Happy Presidents Day!

Monday, Feb. 17 th : “A” Day Tuesday, Feb. 18 th : “B” Day Agenda  Finish section 6.1: “Covalent Bonds”  Lab Discussion/Write-up: “Nonmetal Reaction”  Lab: “Non-metal Reaction”  Homework: Pg. 198: #1-14 Completed lab will be due next time…

Polar Molecules Have Positive and Negative Ends  In a polar covalent bond, the ends of the bond have opposite partial charges because one of the atoms is “hogging” the electrons.  Dipole: a molecule or part of a molecule that contains both positively and negatively charged regions.  In a polar covalent bond, the shared pair of electrons are more likely to be found near the more electronegative atom.

Polar Molecules Have Positive and Negative Ends  The Greek symbol  (delta) means partial.  + is used to show a partial positive charge  – is used to show a partial negative charge  Example: H  + F  – is polar covalent Because the F atom has a partial negative charge, the electron pair is more likely to be found closer to the fluorine atom.

Polarity Is Related to Bond Strength  In general, the greater the electronegativity difference, the greater the polarity and the stronger the bond.

Polarity Is Related to Bond Strength Think of it this way:  You know that ionic bonds are stronger than covalent bonds.  The greater the difference in electronegativity, the closer the covalent bond comes to being like an ionic bond.

Electronegativity and Bond Types  Differences in electronegativity values provide one model that can tell you which type of bond two atoms will form.  Another general rule states: An ionic bond forms between a metal and a non-metal. A covalent bond forms between two non-metals.

Properties of Substances Depend on Bond Type  The type of bond that forms (metallic, ionic, or covalent) determines the physical and chemical properties of the substance.  Metallic bonds: good conductors in solid state because electrons are free to move around.  Ionic bonds: strong attraction between ions makes them solids with high melting/boiling points.  Covalent bonds: weaker attraction between molecules makes them gases/liquids at room temperature or solids with low melting/boiling points.

Your lab partner will be…

Lab: “Non-metal Reaction” Discussion  The active ingredient in household bleach is sodium hypochlorite, NaClO.  Sodium hypochlorite contains 1 metal atom (Na) and 2 non-metal atoms (Cl and O).  Oxygen gas supports combustion (burning) while chlorine gas does not.  In this lab, you will remove the oxygen from sodium hypochlorite in order to identify its presence.

Lab: “Non-metal Reaction” Changes to Materials List  Add the following to your list of materials:  Test tube holder Test tube rack Graduated cylinder (50 mL) Balance Formula for cobalt(II) chloride, CoCl 2

Lab: “Nonmetal Reaction” Lab Write-Up  Title  Purpose  Hypothesis  Materials  Procedure We will follow the procedure just as described Reflection Statement Remember to update your table of contents!

Lab: “Nonmetal Reaction” Discussion  On the back of your lab handout, below question #4, list 3 observations from the lab.  Instead of using a test tube holder like the picture shows, you can perform the test while the test tube is in the rack. This way you won’t have to hold it.  You and your lab partner need to work together to make this lab work. The match needs to be blown out just as your partner takes their thumb off the end of the test tube. Why?

Lab: “Nonmetal Reaction” Safety Items  Liquid laundry bleach, containing NaClO, and cobalt chloride, CoCl 2, can both be dangerous. Be careful when handling them and clean up any spills immediately.  DO NOT inhale any of the vapors coming out of the test tube or get too close to the test tube!  DO NOT let the pressure build up in the test tube!  Hair must be tied back because we will be using matches.  Be sure to wash your hands when you’re done.

Lab: “Nonmetal Reaction” Lab Questions  Use complete sentences to answer the 2 lab preview questions on the top of the lab handout as well as all of the lab conclusion questions.  Have fun and be safe!  Completed lab will be due next time…

Homework  Finish “Nonmetal Reaction” lab questions in COMPLETE SENTENCES.  Sec. 6.1 review, pg. 198: #1-14 Sec. 6.1 quiz next time…