CHE 122 Finals

• What does the conservation of energy principle state?

  Energy can change form but cannot be created or destroyed. The total amount of energy remains constant during any interaction.
• What is Thermodynamics?


  The science of energy transfer. It originates from Greek words "therme" (heat) and "dynamis" (power), describing efforts to convert heat into power.
• What significant invention did Denis Papin create in 1679, and why is it important?

  Papin built a bone digester, a closed vessel confining steam to generate high pressure, introducing the concept of a piston and cylinder engine.
• What did Thomas Savery achieve in 1697 using Papin’s designs?

  He built the world’s first engine, leading to further developments like the Newcomen and Watt engines.
• Why is Nicolas Léonard Sadi Carnot called the "Father of Thermodynamics"?

  He published a mathematical discourse on heat, power, and engine efficiency, introducing concepts like reversibility and the Carnot cycle.
• When and how were the SI units established?

  Established in 1960 by the CGPM based on six fundamental quantities. A seventh unit, mole (mol), was added in 1971.
• What is the difference between primary and secondary dimensions?

  Primary dimensions (e.g., mass, length, time) are fundamental. Secondary dimensions (e.g., velocity, energy) are derived from primary dimensions
• Why were early engines inefficient?

  They converted less than 2% of input energy into useful work output.
• What does dimensional homogeneity mean in engineering?

  All terms in an equation must have the same unit, ensuring that only quantities with the same dimensions are added or equated.
• What are unity conversion ratios?

  Ratios equal to 1 and unitless, used to convert between units without altering the physical meaning of the quantity.
• What are specific properties?

  Extensive properties expressed per unit mass, such as specific volume or specific energy.
• What is the concept of continuum in thermodynamics?

  The assumption that matter is continuously distributed throughout the region it occupies, allowing properties like temperature and pressure to be defined at every point.
• Define density, specific volume, specific gravity, and specific weight.

  • Density (ρ): Mass per unit volume.
  • Specific Volume (v): Volume per unit mass, reciprocal of density.
  • Specific Gravity: Ratio of a substance's density to a standard substance (usually water).
  • Specific Weight: Weight per unit volume of a substance.
• What are the types of pressure in thermodynamics?

  • Absolute Pressure: Referenced to absolute vacuum.
  • Gauge Pressure: Pressure above atmospheric pressure.
  • Vacuum Pressure: Pressure below atmospheric pressure.
• What is hydrostatic pressure and its formula?

  Pressure due to a fluid's weight.Formula: P_hydrostatic=ρgh, where:

  • ρ: Density of the fluid.
  • g: Gravitational acceleration.
  • h: Depth below the surface.
• What factors does hydrostatic pressure depend on?

  It depends on fluid density, depth, and gravitational acceleration, but not on the amount of fluid, container shape, or cross-sectional area.
• What is a manometer, and how does it work?

  A device that measures small to moderate pressure differences using fluids in a U-tube. It balances pressures at different points.Key Equation: P_1=ρgh+P_atm​
• Why are inclined manometers used?

  To increase the resolution when reading the height of the fluid column, allowing more precise measurements.
• Why is the dimensional constant (g_c​) used in English units?

  It is needed to ensure consistency in equations involving force, as force is treated as a primary dimension in the English system.
• How does weight (W) differ in SI and English units?

  gc​ is constant and location-independent.
• What are the key components of a thermodynamic system?

  1. System: The matter or region under study.
  2. Surroundings: Everything outside the system.
  3. Boundary: Surface separating the system and surroundings (real or imaginary).

  Types of Systems:

  • Open System: Mass and energy can cross boundaries.
  • Closed System: Only energy can cross boundaries.
  • Isolated System: Neither mass nor energy crosses boundaries.
• What is a control volume in thermodynamics?

  A region in space selected for analysis, often enclosing devices like turbines or compressors.Key Feature: Boundaries, or control surfaces, may be real or imaginary, fixed, or moving.
• What is a thermodynamic state?

  A condition where all thermodynamic properties of a system are defined.
• What is a thermodynamic process?

  A change that takes a system from one state to another.
• What defines a thermodynamic cycle?

  A series of processes where the system's initial and final states are identical.
• What does equilibrium mean in thermodynamics?

  A state of balance with no unbalanced potentials or driving forces.
• What are the types of equilibrium in thermodynamics?

  • Thermal Equilibrium: Uniform temperature throughout the system.
  • Mechanical Equilibrium: Constant pressure throughout the system over time.
  • Chemical Equilibrium: No chemical reactions or changes in composition over time.
  • Phase Equilibrium: Mass of each phase remains constant over time.
• How does atmospheric pressure vary with altitude?

  Atmospheric pressure decreases with increasing altitude because there is less air above exerting force.
• Why does the acceleration due to gravity decrease with altitude?

  It decreases because the gravitational force is inversely proportional to the square of the distance from the Earth's center.
• What happens to temperature in an isothermal process?

  The temperature remains constant even if the volume or pressure changes.
• What is the work done in irreversible expansion with zero external force?

  The work is zero because no external pressure opposes the expansion.
• Why can enthalpy change (ΔH) be greater than internal energy change (ΔU)?

  Because enthalpy includes pressure-volume work (PΔV) in addition to internal energy changes.
• Kinetic Energy (KE)


  Energy due to motion.
• Potential Energy (PE)


  • Energy due to position in a gravitational field.
• Internal Energy (U)


  Microscopic energy from molecular interactions.
• What are the components of total energy?

  Total energy = Kinetic energy (KE) + Potential energy (PE) + Internal energy (U)
• What are the components of internal energy?

  Sensible energy, latent energy, chemical energy, and nuclear energy
• Sensible Energy


  Related to molecular kinetic energy.
• Latent Energy


  From intermolecular forces
• Chemical Energy


  • From atomic bonds in molecules.