Materials Science

Exam Booklet

Science Olympiad at the University of Pennsylvania

February 18 th , 2017

Instructions : Do not open the booklet until you are told to do so. Do not write on the test . You may take apart the test, but please return it in its correct order when finished. This test is split into three sections: multiple choice, short answers (begins on pg. 12), and the model station.

Teams will be called up to the model station by the event supervisor. The total amount of time for this test is 50 minutes. Good luck!

Multiple Choice: _____/134 Short Answer: ____/62 Model Station:____/32

Total:_____/228

Rank: ___

Multiple Choice

1) Order the following compounds/elements in terms of melting point from least to greatest: Fe, Cl 2 , NH 3 , C (diamond), MgO. [4 points] A) Cl 2 < NH 3 < Fe < MgO < C (diamond) B) NH 3 < Cl 2 < MgO < Fe < C (diamond) C) NH 3 < Cl 2 < C (diamond) < Fe < MgO D) Fe < Cl 2 < NH 3 < C (diamond) < MgO

2) Given the Figure below depicting interatomic separation (r) vs. potential energy, rank the magnitude of forces A, B, and C from weakest to strongest. [4 points] A) F A < F C < F B B) F B < F C < F A C) F A < F B < F C D) F C < F A < F B

3) The stress­strain curve below most likely corresponds to which material? [4 points] A) Brittle rubber B) Ductile steel C) Brittle aluminum D) Solid tungsten

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4) The contact angle between magnesium stearate and water is larger than that between lactose and water because: [3 points] A) Magnesium stearate is more hydrophilic than lactose B) Magnesium stearate contains more dissolved oxygen than water C) Magnesium stearate is more hydrophobic than water D) Magnesium stearate contains stearic acid 5) Which of the following contact angles corresponds to a hydrophobic drug particle? [3 points] A) 45° B) 30° C) 120° D) 90°

6) Out of the following choices, which is the strongest (ultimate tensile strength) material? [4 points] A) Wurtzite boron nitride B) Diamond C) Steel D) Graphene 7) Based on their fractures, order the materials from most ductile to least ductile. [4 points]

A) B, C, A B) A, B, C C) C, A, B D) All materials are equally ductile

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8) Given the table of electronegativities, which elements are most likely to form an intermetallic compound instead of a substitutional solid solution? [5 points]

A) Francium and tungsten B) Gold and aluminum C) Silicon and copper D) Fluorine and potassium E) Lithium and polonium

For questions 9­13, match each material with its structure at standard temperature and

pressure [1 point each] (FCC=face­centered cubic; HCP=hexagonal close­packed; BCC=body­centered cubic):

9) Aluminum A) FCC B) HCP C) BCC D) None of the above

10) Iron A) FCC B) HCP C) BCC D) None of the above

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11) Titanium A) FCC B) HCP C) BCC D) None of the above

12) Lead A) FCC B) HCP C) BCC D) None of the above

13) Magnesium A) FCC B) HCP C) BCC D) None of the above

14) In the electrochemical reaction of zinc and iron shown below, which element is being oxidized,and which is reduced? Which element is the oxidizing agent and which is the reducing agent? [3 points]

A) Fe is oxidized and Zn is reduced. Fe is the oxidizing agent and Zn is the reducing agent. B) Fe is reduced and Zn is oxidized. Fe is the reducing agent and Zn is the oxidizing agent. C) Fe is oxidized and Zn is reduced. Fe is the reducing agent and Zn is the oxidizing agent. D) Fe is reduced and Zn is oxidized. Fe is the oxidizing agent and Zn is the reducing agent.

15) Which modern method of materials production is not renewable? [3 points] A)Wind power B) Photovoltaic cells C) Nuclear energy D) Hydroelectricity

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Questions 16­23 deal with material selection: 16) Kobe Bryant is trying to build a new basketball court for his former high school. For the rims of the hoops, Kobe needs a material that has a high Young’s Modulus and an ultimate tensile strength of ~500 MPa. Out of the following choices, which material should he choose? [4 points] A) Platinum B) Copper alloys C) Low carbon steel D) Wrought iron

Use the plot below to answer questions 17­19

17) Which material class possesses intermediate weight and low stiffness? [4 points] A) Foams B) Natural materials C) Technical ceramics D) Elastomers

18) Based on the guide lines for minimum mass design, which material exhibits minimum deflection in centrifugal loading? [4 points] A) Steels B) Cork C) Neoprene D) Aluminum

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19) Which material can float on water? [3 points] A) PTFE B) PP C) Silicon elastomers D) Polyurethane

Use the plot of Strength vs. Density to answer questions 20 and 21 20) Where would materials that possess the highest strength­to­weight ratio lie on this plot? [4 points]

A) Upper right corner B) Bottom right corner C) Upper left corner D) Bottom left corner

21) The bubbles grouping each class are elongated along the strength axis, but not along the density axis. Why? [4 points]

A) Alloying and heat treatments have a strong effect on strength but little on density B) Most materials, with the exception of foams, naturally increase strength within small density

ranges C) Impurities in materials result in a wide range of strength values D) The more metallic a material is, the greater its range of strength

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Use the plot below to answer questions 22 and 23 22) Which material possesses the highest strength at the lowest weight? [4 points] A) Concrete B) Stone C) CFRP D) Cast irons

23) Which material is the stiffest at the lowest weight? [4 points] A) Ionomers B) Rigid polymer foams C) Cork D) Silicon

24) Based on the Mohs Hardness Scale (not given), what material should you choose if you need a material that can scratch corundum? [4 points] A) Diamond B) Topaz C) Steel D) Quartz

