The transfer of heat by the physical movement of material is called convection.

Here's why:

* Conduction: Heat transfer through direct contact between molecules. Think of a metal spoon getting hot when you stir hot soup.

* Convection: Heat transfer through the movement of fluids (liquids and gases). Think of boiling water where hot water rises and cooler water sinks.

* Radiation: Heat transfer through electromagnetic waves. Think of the sun warming the Earth.

Convection is the only method that involves the actual movement of the material itself to transfer heat.