Name:_______________________

Honors

Chemistry

Lab name:______________

Mr. Grodski III

Experiment 16 - Intermolecular Attractions Lab - Making of Slime Introduction: There are basically four types of molecular attractions, dipole-dipole, H-bonding (a specific type of dipole-dipole force ), Van der Waals’ forces (London forces), and molecule-ion attractions (dissolving of a salt). These forces or bonds are responsible for the intermolecular attractions that affect vapor pressures and boiling points. The stronger the intermolecular force (attractions between molecules) the higher amount of energy that needs to be absorbed by the attracting molecules to overcome the attractive forces between, enabling them to separate into the gas phase. Based on the strength of intermolecular attractions, theoretical predictions can be made regarding boiling points. One type of molecular attractions, H-bonding, which is responsible for the relatively high boiling point of water as compared to other liquids, can also affect the physical properties of a polymer. In this lab, Poly (vinyl alcohol), a polymer (very large molecule that is like a chain of smaller, identical, molecules linked together) will be linked together with other chains of the same polymer by H-bonding . H-bonding will link the polymer strands when sodium tetraborate solution is added to the liquid polymer, Poly(vinyl alcohol) as shown:

Objectives:

Materials: 1. Poly(vinyl alcohol), 4 % solution. 3. Small paper cups and stir stick 2. Sodium borate, 4 % solution 4. Food color

Procedure: 1. Heat 100 ml of water to 70° C in a beaker and Slowly add 4 grams of poly(vinyl alcohol), constantly stirring, adding more only as it gets dissolved. 2. Make sure that the solution stays at 70° C by lowering the hot plate temp and/or periodic removal of the beaker from the hot plate. 3. Stir the solution till it is clear as determined by your instructor! 4. Pour your solution into a paper cup. 5. Add 16 ml of the sodium borate solution to each cup. If you want your polymer (slime) to have color add your food coloring this solution before you add it to the paper cups. 6. As the mixed solution begins to solidify, continue to stir. 7. When the gel has formed, rip the paper cup open and shape it with your hands!

Experiment 16 - Molecular Attractions Lab 1. What type of molecular attractions does this polymer utilize? What physical properties does this polymer exhibit that can help determine whether this is a strong force of attraction? (flexible, brittle, resilient) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ 3. When can Hydrogen Bonding occur and when is it the strongest? ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ 4. If Poly(vinyl alcohol) was non polar, what kind of attractions would occur between each strand of the polymer? How could the strength of this type of attraction be increased? How could the strength of this type of attraction be decreased? ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

5. Molecules of BrI under certain condition of pressure of temperature and pressure are in the liquid state. What type of attractions do these molecules have for one another? Are they as strong as water? How can we determine the relative strength of this attraction? ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

Name:_______________________

Honors

Chemistry

Lab name:______________

Mr. Grodski III

6. If LiBr is dissolved in water (hydrated) what kind of molecular attractions would it have? Can ions dissolve in nonpolar solvents? Why or why not? ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

7. Identify the type of intermolecular attraction between molecules or compounds or the type of intramolecular attactions (bonds) writing the bonds/attractions given to you in your word bank.

Fe(s)

Molecular Ion Attraction, London forces, Ionic Bond, Hydrogen Bonding, Dipole-Dipole interactions, Metallic Bonds

Experiment 16 - Molecular Attractions Lab 8. Please use a color code of your choice and color the bonds to identify the following intermolecular and intramolecular bonds in the polymer. Color -

Nonpolar covalent…………………..

-

Polar covalent………………………..

-

H-bonding……………………………

-

molecule –ion attraction……………..

-

London Forces........………………….