Gases, Liquids, And Solids - Saddleback College
Gases, Liquids, and SolidsChapter 5
Educational Goals1. Define, compare, contrast the terms specific heat, heat offusion, and heat of vaporization. Know the equations thatinvolve these concepts and be able to use them incalculations.2. Describe the meaning of the terms enthalpy change,entropy change, and free energy change. Explain if aprocess is spontaneous or not based on the free energychange.3. Convert between pressure units of atm, torr, and psi.4. List the variables that describe the condition of a gas andgive the equations for the various gas laws.
Educational Goals (cont.)5. Explain Dalton’s law of partial pressures.6. Define the terms density and specific gravity. Given thedensity, and either the mass or volume, be able todetermine the volume or mass (respectively).7. Know that a liquid will boil when its vapor pressure isequal to the atmospheric pressure.8. Describe, compare, and contrast amorphous solids andcrystalline solids.9. Describe the makeup of the four classes of crystallinesolids.
Phases of Matter and EnergyExample: Three phases of watersolidliquidgasicewatersteamH2O(s)H2O(l)H2O(g)
Why are some molecular compounds solidwhile others are gaseous and others areliquid at room temperature?Competing Powers Intermolecular forces working to holdparticles together as liquids or solids Kinetic Energy Motion Temperature,work to separate particlesKinetic Energy Temperature
One major factor that is responsible forthe varied behavior of solids, liquids, andgases is the nature of the interaction thatattracts one particle (atom, ion, ormolecule) to another.
What forces hold matter together tomake liquids and solids?
What forces hold matter together tomake liquids and solids?The attractive forces that hold moleculestogether are called Intermolecular forces.
3 Types of Intermolecular Forces1) Dipole-Dipole Forces2) Hydrogen Bonding3) London Forces– also called Induced Dipole Forces
Other Noncovalent InteractionsNoncovalent interactions are interactionsthat do not involve the sharing of valenceelectrons (covalent bonding).Other noncovalent interactions due to the attractionof permanent charges. 1) Salt bridges 2) Ion-dipole interactions
A salt bridge is another name for ionic bond.Ion-dipole interactions occur between ions witha full charge and atoms with a partial charge.
Energy meets MatterAdding energy to liquids will overcome theforces holding the molecules together– boilingAdding energy to solids will overcome theforces holding the molecules together– melting
Phase Changes Language
To reduce a fever, rubbing alcohol (2propanol) can be applied to the skin.As the alcohol evaporates (liquidbecomes a gas), the skin cools.Explain the changes in heat energy asthis process takes place. Note: 2-propanolvapors are flammable, so care must be takenwhen using this technique.
Units of Energy One calorie is the amount of energy neededto raise the temperature of one gram ofwater by 1 C joule– 4.184 J 1 cal In nutrition, calories are capitalized– 1 Cal 1 kcal 1000 cal
Converting Between Calories and JoulesExample: Convert 60.1 cal to joulesEquivalence statement: 1 cal 4.184 J1 cal4.184 J60.1 cal4.184 J1 calConversionFactors4.184 J1 cal 251 J
Calculations InvolvingHeat Energy One of two things will happen if energy is added orremoved from matter (assuming no chemicalchange takes place).– 1) Change the phase of the substance– Example: melt, freeze, vaporize (boil)– 2) Change the temperature of the substance You can only do one of these at a time!!!– See graph on the next slide
1) Phase ChangesEnergy calculations for phase changes may be carried outusing the tabulated values for: heat of fusion (symbol Hfus) for a substance (Table 5.2). Energy required to melt one gram of a solid Change sign to negative for freezing (liquid to solid)
1) Phase ChangesEnergy calculations for phase changes may be carried outusing the tabulated values for:§ heat of vaporization (symbol Hvap) of a substance Energy required to vaporize one gram of a liquid Change sign to negative for gas going to liquid
Calculations InvolvingChanging the PhaseEnergy Change (mass) x (heat of fusion or vaporization)Delta ( ) means“change in ”ΔE m x (Hfus or vap)Get from a table
Calculations InvolvingHeat EnergyExample: Determine the amount of energy neededto melt 155 g of ice at 0 C, we use the heat offusion of water (79.7 cal/g) as a conversion factor.ΔE (mass) x (heat of fusion)155 g x79.7 cal 1.24 x 104 calgNote: No Temperature Change!Ice (0oC) Water (0oC)
Group WorkA patient with a fever is sponged with 50.0 gof 2-propanol. How much energy is drawnfrom the patient when 2-propanol vaporizes?(heat of vaporization for 2-propanol is 159 cal/g)
2) Changing Temperature of Matter The amount the temperature of an object increasesdepends on the amount of energy added (Q).– If you double the added heat energy the temperaturewill increase twice as much. The amount the temperature of an object increasesdepends on its mass.– If you double the mass it will take twice as much heatenergy to raise the temperature the same amount.
