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Chapter 2:1-9 The Chemical Basis of Life - Atoms and Reactions

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Biology Homework Chapter 2: Atoms and Molecules


Reading Preparation

Textbook assignment: Chapter 2: The Chemical Basis of Life, sections 1-9.

Study Notes

Web Lecture

Read the following weblecture before chat: The Chemical Basis of Life: Atoms

Take notes on any questions you have, and be prepared to discuss the lecture in chat.

Study Activity

Use the PhET molecular polarity simulation to explore how an atom's electronegativity (attraction for electrons) can change the nature of a chemical bond.

  • In the Two Atoms simulation,
    • Set the electronegativities for Atom A and Atom B equal (half way between less and more) and note there is no dipole.
    • Change Atom A to the least electronegative, and Atom B to the most. The dipole arrow should appear pointing toward the greatest electronegativity. What happens to the dipole arrow as you change these values?
    • Reset to neutral (central) electronegativities and display partial charges, then vary the electronegativity values again. What happens to the partial charges?
    • Reset and display the bond characters. What happens to the bond characters as you change the electronegativities?
    • Reset and display the electrostatic potential. What happens to the location and intensity of the positive and negative zones of the molecule as you change the electronegativity of each atom?
    • Reset and display the electron density (the likelihood that electrons are in a particular region). How does the location of electrons change when you change the electronegativity of an atom?
    • What happens when you put either of these two molecules in an electric field?
  • Play with the Three Atoms simulation in a similar way.
    • Think about the implications for a water molecule (B atom high electronegativity, A and C atoms low electronegativity, A and C at an angle to B).
    • Display the electric field and observe how it changes if you increase the electronegativity of one of the A or C atoms.
    • Set the conditions for carbon dioxide (low B electronegativity, high A and C electronegativity, A-B-C in a straight line) and observe the differences in electrical fields. Is the overall CO2 molecule polar the way the water molecule is?

Optional External Web site reading: The University of North Carolina Chemistry Department has a public tutorial on →atoms← that you may find interesting.

Chat Preparation Activities

Chapter Quiz

Lab Work

Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.