🔹 9.1 Thermal Energy and Heat Transfer in Solids
1. Thermal Energy
Thermal energy is the change in internal energy of a substance, which includes the total
kinetic and potential energy of its particles.
2. Heat Transfer in Solids
In solids, heat is transferred by:
o Vibrating molecules: Particles vibrate and pass energy to neighboring particles.
o Free electrons (in metals): Move freely and carry energy efficiently.
3. Thermal Conductivity
A material’s ability to conduct heat is known as thermal conductivity.
4. Factors Affecting Heat Transfer
Type of material (thermal conductivity)
Cross-sectional area
Length of conductor
Temperature difference across the solid
5. Conductors and Insulators
Good conductors: Copper, aluminum
Poor conductors (insulators): Wood, rubber, plastic
6. Practical Uses
Good conductors: Cookware, radiators
Insulators: Pot handles, building insulation
🔹 9.2 Conduction
Conduction is the transfer of heat through a solid.
Insulation materials (e.g., wool, foam) reduce heat transfer by slowing conduction.