SCIENCE SAC 2013 GENERAL DIRECTIONS: DO NOT OPEN EXAM UNTIL TOLD TO DO SO. Ninety minutes should be ample time to complete this contest, but since it is not a race, contestants may take up to two hours. If you are in the process of actually writing an answer when the signal to stop is given, you may finish writing that answer. Papers may not be turned in until 30 minutes have elapsed. If you finish the test in less than 30 minutes, remain at your seat and retain your paper until told to do otherwise. You may use this time to check your answers. All answers must be written on the answer sheet provided. Indicate your answers in the appropriate blanks provided on the answer sheet. You may place as many notations as you desire anywhere on the test paper except on the answer sheet, which is reserved for answers only. You may use additional scratch paper provided by the contest director. All questions have ONE and only ONE correct (BEST) answer. There is a penalty for all incorrect answers. If a question is omitted, no points are given or subtracted. On the back of this page is printed a copy of the periodic table of the elements. You may wish to refer to this table in answering the questions, and if needed, you may use the atomic weights and atomic numbers from the table. Other scientific relationships are listed also. Silent hand-held calculators that do not need external wall plugs may be used. Graphing calculators that do not have built-in or stored functionality that provides additional scientific information are allowed. Small hand-held computers are not permitted. Calculators that accept memory cards or memory sticks are not permitted. Each contestant may bring one spare calculator. All memory must be cleared. SCORING: All questions will receive 6 points if answered correctly; no points will be given or subtracted if unanswered; 2 points will be deducted for an incorrect answer. University Interscholastic League Making a World of Difference
1 1A 1 H 1.01 2A 2 Periodic Table of the Elements 3A 13 4A 14 5A 15 6A 16 7A 17 8A 18 2 He 4.00 3 Li 6.94 4 Be 9.01 5 B 10.81 6 C 12.01 7 N 14.01 8 O 16.00 9 F 19.00 10 Ne 20.18 11 Na 22.99 12 Mg 24.31 3B 3 4B 4 5B 5 6B 6 7B 7 8B 8 8B 9 8B 10 1B 11 2B 12 13 Al 26.98 14 Si 28.09 15 P 30.97 16 S 32.07 17 Cl 35.45 18 Ar 39.95 19 K 39.10 20 Ca 40.08 21 Sc 44.96 22 Ti 47.87 23 V 50.94 24 Cr 52.00 25 Mn 54.94 26 Fe 55.85 27 Co 58.93 28 Ni 58.69 29 Cu 63.55 30 Zn 65.41 31 Ga 69.72 32 Ge 72.64 33 As 74.92 34 Se 78.96 35 Br 79.90 36 Kr 83.80 37 Rb 85.47 38 Sr 87.62 39 Y 88.91 40 Zr 91.22 41 Nb 92.91 42 Mo 95.94 43 Tc (98) 44 Ru 101.07 45 Rh 102.91 46 Pd 106.42 47 Ag 107.87 48 Cd 112.41 49 In 114.82 50 Sn 118.71 51 Sb 121.76 52 Te 127.60 53 I 126.90 54 Xe 131.29 55 Cs 132.91 56 Ba 137.33 57 La 138.91 72 Hf 178.49 73 Ta 180.95 74 W 183.84 75 Re 186.21 76 Os 190.23 77 Ir 192.22 78 Pt 195.08 79 Au 196.97 80 Hg 200.59 81 Tl 204.38 82 Pb 207.20 83 Bi 208.98 84 Po (209) 85 At (210) 86 Rn (222) 87 Fr (223) 88 Ra (226) 89 Ac (227) 104 Rf (261) 105 Db (262) 106 Sg (266) 107 Bh (264) 108 Hs (277) 109 Mt (268) 110 Ds (281) 111 Rg (272) 112 Cn (285) 58 Ce 140.12 90 Th 232.04 59 Pr 140.91 91 Pa 231.04 60 Nd 144.24 92 U 238.03 61 Pm (145) 93 Np (237) 62 Sm 150.36 94 Pu (244) 63 Eu 151.96 95 Am (243) 64 Gd 157.25 96 Cm (247) 65 Tb 158.93 97 Bk (247) 66 Dy 162.50 98 Cf (251) 67 Ho 164.93 99 Es (252) 68 Er 167.26 100 Fm (257) 69 Tm 168.93 101 Md (258) 70 Yb 173.04 102 No (259) 71 Lu 174.97 103 Lr (262) Some Standard Properties of Water density property symbol value specific heats ice water steam ρ cice cwater csteam 1.00 g cm -3 1000 kg m -3 2.09 J g -1 K -1 4.184 J g -1 K -1 2.03 J g -1 K -1 Pressure 1 atm = 760 torr = 101325 Pa = 14.7 psi 1 bar = 10 5 Pa = 100 kpa heat of fusion Hfus or Lf 334 J g -1 heat of vaporization Hvap or Lv 2260 J g -1 index of refraction n 1.33 autoionization Kw 1.0 10-14 Energy 1 cal = 4.184 J 1 L atm = 101.325 J 1 Cal = 1 kcal 1 hp = 746 W
