When the stove is first turned on heat is transferred first by conduction between the element through the bottom of the pot to the water. However, eventually the water starts bubbling - these bubbles are actually local regions of hot water rising to the surface, thereby transferring heat from the hot water at the bottom to the cooler water at the top by convection. At the same time, the cooler, more dense water at the top will sink to the bottom, where it is subsequently heated.
Hot-air balloons use convection in order to rise into the air. The air inside the balloon is heated. As the hot air rises, so does the balloon. For the balloon to descend, the air in the balloon is cooled or allowed to escape.
LAND BREEZE AND SEA BREEZE.
In a convection cycle hot air rises and cool air falls, the freezer is at the top so that air cooled by it falls down the sections of a refrigerator and this type of design helps maintain a lower temperature at the top (for ice creams and ice cubes) as compared to that at the bottom (vegetable) section.
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