Heat and Thermal Energy

Heat is a form of energy transferred due to a temperature difference. Temperature measures the average kinetic energy of particles in a substance — higher temperature means faster-moving particles. The SI unit of heat energy is the Joule (J); temperature is measured in Celsius (°C) or Kelvin (K), where K = °C + 273. Heat transfer occurs by three mechanisms: conduction (particle-to-particle vibration, mainly in solids — metals conduct well), convection (bulk movement of a fluid — hot fluid rises, cool fluid sinks, forming convection currents), and radiation (electromagnetic waves — infrared — no medium needed; dark matt surfaces emit and absorb best; shiny surfaces reflect). Specific heat capacity (c) is the energy needed to raise 1 kg of a substance by 1°C: Q = mcΔT. Water's high specific heat capacity (4200 J/kg°C) makes it ideal for cooling systems and explains coastal climates. Latent heat is the energy absorbed or released during a change of state with no temperature change.