phases of matter liquids, solids (crystals) & solutions colligative properties dr. ron rusay...

Phases of Matter Liquids, Solids (Crystals) & Solutions

Colligative Properties

Dr. Ron Rusay

Intermolecular Forces I

• Changes of State– Phase transitions

– Phase Diagrams

• Liquid State– Pure substances and colligative properties of solutions,

which depend upon the ratio of the number of solute particles to the number of solvent molecules in a solution. They are independent of the nature of the solute particles.

Intermolecular Forces: Phases of Matter & Colligative Properties

Solid StateClassification of Solids by Type of Attraction between UnitsCrystalline solids; crystal lattices and unit cellsStructures of some crystalline solidsDetermining the Crystal Structure by X-ray Diffraction

Intermolecular Forces: Phases of Matter

Phase Transitions• Melting: change of a solid to a

liquid.

• Freezing: change a liquid to a solid.

• Vaporization: change of a solid or liquid to a gas. Change of solid to vapor often called Sublimation.

• Condensation: change of a gas to a liquid or solid. Change of a gas to a solid often called Deposition.

H2O(s) H2O(l)

H2O(l) H2O(s)

H2O(l) H2O(g)

H2O(s) H2O(g)

H2O(g) H2O(l)

H2O(g) H2O(s)

Phases of Matter / Phases of Matter / Intermolecular ForcesIntermolecular Forces

Phase ChangesPhase Changes

QUESTION

ANSWER

B) crystallization

As a substance crystallizes, generally from a liquid, but a gaseous starting point is possible, the molecules, atoms, or ions lose kinetic energy to allow for bonding. This kinetic energy is emitted as heat.

Bonds vs. Intermolecular Bonds vs. Intermolecular ForcesForces

16 kJ/mol

431 kJ/mol

(150 - 1000 kJ/mol) (Ionic bond 700-4,000 kJ/mol)

Ion-Dipole Forces (40-600 kJ/mol)• Interaction between an ion and a dipole (e.g. NaOH and

water = 44 kJ/mol)• Strongest of all intermolecular forces.

Intermolecular ForcesIntermolecular Forces

Dipole-Dipole Forces

(permanent dipoles)

Intermolecular ForcesIntermolecular Forces

5-25 kJ/mol

Dipole-Dipole Forces

Intermolecular ForcesIntermolecular Forces

London or Dispersion Forces• An instantaneous dipole can induce another dipole in an

adjacent molecule (or atom).• The forces between instantaneous dipoles are called

London or Dispersion forces ( 0.05-40 kJ/mol).

Intermolecular ForcesIntermolecular Forces

London Dispersion Forces

Intermolecular ForcesIntermolecular Forces

Which has the higherattractive force?

London Dispersion Forces

Intermolecular ForcesIntermolecular Forces

Gecko: toe, setae, spatulae6000x Magnification

http://micro.magnet.fsu.edu/primer/java/electronmicroscopy/magnify1/index.html

Geim, Nature Materials (2003) Glue-free Adhesive100 x 10 6 hairs/cm2

Full et. al., Nature (2000)5,000 setae / mm2

600x frictional force; 10-7 Newtons per seta

Boiling Points &

Hydrogen Bonding

Boiling Points &

Hydrogen Bonding

Hydrogen Bonding

• Hydrogen bonds, a unique dipole-dipole (10-40 kJ/mol).

Which pure substances will not form hydrogen bonds?

I) CH3CH2OH II) CH3OCH3

III) H3C−NH−CH3 IV) CH3F

A) I and II B) I and III C) II and III D) II and IV  

QUESTION

Which pure substances will not form hydrogen bonds?