Calculations InvolvingChanging the Temperature Energy calculations may be carried out using thevalues for the specific heat of a substance. Specific heat is the amount of energy required to raisethe temperature of one gram of a substance by oneCelsius degree.
Energy required Specific Heat x Mass x Temperature ChangeQ Sxmx(ΔT) is always:(final) – (initial)( T) Tfinal-TinitialJBy definition, the specific heat of water is 4.184g C
Example:Calculate the amount of heat energy (in joules)needed to raise the temperature of 7.40 g ofwater from 29.0 C to 46.0 CQ S x m x ΔTSpecific heat of water:Mass 7.40 g4.184 Jg oCTemperature Change (ΔT) 46.0 C – 29.0 C 17.0 CQ 4.184 Jg oC(7.40 g) (17.0 oC) 526 J
Group WorkHow much energy needs to be removed from 175 gof water to lower the temperature from 23.0oC to15.0oC ?
How much energy is required to convert 25g ofice at -7.0oC to water at 50.0oCIce-7.0oCStep 1Ice0.0oCTemperature ChangeQ1 Sicexmx( T)Step 2Water0.0oCWater50.0oCStep 3Phase ChangeTemperature Change E2 mxHfusQ3 Swaterxmx( T) Energy Total Q1 E2 Q3
New Topic:Will a change occur?Spontaneous vs. Nonspontaneous Changes An important question to ask is why some changesare:– spontaneous (continue to occur once they are started)OR– nonspontaneous (will not run by themselves unlesssomething keeps them going). Energy is the key factor in determining this.
Spontaneous vs. Nonspontaneous ChangesSpontaneousvs. Nonspontaneous
Energy vs. Free EnergyThe energy (E) of matter depends on the position(potential energy) and velocity (kinetic energy) ofevery molecule in the system.E Epotential EkineticThis is not practical to measure in the lab or tomodel in calculations!When working at constant temperature andpressure, it is mathematically convenient andexperimentally practical to look at the:Free Energy (G)
Energy vs. Free EnergyJust like the energy (E), in nature, given thechance, everything proceeds to the lowestpossible free energy (G)!
Free Energy (G)The “free energy” (ΔG) of a process can bethought of as the potential for change . G Gf - GiA spontaneous process has a negative G and anonspontaneous process has a positive G.
Gases and PressuresProperties of GasesHow to visualize a gas:Gas molecules or atoms are very far apart fromone another. different from liquids and solids!! Gas particles move in a straight line until theycollide with another particle or the container wall.
Properties of GasesGases Have Low DensityBecause of the relatively large distancesbetween gas particles, most of the volumeoccupied by a gas is empty space.
Properties of GasesGases completely fill their container.Except for a few very heavy gases, mostgasses will completely fill their container.
Properties of GasesGases Are Highly CompressibleGases arecompressibleLiquids and Solidsare not
Properties of GasesGases Are Highly CompressibleCompressibility is the ability to make thespace a substance takes up become smaller.
Properties of GasesGases can diffuse. Gaseous molecules travel at high speeds in alldirections and mix quickly with molecules of gasesin the air in a process called diffusion. Diffusion is the movement of onesubstance within another substance untilit is evenly distributed.
