Question

In what direction does heat flow? Why do particles of matter transfer thermal energy in this direction?

Answer 1

Heat flows towards colder objects.

Answer 2

heat goes downward, cold goes upward.

Answer 3

Nuts to that answer. Heat is energy of vibration, rotation, or translational movement of molecules and atoms. The more heat, the more movement. Temperature is a measure of the average kinetic energy of these molecules.

Now a hot object, with all this molecular motion, when it comes into contact with other molecules, they collide, and energy is transfered to the "slower" "colder" molecules making them move faster. thus, heat "flows" from hotter to colder. Heat flow is really energy flow, from the more vigrous movers to the slower or stationary movers, regardless which one is upward, or downward.