Modeling Molecules
Chemistry A Unit 4 Lab Portfolio
Introduction:
You can represent a molecule two-dimensionally, as a structural formula or electron dot structure. Although such models are useful in certain contexts, they do not accurately represent bond angles between atoms or shapes of molecules. In this activity, you will construct three-dimensional models of several molecules. You will use electron dot structures and structural formulas to inform how you construct the three-dimensional models.
Materials:
- Jelly beans, gum drops, gumballs, or other soft things with multiple colors
- Toothpicks or twist ties
- Colored pencils, markers, or crayons
Procedure:
1. Identify the chemical and structural formula and electron dot structures of the following molecules:
a. Water
b. Ammonia
c. Carbon Dioxide
d. Fluorine
e. Methane
f. Ethane
2. Write the formulas and draw the two-dimensional structure in the table below.
3. Chose one color candy to represent each atom of an element. Create a key that identifies each element. (example: red jelly bean = hydrogen, green jelly bean = oxygen)
4. Use the candy, toothpicks, and/or twist ties to construct a three-dimensional model of each of the molecules listed above.
5. Draw, as accurately as possible, each model in the table, using color as needed.
6. Answer the 5 Post-Lab questions in complete sentences, fully answering the question.
Data Table (12 points):
Molecule name / Chemical Formula / Electron dot structure / Structural formula / Drawing of modelWater
Ammonia
Carbon Dioxide
Fluorine
Methane
Ethane
Key:
Post-Lab Questions:
1. Compare the information provided by a molecule’s chemical formula to the information provided by its structural formula. (2 points)
2. Fluorine is a toxic, reactive gas. Which representation (structural formula, electron dot structure, or three-dimensional model) would you use to explain why fluorine is so reactive? Why? (2 points)
3. Identify the bond types between the carbon and the two oxygen atoms in the carbon dioxide molecule. (2 points)
4. Explain why it is difficult to accurately represent ammonia two-dimensionally. (2 points)
5. What is the major difference between the two-dimensional and three-dimensional models of ethane and methane? When might you choose to use a two-dimensional model rather than a three-dimensional model when representing one of the molecules? (2 points)
Grading Guidelines:
Accuracy of chemical formulas / All 6 chemical formulas are correct / Most (4-5) chemical formulas are correct / Some (2-3) chemical formulas are correct / Few (0-1) chemical formulas are correct
Accuracy of electron dot structures / All 6 electron dot structures are accurate / Most (4-5) electron dot structures are accurate / Some (2-3) electron dot structures are accurate / Few (0-1) electron dot structures are accurate
Accuracy of structural formulas / All 6 structural formulas are accurate / Most (4-5) structural formulas are accurate / Some (2-3) structural formulas are accurate / Few (0-1) structural formulas are accurate
Accuracy of model drawings / All 6 drawings are accurate / Most (4-5) drawings are accurate / Some (2-3) drawings are accurate / Few (0-1) drawings are accurate
Total score for the table /12
Answers to Post-Lab questions 1 – 5 are work two points each Total score for answer /10
Total Score /22