Properties of GasesExamples of diffusion. Ammonia Skunk in da house
Gas Pressure Pressure total force applied to a certain area– larger force larger pressure Gas pressure is caused by gas moleculescolliding with container walls or surfaces.
Air Pressure Constantly present when air present Decreases with altitude– less air
Air Pressure Measured using a barometer– Column of mercury supported by air pressure– Force of the air on the surface of the mercury balanced by thepull of gravity on the column of mercury
Various Units for Gas Pressure 1) atmosphere (atm)2) height of a column of mercury (mm Hg, in Hg)3) Torr4) Pascal (Pa)6) pounds per square inch (psi, lbs./in2)
Units we will use for pressure: Atmospheres (atm) Pounds per square inch (psi) Millimeters of mercury (mm Hg)– also called torr (1mm Hg 1 Torr)760. mm Hg1 atm760. Torr1 atm14.7 psi1 atmRelationships:1 atm 760. mmHg1 atm 760. Torr1 atm 14.7 psi1 atm760. mm Hg1 atm760. Torr1 atm14.7 psi
Pressure Unit ConversionsA pressure of 690. Torr is how manyatmospheres?1 atm 760 Torr690. Torr1 atm760 Torr .908 atm
Group WorkA pressure of 35.0 psi is how many atm?1 atm 14.7 psiA pressure of 812 mm Hg is how manyatmospheres?1 atm 760. mm Hg
Gas Laws
Instructional GoalsUnderstand and be able to use the following gaslaws in calculations: Boyles Law (relationship between pressure and volume) Charles’ Law (relationship between volume andtemperature) Gay-Lussac’s Law (relationship between pressure andtemperature) Avogadro’s Law (relationship between moles and volume) Combined Gas Law (relationship between pressure,volume and temperature) Ideal Gas Law (relationship between pressure, volume,number of moles, and temperature)
The Gas Laws The gas laws are the mathematicalequations that show the relationshipbetween volume, temperature, pressure,and amount of gas. As with all laws, they were discoveredby experiments.
Boyle’s Law Boyle studied the relationship between volume andpressure. The inverse relationship between pressure andvolume is known as Boyle’s law.
Boyle’s Law When the volume decreases, thepressure increasesPressure Gagelowhigh
Boyle’s Law When the volume increases, the pressuredecreasesPressure Gagelowhigh
Boyle’s Law Boyle also noticed that when the pressure and/or volume of a gas is changed the product ofthe pressure and volume remains the same. P V Constantx
InitialpressureInitialvolumeFinalFinalpressure volumeP1 V1 P2 V2Boyle’s Law
Remember that when using Boyle’sLaw, that the temperature is neverchanging. Only the pressure and volume change.
ExampleThe initial volume of the gas in the piston below is 3.00 litersand the initial pressure is 1.00 atm.The piston compressed (at constant temperature) to a new finalvolume of 1.00 L. What is the final pressure?Pressure Gagelowhigh
SolutionP1 V1 P2 V2P1 V1 P2 V2V2V2P1 1.00 atm P2 ?V1 3.00 LP2 P1 V1V2 V2 1.00 L(1.00 atm) (3.00 L)(1.00 L) 3.00 atm
Group WorkIf the syringe shown has an initial volume of 0.50mL and the gas in the syringe is at a pressure of1.0 atm, what is the pressure inside the syringe ifyour finger is placed over the opening and theplunger is pulled back to give a final volume of3.0 mL?
Charles’ Law Charles observed that as the temperature increases, thevolume increases and vice versa.Jacques Charles (1746-1823 ) The direct relationship between temperature and volumeis known as Charles’ law.
