CHAPTER 13 LIQUIDS & SOLIDS CHM 130 GCC

13.1 Properties of Liquids Liquids take the shape of their container, but have a constant volume. Different liquids flow at different rates. (Viscosity) Liquids are not compressible since the atoms/molecules are close together. Liquids have much higher densities than gases. Soluble liquids will mix uniformly together.

13.2 IMF BONDS hold atoms together within a single molecule. (Polar and nonpolar covalent bonds) Review polar and nonpolar bonds and molecules INTERMOLECULAR FORCES (IMF) hold molecules together in liquids and solids. IMF are always weaker than bonds!

Bonds vs IMF In one HCl molecule what holds the H atom to the Cl atom is a polar covalent bond. H-Cl In a sample with thousands of HCl molecules what holds them together is IMF. H-Cl H-Cl

INTERMOLECULAR FORCES 1) Dispersion (London) Forces 2) Dipole-Dipole Forces 3) Hydrogen Bond Forces H bond forces is NOT a bond!!!

Dispersion (London) Force Temporary attraction between nonpolar molecules or atoms that form when two of them get real close. Electrons get pushed to one side so results in a temporary partial negative charge (d-) that disappears when the molecules separate. Often seen in gases since very little attraction between nonpolar molecules – thus they are not close together but far apart (gas)!!! Bigger molecules, more electrons, more London Force.

Two Nonpolar Molecules

Dipole – Dipole forces Exists between polar molecules. (have partial d+ and d– ends) The partial d+ end of one molecule is attracted to the partial d- end of a second molecule (opposites attract). H Cl d - d + d - d +

Dipole-Dipole Forces Stronger than London forces. Must be POLAR molecules.

Hydrogen Bonding Force An especially strong dipole force between molecules containing the very polar H-F, H-O or H-N bonds. The d+ H end of one molecule is attracted to the d - N/O/F end of a second molecule.

H Bond Force Strongest type of IMF, yet still much weaker than a bond.

Indicate the strongest type of IMF between these molecules: Polar or Nonpolar? Strongest Intermolecular Force CO2 PF3 HF CH4 nonpolar London polar Dipole - Dipole polar H Bond Force nonpolar London

Bonds vs Forces Bonds Forces Ionic bond (holds metal/nonmetal ions together) Polar Covalent Bond (e- shared unequally between nonmetal atoms) Nonpolar Covalent Bond (e- shared equally) Forces London (nonpolar molecules) Dipole Dipole (polar molecules) H bond Force (H bonded to NOF)

Coulomb’s Law Review Opposite charges attract according to Coulomb’s Law The electrostatic attraction between two charges is proportional to the charge magnitude (q) and inversely proportional to the distance (r) squared. F = ke(q1q2 / r2) Larger charge means stronger attraction! Ionic bonds very strong cause charges are complete +1, +2, +3 charges. Like in NaCl. Dipole dipole IMF much weaker cause charges are much less than +1. Remember polar bonds are partially d+ and d -.

Choose the bond or IMF described for each below: What holds these together??? What holds the atoms together in one ammonia NH3 molecule? What is holding the H and O atoms together in water? What is holding three HCl molecules together? What is holding the ions together in salt NaCl. What is holding four H2O molecules together. What holds nitrogen gas molecules to each other? What is holding the O’s together in an oxygen gas molecule? What is holding two ammonia molecules together? Answers on Next Slide

Choose the bond or IMF described for each below: What holds these together??? Polar covalent bonds What holds the atoms together in one ammonia, NH3, molecule? What is holding the H and O atoms together in water? Dipole Dipole forces What is holding three HCl molecules together? Ionic bonds What is holding the ions together in salt NaCl. H bonding forces What is holding four H2O molecules together. London forces What holds nitrogen gas molecules to each other? Nonpolar covalent bonds What is holding the O’s together in an oxygen gas molecule? What is holding two ammonia molecules together?

13.3 Vapor Pressure (VP) At the surface of a liquid some molecules have enough kinetic energy to break the attractive forces (IMF) with neighboring molecules. They escape from the liquid and go into the gas state. If no lid, they float away with air molecules. If there is a lid, a pressure develops.

