Electronegativity and Polarity

After completing the entry task on slide 3 of the Lesson 43 PowerPoint, we visualized the concept of a “charged wand” and it’s effect on polar molecules using a balloon, electrons gently extracted from the hair of a student volunteer, and a burette filled with water.  Students observed water flowing straight through the burette at the beginning of the demonstration, and then saw how water was attracted to the “charged wand” when the balloon was placed close to the stream of water.  Students were challenged to explain the observation using their understanding from our work yesterday (models drawn in the class notes below).  Next, we watched the Bozeman Science video below about the polarity of water molecules to review, extend, and apply the learning from yesterday to real-world scenarios:

We then talked through the definitions of electronegativity and dipole, relating both concepts back to molecules of water and carbon dioxide (see class notes below).  Finally, students received copies of the Lesson 43 Worksheet and accompanying cartoon to work through.

Notes from class:

Lesson 43 Picture 1

Lesson 43 Picture 2

Keep Learning!

Looking for more challenge?  When drawn as vectors, dipole arrows allow scientists to calculate the magnitude and direction of the overall dipole of a molecule.  Using vector addition, dipole arrows explain why water is polar while carbon dioxide is non-polar.  Brush up on vectors and vector addition using the Gizmo simulations.  Ask for one or both copies of the Gizmo handouts and grow your brain!

Homework:

  • Read Lesson 43 in the textbook.  Login via the Sapling website and enter your username and password.
  • Write notes for Lesson 43 and work through the practice problems at the end of Lesson 43
  • Please ask questions about anything from Lesson 43 you do not yet fully understand.

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