Charles’ LawWhen the temperature increases, the volume increases
Charles’ LawWhen the temperature decreases, the volume decreases
Charles’ Law Charles also noticed that ratio of volume totemperature of a gas is always the same.V ConstantT
Charles’ Law
Charles’ LawInitialvolumeInitialtemperatureV1T1 V2T2FinalvolumeFinaltemperature
Remember that when using Charles’ Law,that the pressure is never changing.– Only the temperature and volume change. Temperature must be Kelvin (K).– Kelvin temperature scale is always positive– K oC 273.15
ExampleThe initial volume of the gas in the piston below is 1.35 litersand the initial pressure is 1.00 atm.The temperature is lowered from 373 K to 250. K (at constantpressure). What is the final volume?Pressure Gagelowhigh
SolutionV2V1 T2T1V2 T2 V1T1 V1 1.35 LV2 ?T1 373 KT2 250. KT2 V1T1 (250.K) (1.35 L)(373K)V2 T2T2 0.905 L
Group WorkA balloon is inflated to 665 mL volume at 27 C.It is immersed in a dry-ice bath at 79 C. What isits volume, assuming the pressure remainsconstant?V2V1 T2T1Remember to convertto Kelvin (K)K oC 273.15
Gay-Lussac’s LawGay-Lussac’s observed that as the temperatureincreases, the pressure increases and vice versa.Joseph Gay-Lussac (1778–1850) The direct relationship between temperatureand pressure is known as Gay-Lussac’s Law.
Gay-Lussac’s Law When the temperature decreases, the pressuredecreases.Pressure Gagelowhigh
Gay-Lussac’s LawWhen the temperature increases, the pressureincreases.Pressure Gagelowhigh
Gay-Lussac’s Law Gay-Lussac also noticed that ratio of pressureto temperature of a gas is always the same.P ConstantT
Gay-Lussac’s LawInitialpressureInitialtemperatureP1T1 P2T2FinalpressureFinaltemperature
Remember that when using Gay-Lussac’sLaw, that the volume is never changing.– Only the temperature and pressure change. Temperature must be Kelvin (K).
ExampleThe initial pressure of the gas in the container below is .870 torrand the initial temperature is. 300.K.The temperature is raised from 300. K to 1250. K (at constantvolume). What is the final pressure?Pressure Gagelowhigh
SolutionP1T1 P2T2 P1T2T1 P2 T2T2P1 0.870 torr P2 ?T1 300. KP2 T2 P1T1 T2 1250. K(1250. K)(0.870 tor)(300.K) 3.63 torr
Group WorkAn aerosol can containing gas at 25 atm and 22 Cis heated to 55 C. Calculate the pressure in theheated can.P1T1 P2T2Remember to convertto Kelvin (K)K oC 273.15
The Combined Gas Law Boyles’s, Charles’s, and Gay-Lussac’s Laws can becombined mathematically. The relationship between temperature, volume, and pressureis known as the Combined Gas Law.
The Combined Gas LawP1V1 P2V2 T1T2
ExampleAt an ocean depth of 33 ft, where the pressure is 2.0atm and the temperature is 285K, a scuba diverreleases a bubble of air with a volume of 6.0 mL.What is the volume of the air bubble when it reachesthe surface, where the pressure is 1.0 atm and thetemperature is 298 K ?
SolutionP1 V1 P2 V2 T2T1P1 2.0 atmP2 1.0 atmV1 6.0 mLV2 ?T1 285 KT2 298 KT2P1V1 (298 K)(2.0 atm)(6.0 mL)V2 13mLP2T1(1.0 atm) (285K)
Avogadro’s LawAvogadro’s observed that the volume of a gas isdirectly proportional to the number of gas molecules.Amedeo Avogadro (1776–1856) The direct relationship between moles of gasmolecules and volume is known as Avogadro’s Law.
Avogadro’s LawWhen the number of moles of gas decreases,the volume decreases.Pressure Gagelowhigh
Avogadro’s LawWhen the number of moles of gasincreases, the volume increases.Pressure Gagelowhigh
Avogadro’s Law Avogadro noticed that ratio of volume tothe number of moles of a gas is alwaysthe same.V Constantn
Avogadro’s LawInitialvolumeV1n1Initial # moles V2n2FinalvolumeFinal # moles
Remember that when usingAvogadro’s Law, that the pressureand temperature are never changing.– Only the number of particles andvolume change.
ExampleThe initial volume of the 3.5 moles of gas in acontainer is 1.5 L.Amadeo adds 2.0 moles of gas. (atconstant temperature and pressure). Whatis the final volume?
