Lesson 3: Particles in Motion – We learned that heat is the movement of thermal energy from a region of higher temperature to a region of lower temperature. Materials are said to be in thermal equilibrium when the temperature of materials that are touching are equal. Next we learned about the 3 types of heat transfer: conduction, radiation, and convection. Conduction is the transfer of thermal energy due to collisions between particles of matter. Radiation is the transfer of thermal energy by electromagnetic waves. Convection is the transfer of thermal energy by the movement of the particles from one part of a material to another.