Thermal physics - OneNote

Thermal Physics

Fixed States of Matter

  • Solids: Fixed shape and volume; particles vibrate in fixed positions; balanced intermolecular forces; incompressible.

  • Liquids: No fixed shape but fixed volume; particles move around each other with weaker bonds; balanced forces; incompressible.

  • Gases: No fixed shape or volume; independent particles with no attractive forces; compressible.

Kinetic Particle Model (Kinetic Theory)

  • Explains the behavior of solids, liquids, and gases based on particle motion and forces.

Historical Understanding of Heat

  • Caloric Theory: Heat was thought to be a fluid (caloric) that moved between substances; later disproven.

Internal Energy (U)

  • Total kinetic energy (KE) and potential energy (PE) of particles in a substance.

  • Internal energy in solids and liquids includes KE and PE; in gases, it consists of only KE due to broken bonds.

Temperature (T)

  • Measures how hot/cold a body is; related to the average kinetic energy of molecules.

  • Higher particle speed correlates with higher temperature.

Celsius Scale

  • Solids and liquids expand when heated; thermometers utilize liquid expansion for measurement.

Absolute Zero

  • Theoretical lowest temperature ( −273.15 °C or 0 K); where molecular motion ceases.

Heat Transfer

  • Heat moves from higher to lower temperature; measured in Joules (J).

  • Conduction, Convection, Radiation are the three modes of heat transfer.

Specific Heat Capacity (c)

  • Amount of heat required to raise the temperature of 1 kg of a substance by 1 °C or 1 K.

  • Water has a high specific heat capacity (4180 J/kg K).

Phase Changes

  • Temperature does not change during phase transitions; energy is used to change the state rather than increase temperature.

  • Specific latent heat is required for phase changes (fusion and vaporization).

Refrigeration

  • Uses evaporation to cool; modern refrigerators employ a closed-loop coolant system.

  • Evaporative coolers work by evaporating water to cool air; effective in dry climates.

Efficiency of Heat Transfer

  • Efficiency calculated as useful energy/total energy used, often presented as a percentage.

  • Sankey diagrams illustrate energy flow and efficiency visually.