If two media at different temperatures contact each other, they are exchanging energy. In thermodynamics, this energy transfer is called heat transfer. Actually direct energy exchange is realizing at the collisions of atoms and molecules of the hotter media with atoms and molecules of the cooler media. This simulation demonstrates a simplest example kinetic energy transfer during a single collision. The initially hotter orange particle collide the cooler blue particle. Run the simulation and note the initial and final kinetic energy values. Use the play back control below the simulation for your observation to be more carefully.