I) CH3CH2OH II) CH3OCH3

III) H3C−NH−CH3 IV) CH3F

A) I and II B) I and III C) II and III D) II and IV  

ANSWER

Hydrogen Bonding

Intermolecular ForcesIntermolecular Forces

DNA: Size, Shape & Self Assemblyhttp://www.umass.edu/microbio/chime/beta/pe_alpha/atlas/atlas.htm

Views & Algorithms

10.85 Å10.85 Å

Intermolecular ForcesIntermolecular Forces

Protein Shape: Forces, Bonds, Self Assembly,Folding

10-40kJ/mol

700-4,000kJ/mol

150-1000kJ/mol

0.05-40kJ/mol

Ion-dipole(Dissolving)40-600kJ/mol

Predict which liquid will have the strongest intermolecular forces of attraction (neglect the small differences in molar masses).

A) CH3COCH2CH2CH3 (molar mass = 86 g/mol)

B) CH3CH2CH2CH2CH2OH (molar mass = 88 g/mol)  

C) CH3CH2CH2CH2CH2CH3 (molar mass = 86 g/mol)

D) HOH2C−CH=CH−CH2OH (molar mass = 88 g/mol)

QUESTION

Predict which liquid will have the strongest intermolecular forces of attraction (neglect the small differences in molar masses).

A) CH3COCH2CH2CH3 (molar mass = 86 g/mol)

B) CH3CH2CH2CH2CH2OH (molar mass = 88 g/mol)  

C) CH3CH2CH2CH2CH2CH3 (molar mass = 86 g/mol)

D) HOH2C−CH=CH−CH2OH (molar mass = 88 g/mol)

ANSWER

Vapor Pressure on the Molecular Level

Vapor PressureVapor Pressure

Would water have a higher or lower vapor pressure @ the same temperature? (bp H2O > CH3CH2OH;

bp = oC when Vapor Pressure = Atmospheric Pressure)

Explaining Vapor Pressure on a Molecular Level

Vapor PressureVapor Pressure

Volatility, Vapor Pressure, and Temperature

Vapor PressureVapor Pressure

Solid Liquid Gas

Vapor PressureVapor Pressure

QUESTION

ANSWER

E) The vapor pressure of a liquid.

Molecules at the surface of a liquid will be held tighter by stronger intermolecular forces, making it more difficult for them to escape into the vapor phase.

Temperature & Vapor Pressure• The boiling point (b.p.) of

a pure liquid is the temperature at which the vapor pressure above the liquid equals the external pressure.

• Could water boil @ 0oC?

Temperature Dependence of Vapor Pressures

• The vapor pressure above the liquid varies exponentially with changes in the temperature.

• The Clausius-Clapeyron equation shows how the vapor pressure and temperature are related.

€

lnP = −ΔHvap

R×

1

T+ C (R = 8.314 J K−1 mol−1)

Clausius – Clapeyron Equation

• A straight line plot results when ln P vs. 1/T is plotted and has a slope of Hvap/R.

• Clausius – Clapeyron equation is true for any two pairs of points.

€

lnP2

P1

=ΔHvap

R×

1

T1

−1

T2

⎛

⎝ ⎜

⎞

⎠ ⎟

QUESTION

ANSWER

3 2– – 2 3

D) diethyl ether, CH CH O CH CH

Diethyl ether boils first as the temperature increases, leading one to believe that its vapor pressure at any temperature is also the highest of the given group of compounds.

Heating Curve

http://chemconnections.org/general/movies/HeatingCurves.swf

Energy (Heat) and Phase Changes

• Heat of vaporization: heat needed for the vaporization of a liquid.

H2O(l) H2O(g) H = 40.7 kJ/mol

• Heat of fusion: heat needed for the melting of a solid.

H2O(s) H2O(l) H = 6.01 kJ/mol

• Temperature does not change during the change from one phase to another.

50.0 g of H2O(s) and 50.0 g of H2O(l) were mixed together at 0°C. Determine the heat required to heat this mixture to 100.0°C and evaporate half of the water.

