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Unformatted text preview: Page 1 of 6 ChE 359 Homework #1 Solutions prepared by Yandi Hu & Chris Singer 1. (25 points) Define the thermodynamic system in the following scenarios and classify the system as open, closed, adiabatic, or isolated. Justify your classification by noting what properties, if any, are being exchanged with the surroundings. a. (5 points ) A fertilized chicken egg in a constant-temperature (isothermal) incubator. The system is the egg and the boundary is the shell. It is an open system because it exchanges heat and particles (e.g., air) with the surroundings. b. (5 points) A cell suspended in an isothermal culture medium. The system is the cell and the boundary is the cell membrane. It is an open system because it exchanges heat (e.g., exothermic reactions within the cell release heat into the large surrounding bath), volume (e.g., cell movement), and particles (e.g., water, nutrients, ions) with the surroundings. c. (5 points) A collection of cells suspended in a culture medium contained within a covered plastic Petri dish. The dish itself is sitting in an isothermal incubator, and carbon dioxide is being supplied to the incubator at a constant level. The system is the cells+culture medium and the boundary is the covered Petri dish+cover. It is a closed system because it exchanges heat but does not exchange particles with the surroundings. d. (5 points) An aqueous solution contained in a sealed, thermally insulated flask. The system is the aqueous solution and the boundary is the flask. It is an isolated system because it cannot exchange heat (i.e., thermally insulated or adiabatic), volume (i.e.., solid flask walls), or particles (i.e., sealed) with the surroundings. e. (5 points) A soap bubble being blown through a wand. The system is the soap bubble and the boundary is the soap film. It is an open system because it exchanges heat, volume, and particles with the surroundings (e.g., the person blowing the bubble). 2. (20 points) Consider the process of freezing an ice cube. The ambient temperature is 0 C and the ambient pressure is 1 atm. The volume of water to be frozen is 8 cm 3 . At 0 C, the density of liquid water is 1.000 g/cm 3 , and the density of solid ice is 0.915 g/cm 3 ....
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