ss_4 - Problem Set 4 13-344 Due: Tuesday, 28 September,...

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Unformatted text preview: Problem Set 4 13-344 Due: Tuesday, 28 September, 2004 Fall 2004 at beginning of lecture In the following two multiple-choice questions, indicate the single and best answer. 1. Cement a) is a semiconductor; b) is formed by a drying reaction; 0) is used primarily in biomedical applications; ©cures in stages over a period of several months or years; c) none of the above. 2. Polymers are poor electrical conductors, because: a) carbon atoms have only six electrons; @ the filled valence band and empty conduction band are separated by a large energy gap; c) different polymer molecules are bonded to each by weak secondary bonds; d) they exhibit thermoplastic behavior; e) none of the above. 3. Suppose you are trying to select a material for use as the hood of a car. List the important properties required by this application and briefly indicate why a polymeric material would or would not be good for it. 4. The average molecular weight of a solid 1 gram sample of poly(ethylene) is 400,000 g/mole. Calculate the average degree of polymerization. Estimate the length of the average molecule in this sample. In the solid, with (roughly) what probability do you expect that the ends of this molecule will be this distance apart? Briefly justify your answer. 5. The boiling temperatures of methane (CH4), carbon tetrachloride (CCl4), and water (H20) are l l 1 K, 350 K, and 373 K, respectively. For each of these three molecules: a) make a 2—d sketch the structure of the molecule; b) calculate the percent ionicity of the C—H; C-Cl, and 0-H bonds 0) develop a brief argument justifying the magnitudes and general order of boiling temperatures for these three molecules. 6. Is the glass transition temperature of an elastic band above or below room temperature? Briefly justify your answer. T @Wjfi {4% A Q M mtg; Afiwfiz I; if: {nigh/flak We“ t“ vi.,i:..:f-“rvl~*c; h E-tassw liberals \‘12. F renew . KSELOW T “(T mama‘s Vial-r 58. at . 6 1 ' ' $0.3 $\S\ vuva u: .. aux/L w. =. Wm M: was 17.. W; Eva/x mxcx .wwcp U§£k3 N WSWKPAMwM Whuzfir‘honca. \P at.- .-: ,: - L 0M0 Na? ' 'F-M-d‘s w :94 \LY Ms: W» Wop TWA k Cat M Vilma; Mots? Vow mgm- {3:33 W WNLS ‘1 ".3 AM NCOBW W‘i‘rk ‘1~%$%\L& {\bu‘m‘és Nd: Lithuch DD?— - 5 W‘: CDWMMS ask W24 . v' T 1) W " WM$M W§LCWMS Rfinvvlé; Wu: oo" mu ' womb BL To * NE? W m at: -- aw «Ma may» ‘N—Jw. FuALCI an“ M057 WWW TMST macaw: MINCE ' \- . msmcmxfi To * NW“ "w n \W bmqmz, mm mm Wfimuh t ~25 ’ En CLUT- 1.31.) {Tth “00 01:0 q' n '17-] ' 7 :— LLW 000 3/ z w. 300 .- cull- NY’; 'd" i: EMMY”: MS ii. MDme? we “£8 o. \‘R ow w‘wwz ow “‘8 . . Wm. mxS'“L\ wt, -.3' ‘r \g 'ZXOJSVXAM‘ 0.30%nh 1" Tad”) as- M Mawlmgw T‘D W2. 3-“. ‘W ’30 WT. We “0 WT W; WLHLUL “No A . n ni.’ . x I F‘“ 4— B 5% ~ka in.) * TD“ a I Q m 9 g c T: mu; '5va gnaw. (3 u‘ - *W ’r |w .“ \iv " .— ‘f — - - P‘ C\’ (gm «2.2:; ML — - =2k =75 ’IL :%0 1:33’ o/DWSJ 1 4 to a 6 [Q L \s .- $1552. \ ~ E QDWUSQ \‘r' \5 ms o. g» \MVDL , N43 _ ‘" mt 4' CU M" Ebbwhnhb \S MU" o»: mum we €59) L v: WW up mewum '~ .41”. T h)! Uzi h; ME . “WRLFTW ma: W3 . ‘ " \S ['3' . T \S \ m;- UK M (3:.th T " W» No mm - R9482 ' \‘\‘ 5 ".2; mi: HEM MD LENSES. {Tde ...
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ss_4 - Problem Set 4 13-344 Due: Tuesday, 28 September,...

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