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ENGR 200: Materials of Engineering

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I. OBJECTIVES The purpose of this experiment is to reinforce student’s understanding of how the molecular shape of polymers and their size affect the mechanical behavior of polymers under tensile loading.


Polymers are organic in origin. For carbon chain polymers, the backbone of each chain is a string of carbon atoms. Within each molecule, the atoms are bound together by covalent interatomic bonds. The covalent bonds in each molecule are strong, but only weak hydrogen and Van der Waals bonds exist between molecules. The molecules in polymers are gigantic and because of their size they are often referred to as macromolecules. The mechanical properties of polymers are intricately related to the structural elements of the material. Polymers have interesting behaviors and special properties, partly because of their size. The large molecules become entangled with each other, much like a single strand of cooked spaghetti gets tangled up with other spaghetti strands in a bowl of pasta.

III. EXPERIMENTAL Materials and Apparatus

1. One packet of pasta (individual choice) 2. Salt (optional) 3. One cooking pot (available in your kitchen) 4. Fork (available in your kitchen) 5. Stove (available in your kitchen)

Figure 1. Materials: Pasta (Capellini)

Figure 2. Cooking pot Figure 3. Fork

Experimental Procedure

1. Each student will cook their own choice of spaghetti using their own cooking pot: the photographs of Materials and Equipment should be included in the report.

2. The number of servings is included in cooking instructions of each particular brand of pasta. Follow these instructions.

3. Each student will cook pasta for three different times to achieve different firmness of cooked pasta.

4. Place cooked pasta inside of a a bowl(s). Insert the fork deep inside the pasta, wind a certain amount of pasta on the fork and lift up the fork, allowing the pasta to do what it wants. Make observations on the manner in which the pasta behaves.

Cooking Directions

1. Bring water to a rapid boil. To add flavor and reduce stickiness, add salt (optional). 2. Add pasta and stir: return to rapid boil. 3. Cook uncovered, stirring occasionally. 4. Drain well. Serve as desired.


• Technical Memo: Construct a Tech Memo (2 pages minimum) describing observations you made

while conducting your experiment. Submit your Tech Memo as a PDF file on designated date to your instructor through iLearn. Hardcopy is NOT required. Please note that each student is required to submit their own Tech Memo (group discussion is allowed; however, you should write your own Tech Memo). For your Tech Memo, please use the following guidelines:

• 1” margin on all sides, 11 or 12 point font, Times or Arial fonts only, single – spaced. • Use Figures and Tables where necessary to illustrate your points, and provide Figure Captions

and Table Captions.

Please use this guide to describe your observations in the Discussion section of your Tech Memo:

i) To understand the way all the individual molecules pack together, place uncooked pasta on the plate. Can you pack them close together? Yes, uncooked pasta (each separate strand) are all lined up and can be put close together. What are the materials in which the atoms are situated in a repeating or periodic array over large atomic distances? Consult Chapter 3: The Structure of Crystalline Solids.

ii) To understand the way all the individual molecules pack together, place cooked pasta inside

the bowl(s). Insert the fork deep inside the pasta, wind a certain amount of pasta on the fork and lift up the fork, allowing the pasta to do what it wants. Make observations on the manner in which the pasta behaves. What are the materials in which long-range atomic order is absent? Consult Chapter 3: The Structure of Crystalline Solids.

iii) Is the shape of cooked pasta analogous to the shape of the single polymer chain molecule with numerous random kinks and coils produced by chain bond rotations?

iv) Some of the mechanical characteristics of polymers are a function of the ability of chain

segments to experience rotation in response to applied stresses or thermal vibrations. During Tensile testing of polymers in the region of upper yield point a small neck is formed. Upon further application of the load chains become oriented (i.e., chain axes become aligned parallel to the elongation direction. Chain molecules in amorphous region elongate in the direction of applied load. Did you find similarity of behavior in the pasta when it was raised with a fork above the bowl?

v) Construct Table 1 in your memo showing the results of your observations. Images of

uncooked, cooked and drawn pasta should be included in your report in Table 2.

ENGR 200: Materials of Engineering

Laboratory 4

Data Collection Sheet for Cooking of Pasta Experiment

Name: Date: Table 1: Cooking of Pasta Data

Material Amount of

spaghetti (g) Time of cooking

(minutes) Firmness Comments

Type of Pasta 450 4 Al dente

5 Firm

6 Tender

Note: In this Table the amount of pasta, time of cooking, and firmness are indicated are approximate. For each specific brand and type of pasta these values will be different.

In your Comments section you will describe the behavior of the pasta when it is drawn.

Technical Memo

To: (Instructor…) Date: (Date Submitted)

From: (Student…..)

Subject: (Experiment Performed)

Group Members: (Lab Partners)

Date Performed:

The write-up should include the following: Objectives, Procedures, Results, Conclusions, Tables,

Graphs, Sample Calculations, and Data Sheet(s).

References: (Including the lab manual and any text/publication referenced during write-up).

The objectives of each experiment are described in the lab manual. Clear experimental objectives

must be stated. If quoted or paraphrased from the lab manual, be sure to properly reference the


The procedure describes the conduct or “procedure” of the experiment indicating materials and the

significant equipment and/or instruments used.

Results and Conclusions of the experiment should be discussed. Important results should be

summarized and compared to published values (numerical values may be cited here). Known or

likely reasons should be stated to explain significant discrepancies and conclusions drawn from these

results. The conclusions should also reflect back to the stated objectives. Discuss what was learned

and whether or not the objectives were met.

Tables should include experimental values, published values (or theoretical), and their respective

percent differences.

Graph(s) must be prepared using a computer program.

Sample calculations: Please include a sample calculation for each significant calculation made. A

sample calculation should state the formula in general terms first.

The original data sheet(s) is the official and legal record of an engineering test. It is an important

document and must be well planned and executed. Data sheets must include the following: Test

Name (title), Test Personnel (group members), Date, and Location of Test. The equipment and

instruments used in the test should be identified (along with serial numbers and/or calibration dates if

available). All data columns must be identified with the variable name, symbol, and units.

NEVER erase a data entry, simply strike a line through or cross out any erroneous entry or mistake

so that this information is not lost.

There will be only ONE data sheet generated during experimentation per group.

File Names: Technical Memos shall be submitted as PDF files via iLearn. Name your file with your last name first, followed by your first initial, then 200, then your lab code, then the name of the lab. For example, if I would submit a memo named this way: MarsD_200_08_Tensile_Metals.

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