Various Physical Constants property symbol value Various Physical Constants property symbol value universal gas R 8.314 J mol -1 K -1 62.36 L torr mol -1 K -1 electron rest mass me 9.11 10-31 kg 0.000549 u Planck s Planck s reduced Boltzmann Stefan- Boltzmann h h/2π 0.08206 L atm mol -1 K -1 1.987 cal mol -1 K -1 6.626 10-34 J s 4.136 10-15 ev s 1.054 10-34 J s 6.582 10-16 ev s kb 1.38 10-23 J K -1 σ 5.67 10-8 W m -2 K -4 speed of light c 3.00 10 8 m s -1 0.511 MeV c -2 proton mass mp 1.6726 10-27 kg 1.00728 u 938.3 MeV c -2 neutron mass mn 1.6749 10-27 kg atomic mass unit earth mass u 1.008665 u 939.6 MeV c -2 1.6605 10-27 kg 931.5 MeV c -2 5.972 10 24 kg speed of sound (at 20 C) vair 343 m s -1 earth radius 6.371 10 6 m acceleration of gravity g 9.80 m s -2 moon mass 7.348 10 22 kg gravitational G 6.67 10-11 N m 2 kg -2 sun mass 1.989 10 30 kg Avogadro s number elementary charge NA 6.022 10 23 mol -1 e 1.602 10-19 C Faraday F 96485 C mol -1 Coulomb s law k 8.988 10 9 N m 2 C -2 distance earth- moon distance earth- sun permittivity of free space permeability of free space 3.844 10 9 m 1.496 10 11 m ε0 8.85 10-12 F m -1 µ0 4π 10-7 T m A -1
Sample Science Questions SAC 2013 Biology Questions (1 3) 1. How many neutrons are found in the isotope C 14? A) 12 B) 6 C) 7 D) 8 E) 18 2. How many hydrogen bonds are in a single molecule of water? A) 0 B) 2 C) 6 D) 8 E) 10 3. The graph below shows the results of an analysis of stained, dividing cells from two different tissues. The results from Tissue 1 are indicated by the solid line, and the results from Tissue 2 are indicated by the dotted line. Which peaks correspond to cells that are in G1 in both tissues? A) Peaks A and B B) Peaks A and D C) Peaks B and C D) Peaks A and C E) Peaks C and D Chemistry Questions (4 6) 4. Consider the following gas phase reaction: 2 A (g) + 3 B (g) 2 C (g) 10 moles of A and 12 moles of B are put into a large container and allowed to react completely. What is the mole fraction of C after the reaction? A) 0.20 B) 0.40 C) 0.60 D) 0.80 E) 1.00 5. 21.4 g of NH 4 Cl (53.5 g/mol) is dissolved into 1600 ml of water. What is the ph of this solution? ( K b of ammonia is 1.8 10 5 ) A) 2.67 B) 4.74 C) 4.93 D) 5.75 E) 7.00 F) 6.25 G) 9.07 H) 9.26 I) 9.86 6. The heat of combustion ( H comb ) for propane is about 2200 kj/mol. What is the approximate amount of heat released when 100 grams of propane undergoes combustion? A) 1000 kj B) 2000 kj C) 3000 kj D) 4000 kj E) 5000 kj F) 6000 kj G) 7000 kj H) 8000 kj I) 9000 kj
