PROBLEM 2 (20 POINTS) A number of studies have been conducted on the diffusion of substances such as water and oxygen in plastics with particular relevance to the food packaging industry. It turns out that at 30°C, the diffusivity of water in polyvinylidene chloride (PVDC) (a.k.a. Saran™) is 9.1×108 cm²/s.1 Imagine you cover a glass with 100 mL (5.55 mol) of water with a 10 μm thick PVDC film as depicted to the right. Assuming that the water concentration on the lower surface (inside the glass) of the PVDC is 1.7 mol/m³ (based on the equilibrium vapor pressure of 4.25 kPa for water at 30°C) and "dry air" conditions (no water, a.k.a. 0% humidity) are maintained outside the glass, determine how long (in years!!!) it will take for the water to completely evaporate from the glass assuming it can only escape the glass by diffusion through the PVDC film and that the temperature is constant at 30°C. The diameter at the top of the glass is 10 cm.

A student working 3.0m away from you in a chemistry lab performs an experiment which creates a bad odor. It takes a while for the smell to get to you (air currents negligible). You are able to move 2.0m further away from the source but the smell catches up with you in another 60 seconds. What is the diffusion coefficient in the air for the molecules you smell?

10:52 AM 50 SALE Noll 2.0376 K/S Downloaded by Mothusi Mahlathini (mothusimothusi194@gmail.com) SECTION A Question 1 (a) (b) (i) List and briefly explain the four components of the discipline of materials science and engineering in a linear relationship. [4] (ii) Using a flowchart, classify engineering materials, indicating the types of polymers. [5] The ionic radii and coordination number of NaCl is 0.414 -0.732 and 6 respectively. Using the data below, show that FeO has the structure of NaCl. [8] (c) Ion Ionic radius (cation/anion) (nm) Al3+ 0.053 Fe3+ 0.069 02- 0.140 CI- 0.181 F- 0.133 Fe2+ 0.077 Determine the Miller indices for the directions in the cubic unit cell shown below (Fig. Q1): [8] Figure Q1 Downloaded by Mothusi Mahlathini (mothusimothusi194@gmail.com) Question 2 (a) (b) T (i) List and briefly explain the six properties of solid materials. [6] (ii) Using a flowchart, classify metals and alloys. [6] BCC lithium has a lattice parameter of 3.5089 x 10-10 m and contains 200…

In the following multiple-choice problems, circle the one answer which best completes the Sentence (i) (iii) (iv) (v) The glass transition temperature of polystyrene is about 110 °C. Relative to a sample at 120 °C, at room temperature polystyrene is: a. orders of magnitude more viscous b. slightly more viscous c. equally as viscous less viscous d. e. none of the above. The glass transition temperature of polystyrene is about 110 °C. Relative to a sample at 120 °C, a sample of polystyrene at 130 °C is: a orders of magnitude more viscous b. slightly more viscous c. equally as viscous d. less viscous e. none of the above. Suppose a tensile test is performed on two identical materials except that one has a deep scratch on its surface whereas the other is perfectly smooth. Relative to the smooth specimen, the test will find that the scratched specimen has a lower. a. elasticity b. yield stress c. tensile stress d. elongation to failure e. none of the above. Thermoplastic polymers such as…