HANDS-ON ACTIVITIES FOR CHEMISTRY STUDENTS
To help create a more favorable learning environment, I have created “hands-on” activities that can either be taught in addition to the old “ball and stick” chemical reactions model or replace this method all together. I developed these lessons while attending the Educators' Science and Mathematics Institute Series (ESMIS) at Michigan Technological University during June 24-28, 2002.
Learner Expectations (Desired results)
Students will be able to list and describe bond types.
Students will be able to draw structural formulas, including lone pairs, for single, double, and triple bonds.
Students will be able to draw molecular shapes based on the VSEPER theory.
Students will draw sketches of molecules using the correct geometric angles for bonds.
Introduction to Chemical Bonding
A chemical bond is a link between atoms that results from the mutual attraction of their nuclei for electrons. The main types of bonds that we will be covering are ionic bonds and covalent bonds. An ionic bond is the chemical bond that results from the electrostatic attraction between positive (cations) and negative (anions) ions. The ionic relationship is a “give and take” relationship. One ion donates or “gives” electrons, while the other ion receives or “takes” electrons.
A covalent bond is a chemical bond resulting from the sharing of electrons between two atoms. There are two main types of covalent bonds. The first being non-polar covalent bonds. These are bonds in which the bonding electrons are shared equally by the united atoms-with a balanced electrical charge. Polar covalent bonds are covalent bonds in which the united atoms have an unequal attraction for the shared electrons.
Because bonding is such a hard concept for students to grasp, I break it down even further by correlating the main types of bonds to divorce custody agreements. Ionic bonding would be like where a child lives with one parent and never sees the other parent. In this case, the parents do not share the child at all. Non-polar covalent bonding would be like when a child spends one week with one parent and the next week with the other. The child is shared equally with both parents. Polar covalent bonding would be like when the child spends most of the time with one parent, but every Wednesday and every other weekend with the other parent. The child is shared, but not shared equally.
How to tell what kind of bond we are dealing with…
Find the electronegativity for each element or ion in compound, (using electronegativity table provided, Figure 1-see attached).
Subtract the electronegativites (using absolute value).
If values are between
4.0-1.7---Ionic bond-50-100% ionic
1.7-0.3---Polar Covalent bond-5-50% ionic
0.3-0.0---Non-Polar Covalent-0-5% ionic
Why does chemical bonding occur?
Bonding occurs in order to lower the total potential energy of each atom or ion. Throughout nature, changes that decrease potential energy are favored.
Other Key Terms:
Octet rule-states that chemical compounds tend to form so that each atom, by gaining, losing, or sharing electrons, has an octet (8) of electrons in its highest occupied energy level, (otherwise known as the “outer shell”).
Unshared pair (lone pair)-is a pair of electrons that is not involved in bonding, but belongs solely to one atom.
VSEPR (valence-shell electron pair repulsion) theory-states that valence pairs (pairs available for bonding) are arranged as far from each other as possible. The repulsion force between electrons is what gives rise to the shape of molecules, (or degrees of angles between bonds).
Figure 2-see attached
Other covalent bond types
Single covalent bond
Ex) H Cl
Double covalent bond
Ex) C C
Ex) C = C
Triple covalent bond
Ex) N N
Ex) N = N
The following activity, I developed because I do not have enough “ball and stick” models to go around. Another positive point for the students is that they get to eat their creations once their sketches have been approved.
Each of the following activities is done in groups of 2-3 people.
“Hands On Activity #1”--Edible Bonding Lab-50 minutes
Purpose: to be able to visualize bonding, angles, multiple bonds, as well as the position of lone pairs in molecular formulas.
Materials: Large Marshmallows, small colored marshmallows, red-hot candies, gumdrops, and toothpicks
Compounds involved: H 2O-Water
Continued… N2-Diatomic Nitrogen
Make Water Molecule
Lone pair-red-hot candies
Make Ammonia molecule
Lone pair-red-hot candies
Make Methane molecule
Make Ethane Molecule
Lone Pairs-Red-hot candies
Make Diatomic Nitrogen Molecule
Lone Pairs-Red-hot candies
Make Formaldehyde Molecule
Red-hot candies if needed
***Remember to use more toothpicks if multiple bonds occur.
Results: Sketches of molecules including approximate bond angles.
Conclusion: What is the most electronegative atom in each case? Why is this important to know? How does electronegativity affect molecular shape? What did you learn from this lab? Any Problems?
“Hand's On Activity #2”-Molecular Yarn Art-90 minutes
Purpose: Students will explore molecular geometry while making yarn art projects.
Materials: Various colors of Yarn, Manila file folders, O-ring adhesive (found in plumbing supply), scissors, pencil, molecular formulas of various molecules (drawn on index cards and provided by teacher).
Obtain an index card of a molecule.
Sketch molecular shape on Manila file folder.
Use O-ring adhesive to fill in all areas with yarn patterns.**Elmer's glue can be substituted, but it is more frustrating for the student to work with.
See example-methane-CH4-Figure 3-see attached
**Note: You will have to provide a color key. On my example, Carbon is Blue and Hydrogen is Red. If a compound has three Hydrogen atoms, then all the H must be the same color, etc. etc.
Clean-up all work areas when finished. Please remember to wipe down your workstations!!!!
Conclusion: Please tell me about this bonding “art experience” in your own words. What did you learn? Any Problems?
Chemical bonding -Pretest/Posttest
Positively charged ions are called
b) Polyatomic ions
d) Monatomic ions.
A group of atoms united by covalent bonds is a(n)
Valence electrons are
Shared between atoms in molecule
Found in the energy level nearest the nucleus.
Shared between atoms in an ionic compound
Lost or gained by atoms in an ionic compound.
Which is an example of a polar molecule?
5. If a bond had an electronegativity difference of 0.8, what type of bond would this be categorized as?
Polar covalent bond
Non-polar covalent bond
LeMay, Eugene H. et al. Chemistry Connections to Our Changing World. Prentice Hall Publishing Company, 2000. Pp.224-243.
The real-world applications would be mostly that all chemical reactions are based on the placement of electrons. The elements in the periodic table have relationships with each other that cause bonding to occur. Every reaction is the exchange of electrons in one way or another. From all of these chemical bonds creates everything in life: our bodies, a cake rising as it bakes, products we buy…everything! I stress to students that this building block, bonding, is really the basis for most of the chemistry concepts we will study.
Performance Assessment Strategies
Evaluation of Lab Report: five points for every correct sketch, and ten points for conclusion.
Evaluation of Yarn Art Projects: color key, molecular shape, creativity, following directions.
Pre-test and Post Test
Science. Physical Science. Strand IV. Standard1. Key concepts: proton, neutron, electrons, charges.
Math. Geometry and Measurement. Strand II. Standard 1. Benchmark 4.Key concepts: shape as descriptive tool, relationships among shapes.
Math. Geometry and Measurement. Strand II. Standard 1. Benchmark 7. Key concepts: shape to describe physical world concepts