Thermodynamics Lecture 2

Ground Rules

• Attend classes promptly and listen attentively
• Come to class with a pen and paper and solve related problems copiously
• Obtain and consult the recommended textbooks regularly
• Familiarize yourself with your student handbook and adhere to its provisions
• Avoid negative peer pressure
• Focus on reading, studying, and meditating on your books

Learning Objectives

• Understand the fundamental concept of a pure substance
• Discuss the physics of phase-change processes
• Demonstrate the use of property tables

Working Substance Quality

• A working fluid is the matter contained within a thermodynamic system's boundaries
• A working fluid can be in solid, liquid, or gaseous phase or a combination of phases
• Phase refers to a quantity of matter homogeneous in both chemical composition and physical structure
• Three common phases: solids, liquids, and gases
• Solids: closely packed molecules, high molecular forces, definite shape and volume
• Liquids: less closely packed molecules, weaker molecular forces, fluid shape, and definite volume
• Gases: freely moving molecules, weakest molecular forces, no shape, and container-defined volume

Phase Change Types

• Condensation: gas changes to liquid
• Vaporization: liquid changes to gas
• Freezing: liquid changes to solid
• Melting (fusion): solid changes to liquid
• Sublimation: solid changes to gas without becoming liquid
• Deposition: gas changes to solid without becoming liquid

Pure Substances

• A substance with a fixed chemical composition throughout is called a pure substance
• A mixture of two or more phases of a pure substance is still a pure substance if the chemical composition is the same
• Saturation temperature (Tsat): the temperature at which a pure substance changes phase at a given pressure
• Saturation pressure (Psat): the pressure at which a pure substance changes phase at a given temperature

Pure Substance Concepts

• Compressed liquid (subcooled liquid): liquid that is not about to vaporize
• Saturated liquid: liquid that is about to vaporize
• Saturated vapor: vapor that is about to condense
• Saturated liquid-vapor mixture: substance at a state between saturated liquid and saturated vapor
• Superheated vapor: vapor that is not about to condense
• Degree of superheat: the difference between the actual temperature of a superheated vapor and the saturation temperature

Properties of Wet Vapor and Steam Table

• Dryness fraction (x): the mass of dry vapor in 1 kg of the mixture of saturated liquid and saturated vapor
• Wetness fraction (1-x): the mass of saturated liquid in 1 kg of the mixture
• Properties of wet vapor and steam table: used to determine properties of wet vapor and steam

This quiz is based on the second lecture of thermodynamics, covering the fundamentals of the topic. It is designed to test students' understanding of the concepts and principles of thermodynamics. Students are expected to have a solid grasp of the subject matter and be able to apply it to solve problems.