1 / 21

Warm-up

Warm-up. Complete the exercise Don’t look on the back of the sheet, this is not graded, try it yourself for practice…it is called a learning exercise. Draw Lewis structure and determine which molecule is most polar.

tuwa
Download Presentation

Warm-up

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Warm-up • Complete the exercise • Don’t look on the back of the sheet, this is not graded, try it yourself for practice…it is called a learning exercise. • Draw Lewis structure and determine which molecule is most polar. • In the lesson today we will discuss how the polarity of a molecule determines how it bonds with other molecules. These intermolecular forces account for many properties of a compound.

  2. Liquids Properties of liquids are similar to solids’, and way different from gas properties density compressibilities enthalpy changes attractive forces How does this relate to the KMT?

  3. Intermolecular Forces • Low density • Highly compressible • Fill container • Gases • Solids • High density • Slightly compressible • Rigid (keeps its shape)

  4. Intermolecular Forces • Intermolecular forces – occur between molecules • Intramolecular forces – occur inside the molecules

  5. Introduction to IAF • http://www.brightstorm.com/science/chemistry/chemical-bonds/intermolecular-forces • Checkout Brightstorm.com - good stuff

  6. Intermolecular Attractive Forces between molecules (liquids & solids) • Forces that act between molecules (or atoms) keeping them in one phase, liquid • A sample of a liquid will remain in that phase until IAFs are overcome, usually due to an increase in temperature or decrease inpressure • For IAFs, you focus on many molecules in a sample, once you have determined if you have polar or non-polar bonds between the atoms that make up the molecules • Remember, bond determination occurs due to electronegativity differences between two atoms (0.0 – 0.4 – non-polar covalent bond, 0.4 – 1.9 polar covalent bond, > 1.9 – ionic bonds) • IAF determination occurs when you look at the interaction of molecules.

  7. TYPES of IAFs • dipole-dipole • Occurs between 2 polar molecules • Polar molecules have a partial negative end (pole) δ+ δ- H-----F • F is more negative, therefore hogs () the electrons in the bond • Many H---F molecules attracted to each other • A strong force • The molecules hold onto each other, won’t allow them to escape to gas phase (evaporate, boil)

  8. 2. Hydrogen Bonding • A force between molecules • NOT a bond between atoms • A special type of dipole-dipole • Between H and N, O, or F • The STRONGEST IAF!!! • Molecules with hydrogen bonding have the highest melting and boiling point of covalent, molecular compounds --- why? δ- O Each H—O bond is polar Eneg difference is 1.4 Oxygen is the hog  δ+ H δ+ H

  9. 3. Ion-dipole forces • Between ion and greatly polar molecule, like • Accounts for solubility • Ionics in H20 – solutions • Na—Cl soluble? Yes, why? • Cl ion is attracted to δ+ H in H20 + Na ion is attracted to δ- O in H20 • If the attraction is strong enough, the compound will be soluble. Is PbSO4 soluble?

  10. 4. London dispersion forces • Also called Van der Waal’s forces • Among non-polar molecules • Weakest IAF • Minimal attraction • H2, Cl2, CO2 at room temperature are gases, overcome IAFs

  11. London forces Induced dipole: Instantaneous dipole: Eventually electrons are situated so that tiny dipoles form A dipole forms in one atom or molecule, inducing a dipole in the other

  12. London Dispersion Forces • Van der Waals Forces • Forces that arise when a temporary dipole in a non-polar molecule induces a dipole in an adjacent non-polar molecule d+ d- d+ d-

  13. 0bserve Intermolecular Forces • Follow instruction carefully! • Place 3 drops of water carefully on the foil. Observe how the drops bead together • Place 3 drops of Witch Hazel on the foil. Observe. • Place 3 drops of 70% isopropyl alcohol on the foil. Observe.

  14. Likes Dissolve Likes • Observe- • Oil mixed with water • Oil mixed with isopropyl alcohol • Alcohol mixed with water

  15. Introduction to IAF • http://www.brightstorm.com/science/chemistry/chemical-bonds/intermolecular-forces • Checkout Brightstorm.com - good stuff

  16. Van der Waals Forces and Animal Adhesion www.whyfiles.com http://www.gotpetsonline.com/pictures-gallery/reptile-pictures-breeders-babies/tokay-gecko-pictures-breeders-babies/pictures/tokay-gecko-0005.jpg upload.wikimedia.org

  17. 1 cm 1 mm 100 m The Nanoworld 10 m 0.1 nm 1-10 nm 1 m http://microcosm.web.cern.ch

  18. Phase Diagram of Water

  19. Phase Diagram Carbon Dioxide

More Related