ME 311 Chapter 3 lecture

ME 311 Chapter 3 lecture - Chapter 3 PROPERTIES OF PURE...

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Chapter 3 PROPERTIES OF PURE SUBSTANCES
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2 Objectives Introduce the concept of a pure substance. Phase-change processes. Illustrate the P - v , T - v , and P - T property diagrams and P - v - T surfaces of pure substances. Determine thermodynamic properties of pure substances from tables of property data. Ideal Gas More precise equations of state & methods to obtain properties
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PURE SUBSTANCE Pure substance : A substance that has a fixed chemical composition throughout. Air is a mixture of several gases, but it is considered to be a pure substance. 3 Nitrogen and gaseous air are pure substances. A mixture of liquid and gaseous water is a pure substance, but a mixture of liquid and gaseous air is not.
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PHASES OF A PURE SUBSTANCE 4 The molecules in a solid are kept at their positions by the large springlike inter-molecular forces. The arrangement of atoms in different phases: ( a ) molecules are at relatively fixed positions in a solid, ( b ) groups of molecules move about each other in the liquid phase, and ( c ) molecules move about at random in the gas phase.
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PHASE-CHANGE PROCESSES OF PURE SUBSTANCES Compressed liquid (subcooled liquid) : A substance that it is not about to vaporize. Saturated liquid : A liquid that is about to vaporize. 5 At 1 atm and 20°C, water exists in the liquid phase ( compressed liquid ). At 1 atm pressure and 100°C, water exists as a liquid that is ready to vaporize ( saturated liquid ).
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Saturated liquid vapor mixture : The state at which the liquid and vapor phases coexist in equilibrium. Saturated vapor : A vapor that is about to condense. Superheated vapor : A vapor that is not about to condense (i.e., not a saturated vapor). 6 ( saturated liquid–vapor mixture ). ( saturated vapor ). ( superheated vapor ).
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7 T - v diagram for the heating process of water at constant pressure.
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The temperature at which water starts boiling depends on the pressure; therefore, if the pressure is fixed, so is the boiling temperature. Saturation temperature T sat : The temperature at which a pure substance changes phase at a given pressure. Saturation pressure
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This note was uploaded on 09/21/2009 for the course ME 311 taught by Professor Ferrenberg during the Fall '09 term at Nevada.

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ME 311 Chapter 3 lecture - Chapter 3 PROPERTIES OF PURE...

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