Thermal Energy Notes

Temperature

Temperature measures how hot or cold a body is and reflects the average kinetic energy of its molecules. The SI unit for temperature is Kelvin (K).

Heat Transfer

Heat energy always flows from a warmer to a cooler place when there is a temperature difference.

Methods of Heat Transfer

  1. Conduction: Particle-to-particle contact, most effective in solids.
  2. Convection: Fluid movement in liquids and gases (e.g., air conditioners, boiling water).
  3. Radiation: Transfer via electromagnetic waves (e.g., the sun's energy reaching Earth).

Temperature Scales

There are three main temperature scales:

  1. Celsius: Widely used.
  2. Fahrenheit: Primarily used in the USA.
  3. Kelvin (Absolute Scale): Starts at absolute zero (0 K), the lowest possible temperature where molecular motion ceases.

Temperature Scale Comparison

  • Fahrenheit: 32 °F to 212 °F
  • Celsius: 0 °C to 100 °C
  • Kelvin: 273 K to 373 K

Fixed Points on the Celsius Scale

  • Lower Fixed Point: 0 °C (freezing point of pure water), corresponds to 32 °F and 273 K
  • Upper Fixed Point: 100 °C (boiling point of pure water), corresponds to 212 °F and 373 K

Temperature Conversion

  • 0 K = -273 °C
  • Celsius to Kelvin: Celsius + 273
  • Kelvin to Celsius: Kelvin - 273
  • Absolute Zero: -273 °C or 0 K (point of no particle energy)
  • °C to °F: (°C \times 1.8) + 32
  • °F to °C: (°F – 32) ÷ 1.8