Physics Questions (7 9) 7. You and your friend throw rocks off of a rooftop. One rock is thrown at an angle of 25 above the horizontal and the other rock is thrown horizontally. If both rocks are thrown at the same time with the same initial speed, then which of the following is true? You may neglect air resistance for this problem. A) The rocks hit the ground at the same time with the same speed. B) The rocks hit the ground at the same time with different speeds. C) The rocks hit the ground at different times with the same speed. D) The rocks hit the ground at different times with different speeds. E) Cannot be determined from the information given. Sample Science Questions SAC 2013 8. A small child throws a bouncy ball. The position vector of the bouncy ball is given by r(t) = [1.7 m + (15 m/s)t]i + [(16 m/s)t (4.9 m/s 2 )t 2 ]j, where i and j are unit vectors in the horizontal and vertical directions respectively. What is the velocity vector, v(t), of the bouncy ball? A) (15 m/s)i B) (16 m/s)j C) [16 m/s (9.8 m/s 2 )t]j D) (15 m/s)i + [16 m/s (9.8 m/s 2 )t]j E) (31 m/s)i [(9.8 m/s 2 )t]j 9. An LC circuit (without a generator) is constructed by attaching a 5.0 µf capacitor that is charged to 30 V to a 6.0 µh inductor. What is the frequency of oscillation? A) 2.9 10 4 Hz B) 1.8 10 5 Hz C) 1.1 10 6 Hz D) 5.3 10 9 Hz E) 1.9 10 14 Hz University Interscholastic League page 2
Sample Science Questions SAC 2013 Biology Answers 1. Answer: D. The isotope number is the sum of the protons and neutron. Carbon has an atomic number of 6 (6 protons) so the C 14 isotope has 14-6 protons=8 neutrons. 2. Answer: A. There are only polar covalent bonds in a single molecule of water. Hydrogen bonds form between water molecules as a result of the attraction between the partial negative charge of the oxygen of one water molecule to the partial positive charge of the hydrogen in a different water molecule. 3. Answer: A. Cells in G 1 of the cell cycle have half the quantity of DNA as do cells in the S or G 2 phase of the cell cycle. Therefore, the peaks A and B are cells that have not yet undergone DNA replication. After the S phase, the quantity of DNA is doubled in the cell until after the end of mitosis. Chemistry Answers 4. Answer: D. 10 moles of A (3/2) = 15 moles B needed, therefore the 12 moles of B makes it the limiting reactant. 12 mol B reacts completely with 12(2/3) = 8 mol A to give 8 mol of C. So AFTER the reaction there are zero mol B, 2 mol A, and 8 mol C. The mole fraction of C = 8/(8+2) = 8/10 = 0.80 5. Answer: C. 21.4/53.5 = 0.40 mol 1.6 L = 0.25 M NH 4 +. NH 4 is a weak acid with a K a = K w /K b = 1e-14/1.8e-5 = 5.56e-10. [H + ] (.25 5.56e-10) 0.5 = 1.18e-05 -log ph = 4.93. 6. Answer: E. Propane = C 3 H 8 = 44 g/mol. 100/44 = 2.27 mol. 2.27(2200) = 5000 kj Physics Answers 7. Answer: C. As the rocks move from the rooftop to the ground the only force acting on them is the force of gravity (since we will neglect air resistance), thus the mechanical energy will be conserved during this motion. Since they start with the same speed at the same location then they will have the same initial mechanical energy, and because they end at the same location then they will have the same kinetic energy and therefore the same speed. However since the y-components of their initial velocity vectors are different, they will take different amounts of time to reach the ground. This question is representative of the conceptual questions that will be found on the contests. 8. Answer: D. Since v(t) = (d/dt) {r(t)} = (d/dt) { [1.7 m + (15 m/s)t]i + [(16 m/s)t (4.9 m/s 2 )t 2 ]j } = (15 m/s)i + [16 m/s (9.8 m/s 2 )t]j. This question is representative of the calculus problems that may be found on the contests beginning this season. 9. Answer: A. The frequency of oscillation for an LC circuit is f = 1/[LC] ½ = 1/[(5.0 E-6)(6.0 E-6)] ½ = 2.9 E+4 Hz. This question is representative of the ac circuit problems that may be found on the contests beginning this season.