Which has weaker IMF? Higher VP? Vapor Pressure is the pressure exerted by gas molecules above a liquid in a closed container. Stronger IMF  higher or lower VP ??? Lower. Stronger attractions mean less likely to break away from surface and go into gas state (so less gas so less pressure) Which has weaker IMF? Higher VP? A A

Balloons are attached to flasks containing water and ether Balloons are attached to flasks containing water and ether. Which has stronger IMF? Higher VP? Water has stronger IMF and it stays together as liquid. Ether has low IMF, molecules break away into gas filling balloon, so it has higher VP.

Boiling Point (bp) Temperature where liquid changes to gas. Stronger IMF = higher or lower bp ?? Higher Strong IMF means molecules held tightly together so more energy is required to pull them apart so need higher temp.

Surface Tension Surface molecules hold on to each other, this is why liquids make drops / beads. Stronger IMF = high or low surface tension? High – stronger IMF means molecules are attracted so molecules stay together with more surface tension.

Surface Tension Which drop of liquid has higher IMF & surface tension? A, because molecules held together and did not spread out very much

Higher because molecules held together so flow is hindered and slow. VISCOSITY The resistance of a liquid to flow. Oil flows slowly  high viscosity Vodka flows rapidly  low viscosity Stronger IMF  higher or lower viscosity ??? Higher because molecules held together so flow is hindered and slow.

Let’s compare ammonia and fluorine. First what IMF do they have? NH3 has H bonding force, F2 gas has London force Questions Which has stronger IMF? Which has the lower bp? Which is polar? Which has higher VP? Which is least viscous (if liquid)? Which has more surface tension? Ammonia Fluorine

Fill in the blanks with increase or decrease As IMF increase: Viscosity ____________ Bp ___________ Surface tension ___________ Vapor pressure ___________ increases increases increases decreases

13.4 Properties of Solids Solids have a fixed shape and volume. Solids are crystalline or noncrystalline. Solids are not compressible - particles are close together. Most solids have a slightly higher density than their liquid state. Solids sink in their liquid. Ice is an important exception since ice is actually less dense than water. Ice floats in water. Solids do not mix by diffusion or osmosis.

13.5 Crystalline solids Glucose Solid arranged in a specific order. Crystalline solids have regular geometric shapes / patterns like hexagonal Quartz Cu Emerald

SOLIDS Type Particles mp & bp Other properties Ex. Ionic metal cations & nonmetal anions High hard, brittle, some soluble in water, conduct electricity when melted or dissolved in water KCl AgBr CaF2 MgCl2 Molecular nonmetal atoms or molecules Low usually insoluble in water, do not conduct electricity S8 Dry ice Metallic metal atoms surrounded by "sea of electrons" Varies malleable, ductile, insoluble in most liquid solvents, conduct electricity silver zinc

Ice Salt NaCl Copper

13.6 HEATING CURVE

HEATING CURVE gas l D g bp T (C) liquid s D l mp solid Heat Added g g g

13.7 Structure of Water H2O has a bent molecular geometry with a bond angle less than 109.5  Water has very polar O-H bonds: can dissolve many ionic compounds and mix with other polar substances Water has strong H bond Forces between molecules.

13.8 Properties of water Very polar, high IMF Low vapor pressure Unusually High bp & mp: bp=100C, mp=0C High surface tension Water expands as it freezes  Density of ice is less than density of liquid water ( really rare and odd) Figure: 13-11 Title: Bonding in a Water Molecule Caption: The arrangement of the electron pairs in a water molecule forms the four corners of a tetrahedron. Notes: The two hydrogen atoms are repelled slightly toward each other by the two nonbonding pairs. The bond angle is 104.5 .

For Fun Henry’s Law http://www.youtube.com/watch?v=8yU5y-cFXoo&feature=related Solubility of a gas in a liquid increases as P increases, and decreases as P decreases When you open soda can, you decrease the pressure, and some CO2 gas comes out of solution as bubbles (solubility decreased) The Bends http://www.youtube.com/watch?v=0ixYDJAYOYk

Self Test Page 382 Try 1-5, 11-13 Answers in Appendix J