02. Convection

While conduction moves heat to food through the metal grill grate (and throughout the food itself), convection moves heat around food. As the fire heats air inside a closed grill, the molecules in the air move faster. Moving molecules take up more space than still ones, which makes the hot molecules rise. Air currents develop, circulating hot air toward the top of the grill, which forces cooler air down toward the fire, where it is heated, causing it to rise, and so on. Convection is not a primary method of heat transference in grilling (especially with no grill lid), but it does account for some of the cooking that takes place in indirect grilling, in which food does not come into direct contact with a hot grill grate or a radiating flame.