The Bond Energy Project


Background:

Chemical reactions occur around us everyday. Some absorb heat energy overall (endothermic) while others release energy (exothermic). With combustion reactions,heat is released, very exothermic in nature. What determines whether a reaction is endothermic or exothermic is based on the bond energies associated with the bonds breaking and the new bonds forming. Bonds breaking absorb energy to break, while bonds forming release energy when they form. The one that wins (is greater) determines the overall direction of heat energy flow.

Due Dates

1. Project Ideas (Reaction) due by Monday, March 30th.(5 pts)
2. Structural formulas due Wednesday, April 1st. (5 pts)
3. Bond Energy Table, Calculation, Explanation and Evaluation due by Friday, April 3rd. (25 pts)
NOTE: All steps (1,2,3) recorded on a GOOGLE DOC for final project

Directions:

IDEA (5 PTS)

1. Select a molecule (covalently bound) significant to everyday life. Alkanes, alkenes, alkynes, or any
molecules discussed in class are off limits. Some help can be found at:
http://en.wikipedia.org/wiki/List_of_organic_compounds but you are not limited to these.

2. Determine what elements formed this molecule. What are the elemental forms of these elements (i.e. how are they naturally found)?
A good way to determine this is to research the heats of formation of these elements. The form
with a heat of formation of zero is the natural form. For example the heat of formation of oxygen as O2 is zero. Ozone (O3) and atomic oxygen (O) are not.

3. Write a chemical reaction showing the formation of your molecule from its elements. Be sure
the reaction is balanced and shows whether the substances are solids (s), liquids (l) or gases (g).

4. Post your reaction on the wikispace (www.thechemspot.org) under the discussion tab of
this page. Use your name as the subject and record the balanced chemical equation in the box. In the box, also include the significance of the molecule. You have now claimed your project. I will be giving feedback for these on Monday. All reactions MUST be different. (My example is posted to show you how to record it).

5. Once you have your reaction you must complete the following:

STRUCTURES (5 PTS)

a. Draw structural formulas for each reactant and product. Be sure to include all bonds and
unshared pairs. Can be hand drawn with a photo taken or use a computer application like omnigraffle.

FINAL PROJECT (25 PTS)

b. Research the bond energies for each bond represented in your structures. Create a table
showing this.

c. Determine whether the reaction is endothermic or exothermic overall. Calculate the enthalpy
of the reaction and explain your results.

d. A sample for the formation of water from hydrogen and oxygen molecules can be found here.

6. Record all work on a google doc. (you may want to copy and paste these instructions).

7. Evaluate another student project. You should evaluate another student and your model must be evaluated for correctness.
Open this file, and follow the directions:

**REMEMBER: ALL WORK SHOULD BE COMPLETED BY MIDNIGHT, APRIL 3rd. Late Assignments will lose 5 pts/day.