SolutionV1n1 V2n2 V1n1n2 V1 1.5 LV2 ?n1 3.5 moln2 5.5 moln2 V1(5.5 mol) (1.5 L)V2 n1 (3.5 mol)V2 n2n2 2.4 L
Group WorkA balloon has a volume of 2.4 L and contains0.12 moles of air. A child blows more air into theballoon until it has a final volume of 3.5 L. Howmany moles of gas are in the balloon?
Gas Law SummaryV2V1n1 n2Combined Gas LawP1 V1T1P2 V2 T2
The Ideal Gas LawNo gas perfectly obeys all four of these lawsunder all conditions.These assumptions work well for mostgases and most conditions.One way to model a gas’s behavior is toassume that the gas is an ideal gas thatperfectly follows these laws.
The Ideal Gas LawIf we combine all these equations,we get the Ideal Gas Law.P V CbxV CanPV RnTV CcTGas ConstantP CgT
The Ideal Gas LawThe gas constant (R) is a mathematicalcombination of all the individual gas law constants(Cb, Cc, Cg, Ca)PV RnTThe Ideal Gas Law is more commonly writtenas:PV nRT
The Ideal Gas LawThe previous gas laws we studied involveda change in either P, V, T, or n.P1T1 P2T2V1 V2 nn12P1 V1 P2 V2V1T1 V2T2
The Ideal Gas Law The ideal gas law is used for any gassystem, any time. No changes are involved in the equationPV nRT
The Ideal Gas LawThe value of R is: .0821 L.atmK.molPV nRT When using this equation you must havethe following units: Pressure atm Volume liters Temperature K
The Ideal Gas LawThere are 4 variables in this equation:PV nRTPressure Volume# MolesTemperatureIn problems, we will always be given 3 ofthe 4 variables, then solve for the unknownvariable.
Example: The Ideal Gas LawHow many moles of gas are contained in 11.2 liters at1.00 atm and 0.0 C?PV n RTatmP 1.00?n LV 11.2T 273.2K
Partial Pressure
Dalton’s law of partial pressure statesthat the total pressure of a mixture ofgases is the sum of the partial pressures ofits components.– The partial pressure of a gas in a mixture isthe pressure that the gas would exert if alone.Partial pressureof gas BTotalpressureP T PA PB PCPartial pressureof gas APartial pressureof gas C
When two gases are present, the total pressureis the sum of the partial pressures of thegases.
Partial PressuresThe partial pressure of each gas in a mixturecan be calculated using the Ideal Gas Lawfor gases A and B in a mixturenA x R x TnB x R x TPA PB VVthe temperature and volume of everythingin the mixture are the samentotal nA nBntotal x R x TPtotal PA PB V
Let’s Try It!A 1.00L flask contains 5.00 x 10-2 mol of neon and 5.00 x10-3 mol of argon. At 30.0 C, what is the partial pressure ofeach gas in atmospheres and what is the total pressure?
LiquidsViscosity is the resistance to flow.-It is related to the strength of the noncovalent interactionsbetween the molecules that make up the liquid - thestronger the attractions, the thicker the liquid.-Temperature has an effect on viscosity.-As temperature rises, the increase in the kinetic energyof the molecules in the liquid helps the molecules pullaway from one another - higher temperature produceslower viscosity.
Glycerol is able to form more hydrogenbonds than 2-propanol. That is why glycerolis thicker (more viscous) than 2-propanol.
Density of a liquid (or any other substance)is the amount of mass contained in agiven volume.md VDensity is the relationship between themass of a substance and its volume.
Vapor PressureDue to collisions that take place between particles(atoms or molecules) that make up a liquid,particles at the surface are continually evaporating being “bounced” off into the gas phase. At thesame time gas phase molecules are being trappedand converted to liquid.
Vapor Pressure The boiling point of a liquid is the temperatureat which the vapor pressure of th
particles together as liquids or solids Kinetic Energy Motion Temperature, work to separate particles Kinetic Energy Temperature . One major factor that is responsible for the varied behavior of solids, liquids, and gases is the nature of the interaction that . This is not practical to measure in the lab or to model in calculations .
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