Phases of Matter / Phases Diagrams Solids (Crystals) & Solutions

Colligative Properties

Dr. Ron Rusay

Intermolecular Forces II

Phase Diagrams

• Graph of pressure-temperature relationship; describes when 1,2,3 or more phases are present and/or in equilibrium with each other.

• Lines indicate equilibrium state between two phases.

• Triple point- Temp. and press. where all three phases co-exist in equilibrium.

• Critical temp.- Temp. where substance must always be gas, no matter what pressure. • Critical pressure- vapor

pressure at critical temp.• Critical point- system is at its

critical pressure and temp.

Phase DiagramsPhase Diagrams

Phase DiagramsPhase Diagrams

The Phase Diagrams of H2O and CO2

Phase DiagramsPhase Diagrams

http://www.youtube.com/watch?v=OQPD4YBgeT8&feature=relatedhttp://www.youtube.com/watch?v=UVaPw9XzQ3g&feature=related

http://www.youtube.com/watch?v=c2ZRwwHfC2c

Published by AAAS

S. H. Oh et al., Science 330, 489-493 (2010)

Oscillatory Vapor-Liquid-Solid growth of sapphire nanowires (α-Al2O3)

660°C, Pressure = 10–6 Pa

Critical Temperature and Pressure

Phase ChangesPhase Changes

SolutionsSolutions

Bonus:Explain how a 50:50 molar solution of molten potassium & sodium nitrates could be used to store solar energy.

Freezing Point: 238°CMelting Point: 221°CHeat of Fusion: 161 kJ/kg

Archimedes’ Mirrors

SolutionsSolutions

Bonus:Explain how a 50:50 molar solution of molten potassium & sodium nitrates could be used to store solar energy.

Freezing Point: 238°CMelting Point: 221°CHeat of Fusion: 161 kJ/kg

http://www.archimedesolarenergy.com/video3.htm

SolanaSolana

$ 2 billion 3 years2,200,000 m2

2,700 mirrors

280 MegaWatts70,000 homes

- 475,000 MT CO2 Equivalent

http://www.youtube.com/watch/?v=G1hdoWk17wU

Bonus:The heat from a solution of molten potassium & sodium nitrates is used to store the energy, which turns a turbine in 6 hrs of darkness/ day.

SolutionsSolutions

QUESTION

ANSWER

B) decreases over time.

The concentration of the solution increases as the water evaporates. The higher the concentration of salt, the lower the vapor pressure.

Concentration Gradients:

Diffusion

Factors Affecting SolubilityFactors Affecting Solubility

• Movement of molecules from an area of high concentration to an area of lower concentration.

• Factors that affect the rate of diffusion: size of molecules, size of pores in membrane, temperature, pressure, and concentration.

Osmosis• Osmosis is the movement of solvent across a semi-

permeable membrane• Initially the concentration of solute is very high, but

over time, the solvent moves across the semi-permeable membrane and dilutes the particles.

Osmosis – A Special kind of Diffusion

Diffusion of water across a selectively permeable membrane (a barrier that allows some substances to pass but not others). The cell membrane is such a barrier.

Small molecules pass through – eg. water

Large molecules can’t pass through – eg. proteins and complex carbohydrates

https://www.youtube.com/watch?v=sdiJtDRJQEc

Over time molecules move across the membrane until the concentration of solute is equal on both sides. This type of solution is called ISOTONIC.

Pressure Effects

Factors Affecting SolubilityFactors Affecting Solubility

gg kPS =

If Sg is the solubility of a gas, k is a constant, and Pg is the partial pressure of a gas, then Henry’s Law gives:

QUESTIONA minimum of 1.3 10–4 M O2 must be maintained in freshwater

supplies to sustain aquatic life. In the mountains of Montana, the partial pressure of O2 may drop to 0.15 atm. What is the water

concentration of O2 there? Henry’s constant for O2 = 1.3 10–3

mol/L-atm. At the lower elevations at the base of those mountains, would more or less O2 be dissolved in water?

