• April 21st, 2016

Chemistry

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Many of the materials we use every day, like starch, are made up of molecules called POLYMERS. POLY means many and MER means unit. The units in these chains are very long.

Part 1: Polymer Demonstration

Go to the following webpage: http://www.chem.leeds.ac.uk/delights/texts/expt_31.html If you are not automatically brought to it, select Experiment #31. View the demonstration (click on “animation” or click on each slide) and read the information provided. Answer the questions below.

Questions:
1.Briefly explain what the demonstration is showing.
2.What kind of polymerization is this showing? How do you know?
3.How many seconds did the process take in the demonstration?
4.How long after the reaction is the material safe to be handled?
5.Describe the foam that is produced in this demonstration.
6.What are some properties of the product made in the demonstration?
7.Sometimes this reaction is advised to take place in an ice bath (especially if large quantities are produced). Explain why.

Part 2: Household Polymer Experiment
1.Place 10 mL of nail polish remover (or another household product that contains

acetone) in a beaker and obtain ~15 packing peanuts (you may need more). Observe

the solutions and peanuts carefully and record their properties.
2.Stirring continuously, add packing peanuts one at a time to the acetone until no more

peanuts will dissolve. Describe what happened.
3.Using gloves, remove the polymer to a paper towel. Avoid getting your polymer on

the table, floor or your clothes.

Questions:

8. What are the properties of this new polymer compared with polystyrene?

9. Observe and describe the following properties:

“Stretchiness” (Pull the polymer slowly. Pull the polymer quickly.)

“Bounciness” (See if you can bounce a piece of the polymer off a paper towel)

“Stickiness” (See if a piece of polymer will be flattened or stick to a surface as you press down on it.)

Part 3: Creating Polymer Slime

Because the units in polymer chains are so long, they interfere with the ability of the solution to flow. Viscosity is a physical property of liquids that describes how they flow. Honey and corn syrup are described as having high viscosities because they flow more slowly than water.

Procedure
1.Pour 1 cup cornstarch into a bowl or beaker.
2.Continue to add a small amount of water until the solution begins to thicken. Stir carefully! Don’t fight the viscosity of the slime.
3.Pour some of the slime into the pie pan. Try to cut it as you pour. Slap the top of the slime in the pie pan.

Questions:

10. Describe what you observe throughout the entire procedure above.
11. Pour some slime into your hands and roll it into a ball. Does the ball keep its shape?
12. Make a “slime snake” and pull it apart quickly. What happens?
13. Write your name in the slime. Describe its appearance.

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