more heat increases temp KE increases Phase change DE liquid  vapor at 100 °C PE increases EF Temp increases with heat of steam KE increases

25. Energy 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.

26. Heat Calculations • 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 = (sample mass)(specific heat)(temp. change)

27. Heat Calculations • 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)(specific heat)(temp. change) Part 02 Heat associated with phase change Heat released = (sample mass)(heat of vaporization)