Do Now: What keeps a solid or liquid together? Specifically, what keeps a sample of ______ together? Ice Carbon tetrachloride Sodium chloride Sodium Graphite

Liquids and solids Held together by forces among component molecules, atoms, or ions The strength of these forces will impact the properties of the solid/liquid

Types of forces include Intermolecular Forces Ionic Bond ( electrostatic force of attraction) Covalent Bond Metallic Bond London dispersion forces, dipole-dipole forces (hydrogen bonding)

Intermolecular Forces Dipole-Dipole forces – force of attraction between polar molecules –Hydrogen bonding – special case of dipole-dipole where H is bonded to N,O, or F London Dispersion Forces – force of attraction that exists in all molecules due to electric fluctuations that cause temporary dipoles. Temporary dipole induces a dipole in molecule next to it. Why these elements?

How do the intermolecular forces compare in terms of strength? In molecules of similar molar mass, Dipole-dipole is a stronger force of attraction than LDF In molecules of larger molar mass, LDF are likely to be more important than dipole-dipole forces

Do now 1.Determine the most important type of Intermolecular force between molecules of a)CO 2 b) Cl 2 c)HF d)NBr 3 1.Which molecule in each pair would exert greater intermolecular forces? Why? a) H 2 O or CH 4 b) CH 3 CH 3 or CH 3 CH 2 CH 2 CH 2 CH 2 CH 3

Describe the structures of Ice Carbon tetrachloride Sodium chloride Sodium Graphite

SubstanceAttractive Force Ionic (NaCl)Electrostatic Attractions Polar Molecular (Ice)LDF, Dipole-dipole Nonpolar molecular (Dry Ice) LDF Covalent Network (Carbon Allotropes) Covalent Bonds Metallic Ions with delocalized electrons Metallic Bonds

Ionic Solids – have strong Coulombic interactions between cation and anion. The smaller the ions, higher the charge, the stronger the Coulombic force of attraction, and the higher the melting point. Properties include… low vapor pressure brittle due to the repulsion of like charges caused when one layer slides across another layer. do not conduct electricity as solid, will when melted or dissolved as ions can move (Dissolving solid and observing solution’s ability to conduct electricity is a way to identify an ionic solid) tend not to dissolve in nonpolar solvents because the attractions among the ions are much stronger than the attractions among the separated ions and the nonpolar solvent molecules.

Metallic Solids – can be represented as positive kernels (or cores) consisting of the nucleus and inner electrons of each atom surrounded by a sea of mobile valence electrons. Properties include… good conductors of heat and electricity as electrons are free to move shiny wide range of melting points malleable, ductile, because deforming the solid does not change the environment immediately surrounding each metal core.

Interstitial alloys - form between atoms of different radius, where the smaller atoms fill the interstitial spaces between the larger atoms. (Steel is an example in which carbon occupies the interstices in iron.) Substitutional alloys - form between atoms of comparable radius, where one atom substitutes for the other in the lattice. (Brass is an example in which some copper atoms are substituted with a different element, usually zinc.) The density typically lies between those of the component metals, as with interstitial alloys, Alloys make the lattice more rigid, decreasing malleability and ductility than pure metals. Typically retain a sea of mobile electrons and so remain conducting. Alloy – mixture of metals

Covalent Network Crystal Carbon Graphite Diamond Buckminsterfullerene Solids that contain strong directional covalent bonds to form a solid that might be viewed as a “giant molecule”. Allotrope – form of an element differing in crystal or molecular structure

Diamond Hardest naturally occuring substance Used in industrial cutting implements Conductor or insulator?

Graphite Slippery (used as a lubricant) Conductor of electricity Pencil “lead”

Silicon – Covalent Network Crystal and Semiconductor can conduct electricity under some conditions but not others, making it a good medium for the control of electrical current. properties depend on the impurities, or dopants, added to it. In N-type doping, P or As added to the silicon in small quantities. Why? In P-type doping, B or Ga is the dopant. Why? Boron and gallium each have only three outer electrons. When mixed into the silicon lattice, they form "holes" in the lattice where a silicon electron has nothing to bond to. The absence of an electron creates the effect of a positive charge, hence the name P-type. Holes can conduct current as they accept an electron from a neighbor, moving the hole over a space.

A minute amount of either N-type or P- type doping turns a silicon crystal from a good insulator into a viable (but not great) conductor -- hence the name "semiconductor." N-type and P-type silicon are not that amazing by themselves; but when you put them together, you get some very interesting behavior at the junction. That's what happens in a diode.

What type of solid is glass?

Amorphous Material Substance that lacks order Does not have a sharply defined melting point As heated, gradually softens and flows Upon cooling, its flows more and more Examples:

DO NOW: Define each property below and determine how the strength of the IM forces will effect each. Also determine how changes in temperature will impact each. 1.Surface Tension 2.Viscosity 3.Vapor Pressure 4.Capillary Action 5.Melting/Boiling point  H vaporization, fusion -imbalance of forces at the surface of a liquid -is a measure of the resistance of a fluid to flow - pressure of vapor in equilibrium with its condensed phase (liquid or solid) What is volatility?

Capillary Action relies on cohesive and adhesive forces. Compare water and mercury. Assume the tubes are made of glass, SiO 2

What is the boiling point? What is effect of temperature on vapor pressure? Compare the IM forces of the three substances. Vapor Pressure Curves

Do Now: Solid Liquid Gas Name each phase change. Indicate if endothermic or exothermic process

Solid Liquid Gas Melting Evaporation/Boiling Sublimation Condensation Deposition Freezing

Water molecules at the surface overcome IM forces and escape into the vapor phase EVAPORATION (a surface phenomenon) Gaseous molecule will collide with the liquid surface and if kinetic energy sufficiently low it will be captured and return to liquid phase Dynamic Equilibrium Vapor Pressure

Boiling Boiling occurs in the volume of the liquid. Bubbles form and rise since the vapor pressure can overcome atmospheric pressure Boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the atmospheric pressure surrounding the liquid Normal Boiling Point the temperature at which a liquid's vapor pressure equals one atm

Phase Diagram 0ºC

Energy and changes of state

For water  H vap = 2260 J/g  H fus = 334 J/g c ice = 2.06 J/gºC c liquid water = J/gºC c steam = 2.02 J/gºC How much energy is required to convert 150. g of ice at -15ºC to steam at 110ºC?

Solids 1.Crystals – rigid body where constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. They can be classified by shape - Crystal systems (p414)

Unit cell is the simplest repeating unit that generates the crystal Each crystal system has specific unit cells Unit Cells Simple cubic Body-Centered cubic Face-Centered cubic

Simple Cubic Unit Cell How many atoms are encompassed in the unit cell? 1 atom/unit cell Relate the radius of atom to the length of the unit cell 2r = l

Face Centered Unit Cell How many atoms are encompassed in the unit cell? 4 atoms/unit cell Relate the radius of atom to the length of the unit cell l l 4r =  2 l

Body Centered Unit Cell How many atoms are encompassed in the unit cell? 2 atoms/unit cell Relate the radius of atom to the length of the unit cell l 2l 4r =  3 l

Metal atoms typically arranged in Face-centered Cubic Body-centered Cubic Hexagonal Closest Packed

FCC

Sodium chloride Green - chloride Blue - sodium Which type(s) of arrangements are the sodium and chloride ions occupying?

Determine Avogadro’s Number from… Iron has a density of 7.86 g/cm3 and its molar mass is g/mol. It crystallizes in a Body-centered Structure. By x-ray diffraction, the edge of the cubic cell is found to be 287 pm.