Energy - Thermal Energy and Heat Transfer

Thermal energy is the total internal energy of an object due to the kinetic energy of its atoms and molecules, measured in Joules ($J$).

Temperature is a measure of the average kinetic energy of the particles in a substance, typically measured in degrees Celsius ($^\circ C$) or Kelvin ($K$).

Heat is the flow of thermal energy from a high-temperature object to a low-temperature object until thermal equilibrium is reached.

Conduction is the transfer of heat through direct contact in solids. Metals are excellent conductors because they contain 'free' electrons that transfer energy quickly.

Convection is the transfer of heat in fluids (liquids and gases). As a fluid is heated, it expands, becomes less dense, and rises, while cooler, denser fluid sinks, creating a convection current.

Radiation (Infrared) is the transfer of energy via electromagnetic waves. Unlike conduction and convection, radiation does not require a medium and can travel through a vacuum (e.g., from the Sun to Earth).

Thermal insulators are materials like wood, plastic, and air that are poor conductors of heat and are used to reduce energy transfer.

The change in temperature ($\Delta T$) depends on the mass ($m$) of the substance and the specific heat capacity ($c$).