Thermal Energy

Transfer of Thermal Energy

• Thermal Energy vs. Temperature
    - Thermal energy: movement of particles (atoms, molecules, ions).
    - Temperature: measure of how hot or cold an object is.
    - SI unit of temperature: Kelvin (K).

• Heat Transfer
    - Thermal energy transfers from hot to cold objects.
    - Heat: flow of thermal energy due to temperature difference.

• Expansion and Contraction
    - Matter generally expands when heated and contracts when cooled.
    - Expansion: increase in volume; Contraction: decrease in volume.
    - Affects solids, liquids, and gases.

• Thermal Conductivity
    - Different materials have different rates of thermal energy transfer.
    - Good conductors (e.g., metals) transfer thermal energy better than poor conductors (e.g., wool).

• Processes of Thermal Energy Transfer
    - Conduction: transfer of thermal energy through a medium without flow (done via particle vibration and collisions).
    - Convection: mass movement of molecules in fluids due to density differences; occurs only in fluids.
    - Radiation: transfer of thermal energy through electromagnetic waves; does not require a medium.

• Applications
    - Conduction: cooking utensils, heating elements.
    - Convection: air conditioning systems, heating elements in kettles.
    - Radiation: solar panels, white houses for heat reflection.

• Factors Influencing Radiation
    - Emission/Absorption: influenced by color, texture, surface area, and surface temperature.

• Thermal Equilibrium
    - Achieved when two bodies reach the same temperature; no net thermal energy transfer occurs.

• Common Errors
    - Misunderstanding conduction as only applicable to solids.
    - Failing to differentiate between heat emission and absorption in thermal processes.