•M = 2.0 10–4; more dissolved•M = 8.7 10–4; more dissolved•M = 2.0 10–4; less dissolved•M = 8.7 10–4; less dissolved

ANSWERA) provides the correct M and the correct change in concentration. Henry’s Law relates pressure of a gas over a solution to the concentration of the gas in the solution: C = k P. At lower altitudes, the partial pressure of O2 would be higher, thus more O2 would dissolve. The huge fishing population of Montana is very appreciative of Henry’s Law.

Phase Diagrams for Pure Water (Red) and for an Aqueous Solution Containing a Nonvolatile

Solute (Blues)

Sugar Dissolved in Water to Make Candy Causes the Boiling Point to be Elevated

Spreading Salt

on a Highway

The Addition of Antifreeze Lowers the Freezing Point of Water in a Car's Radiator

• Colligative properties depend on quantity and type of solute/solvent molecules. (E.g. freezing point depression and melting point elevation.)

Lowering Vapor Pressure• Non-volatile solvents reduce the ability of the surface

solvent molecules to escape the liquid.• Therefore, vapor pressure is lowered.• The amount of vapor pressure lowering depends on the

amount of solute.

Colligative PropertiesColligative Properties

Lowering Vapor Pressure

• Raoult’s Law: PA is the vapor pressure with solute, PA is the vapor pressure without solvent, and A is the mole fraction of A, then

• Recall Dalton’s Law:

Colligative PropertiesColligative Properties

€

PA = ΧA P°A

€

PA = ΧA Ptotal

QUESTION

ANSWER

C) 0.800

Remember to convert grams to moles before attempting to find the mole fraction.

molality and Molarity

• Molality relates to colligative properties.• Converting between molarity (M) and molality (m)

requires density.• Therefore Molarity and molality are most often not equal

ConcentrationConcentration

solvent of kgsolute moles

Molality, =m

QUESTION

ANSWER

A) 5.47 m

Using the density, the mass of the solution is found. Don’t forget that molality has units of kg of solvent and the mass of the solute must be subtracted from the calculated mass of solution.

Molal Boiling-Point Elevation Constants (Kb) and Freezing-Point Depression Constants (Kf)

for Several Solvents

QUESTIONHousehold bleach is an aqueous solution of sodium hypochlorite. If 5.25 g of NaOCl (molar mass = 74.5 g/mol) were placed in 94.75 g of water, what would you calculate as the molality? The density of the solution is slightly greater than water. Would the molarity of the solution be greater, less or the same as the molality?

A.0.0705 m; M would be greaterB.0.705 m; M would be the sameC.0.744 m; M would be greaterD.0.744 m; M would be less

ANSWERD) provides the correct answer to both parts of the question. The molality involves moles/kg of water, so the given mass of solute can be converted to moles of solute and then divided by0.09475 kg to obtain molality. The molarity of the solution will be greater than the molality because the density of the solution shows that one milliliter of solution has a mass greater than one. So one liter of solution will contain more mass of solute than would be found mixed with one kilogram of water.

QUESTIONSuppose you want to keep the water in your car cooling system from freezing during a cold Alaska winter night. If you added 5.00 kg of ethylene glycol (C2H4(OH)2 MM = 62.0 g/mol) to

5.50 kg of water, what would be the freezing temperature of the coolant/water mixture in your automobile?

k f.p. H2O = –1.86°C kg/ mol

•–0.0367°C•–7.90°C•–14.7°C•–27.3°C

ANSWERD) -17.14 oFprovides the correct, although very cold, answer for that Alaska night. The molality of ethylene glycol must be calculated from the mass (in grams) and molar mass. This is then multiplied by the freezing point depression constant for the solvent to obtain the drop in freezing point. Since water normally freezes at zero degrees Celsius, the change is the actual new freezing point.

