answer:
warmer objects to cooler objects in liquids and gases
Step-by-step explanation:
The natural convection is a process, in which the fluid movement occurs from heat transfer. When a fluid is warmed or chilled, its density changes and the buoyancy effect create a natural flow in the affected region, which makes itself the rise of hotter fluid and the fall of cooler fluid: hence, energy transfer from hotter area to colder area and such process is repeated as long as the temperature variation in fluid exist.