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25) Stephen Curry and the Golden State Warriors are reconstructing the Oakland Bay Bridge. For the foundation of the bridge, they need a corrosion­resistant material that has an ultimate tensile strength of ~440 MPa. Which material should they choose? [4 points] A) Nickel­copper B) Titanium C) Aluminum D) Synthetic gold alloys 26) A copper alloy is dropped into a pressurized liquid chamber. If you want to quantify the volume change of the copper alloy, what quantity should you measure? [4 points] A) Young’s modulus B) Shear modulus C) Bulk modulus D) Fatigue limit

27) Which of the following cations when added to fused titanium dioxide (TiO 2 ) will not increase its index of refraction? Use the table below. [4 points] A) Ni 2+

B) Cs +

C) Si 4+

D) Ba 2+

E) K +

28) You are designing a power grid that will supply electricity to the entire greater Philadelphia area. For this application, you will need the most electrically conductive material. Out of the following options, which should you choose? [4 points] A) Copper B) Silver C) Gold D) Zinc/brass

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29) You are working in a top­secret lab in Geneva in which absolute zero temperatures can be simulated for conductors. For such an experiment, you will need a superconductor. Given the plot of temperature vs. electrical resistivity below, which curve corresponds to a superconductor? [4 points]

A) A B) B C) Neither

Refer to the table below for questions 30­33.

30)Which material will experience the greatest reduction in area upon fracture? [4 points] A) A B) B C) C D) D E) E

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31) Which material is strongest? [3 points] A) A B) B C) C D) D E) E

32) Which material is stiffest? [3 points]

A) A B) B C) C D) D E) E

33) Which material is a ceramic? [3 points] A) A B) B C) C D) D E) E

Refer to the phase diagram below for questions 34­36.

34) Which point corresponds to the boiling point of the material at 1atm? [2 points] A) A B) B C) C D) D

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35) Which point corresponds to the melting point of the material at 1atm? [2 points] A) A B) B C) C D) D

36) Which point corresponds to the triple point of the material? [3 points]

A) A B) B C) C D) D

37) A cruise ship made of copper is resting at the pier. Copper corrodes naturally when in contact with water. Given the Galvanic Series below, which material will decrease the rate of corrosion when connected to the copper? [5 points]

A) Titanium B) Graphite C) Platinum D) Cast iron E) Bronzes (Cu­Sn alloys)

38) The minimum yield and tensile strengths of an alloy is 310MPa and its factor of safety is 5. Given this information, what is the working stress of the alloy? [4 points] A) 105 MPa B) 62 MPa C) 1550 MPa D) 265 MPa E) None of the above

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39) Which value of Poisson’s Ratio is volume­conserving? [4 points] A) 0.1 B) 1.0 C) 0.0 D) 0.5 40) What kind of defect boundary is shown in the following image (labeled A)? [4 points]

A) Grain boundary B) Screw dislocation C) Twin boundary D) Edge dislocation

Short Answers

1) Given the Figure below depicting the boiling points of different compounds, explain why H 2 O, HF, and NH 3 experience spikes in boiling points while the other compounds show a linear progression of boiling points. [10 points] (*the x­axis refers to ‘periods’ on the periodic table*)

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2) Copper has an atomic radius of 0.128nm, a face­centered cubic (FCC) structure, and an atomic weight of 63.5 g/mol. Compute its theoretical density () given the formula below. [16 points]

3) Use the data table below to plot the data and find the steady­state creep rate (min ­1 ): [20 points]

Time (min) Strain Time (min) Strain

0 0.000 16 0.135

2 0.025 18 0.153

4 0.043 20 0.172

6 0.065 22 0.193

8 0.078 24 0.218

10 0.092 26 0.255

12 0.109 28 0.307

14 0.120 30 0.368

Assumptions: (i) Given data is accurate (ii) Constant temperature (iii) Constant stress

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4) Use the phase diagram of H 2 O­NaCl to answer parts (a) and (b). [16 points]

(a) Using the phase diagram above, briefly explain how spreading salt on ice that is at a temperature below 0冽 can cause ice to melt.

(b) At what temperature is salt no longer useful in causing ice to melt?

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Corresponds to Final version of Materials Science Test 1.) A 2.) B 3.) B 4.) C 5.) C 6.) D 7.) B 8.) B 9.) A 10.)C 11.)B 12.)A 13.)B 14.) D 15.) C 16.) C 17.) D 18.) C 19.) B 20.) C 21.) A 22.) C 23.) D 24.) A 25.) B 26.) C 27.) C 28.) B 29.) A 30.) B 31.) D 32.) E 33.) E 34.) C 35.) B 36.) A 37.) D 38.) B 39.) D 40.) C

Short Answers 1) Concept: Hydrogen bonding vs. london dispersion and weaker intermolecular forces. An example of a good response would be: “Boiling point is a function of intermolecular forces of attraction within molecules. Among the given molecules, H2O and HF can form reasonably strong intermolecular hydrogen bonds. These two molecules are expected to have higher boiling points. In NH3, hydrogen bonds can also form, so NH3 would follow HF in that sequence. In the molecules of methane and neon, however, london dispersion forces are the only possible intermolecular forces.” 2.) 8.89 g/cm 3

3.) 9.667 x 10 ­3 min ­1 ; complete answer shown on MatSci Graph Questions document

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Model Questions

1.) Model 1 HCP ­The one that’s stacked ABAB 2.) BCC model 2­ Yellow structure is BCC 3.) BCC model 2 4.) FCC model 3­ Black structure is FCC 5.) FCC