Atomic Solid / Ionic Solid / Molecular Solid

Structure of SolidsTypes of solids:

– Crystalline – a well defined arrangement of atoms; this arrangement is often seen on a macroscopic level.

• Ionic solids – ionic bonds hold the solids in a regular three dimensional arrangement. Eg. “Galena”, lead sulfide ore

http://en.wikipedia.org/wiki/Crystal_radiohttp://www.crystalradio.net/

• Molecular solid – solids like ice that are held together by intermolecular forces.

• Covalent network – a solid consists of atoms held together in large networks or chains by covalent networks. Eg. Diamond & graphite

• Metallic – similar to covalent network except with metals. Provides high conductivity.

– Amorphous – atoms are randomly arranged. No order exists in the solid. Eg. Glass, gels, thin films

Structure of SolidsStructure of Solids

Closest Packing Arrangement of Uniform Spheres

Arrays of atoms act as if they are spheres. Two or more layers produce a 3-D structure.

Close Packed: The Red Sphere has 12 Nearest Neighbors

Closest Packed Structure

• Crystals are made up regular arrays – the smallest repeating array of atoms is called the unit cell.

• There are 14 different unit cells that are observed which vary in terms of the angles between atoms some are 90°, but others are not.

Unit CellsUnit Cells

• Length of sides a, b, and c as well as angles vary to give most of the unit cells.

Unit CellsUnit Cells

Consider an interior atom in the simple cubic crystal lattice. What is the maximum number of unit cells that share this atom in the three-dimensional crystal lattice?

A) 2 B) 4 C) 6 D) 8

QUESTION

Cubic Hexoctahedral cF8, space group Fm3m, No. 225

Consider an interior atom in the simple cubic crystal lattice. What is the maximum number of unit cells that share this atom in the three-dimensional crystal lattice?

A) 2 B) 4 C) 6 D) 8

ANSWER

• Simple-cubic• Body-centered cubic• Face-centered cubic

Unit CellsUnit Cells

The number of atoms per unit cell in the body-centered cubic lattice is

A) 1 B) 2 C) 3 D) 4

QUESTION

The number of atoms per unit cell in the body-centered cubic lattice is

A) 1 B) 2 C) 3 D) 4

ANSWER

• Face Centered Cubic structure has a-b-c-a-b-c stacking. It takes three layers to establish the repeating pattern and has 4 atoms per unit cell and the coordination number is 12.

Unit CellsUnit Cells

The Net Number of Spheres in a Face-Centered Cubic Unit Cell

• Simple-cubic shared atoms are located only at each of the corners. 1 atom per unit cell.

• Body-centered cubic 1 atom in center and the corner atoms give a net of 2 atoms per unit cell.

• Face-centered cubic corner atoms plus half-atoms in each face give 4 atoms per unit cell.

Unit CellsUnit Cells

Unit CellsUnit Cells

Galena, lead sulfideCubic Hexoctahedral cF8,

space group Fm3m, No. 225

Can you hear anything?

Crystals for the ClassroomBridging the realms of the macro and atomic/nano scale

http://crystals.llnl.gov

Connecting: Science, Technology, Engineering and Mathematics (STEM)

The story of NIF ( The National Ignition Facility) http://crystals.llnl.gov/nif-kdp-frameset.html

Crystals for the ClassroomBridging the realms of the macro and atomic/nano scale

http://crystals.llnl.gov

Crystals for the ClassroomBridging the realms of the macro and atomic/nano scale

http://crystals.llnl.gov

Time lapsed KDP Growth

Simulation: Fusion

Crystals for the ClassroomBridging the realms of the macro and atomic/nano scale

http://crystals.llnl.gov

X-ray Crystallographyhttp://info.bio.cmu.edu/courses/03231/ProtStruc/ProtStruc.htm

Rosalind Franklin’s Photo 51

http://molvis.sdsc.edu/pdb/dna_b_form.pdb

46 Å

12 base sequence

(1953)