ocr: CONVECTION The physical up-welling of hot matter, thus transporting energy from a lower, hotter re- gion to a higher, cooler region. A bubble of gas that is hotter than its surroundings ex- pands and rises. When it has cooled by passing on its extra heat to its surroundings, the bubble sinks again. Convection can OC- cur when there is a substantial decrease in temperature with height, such as in the Sun's convection zone.
