Answer :
Final answer:
Water heated from below uses convection to distribute the heat, while water heated from above uses conduction. Convection involves the movement of warmer, less dense water rising, while conduction involves heat transfer through direct contact.
a. Conduction; Convection
Explanation:
Water heated from below distributes the added heat by convection, whereas the still surface of water heated from above distributes the added heat by conduction. When water is heated from below, as in a pot on a stove, the water at the bottom of the pot heats up, expands, becomes less dense, and rises. This creates a current within the pot as the cooler water descends to take its place, forming the process of convection, which efficiently mixes the water and distributes the heat. In contrast, if water is heated from above, the heat is transferred to the water directly beneath the heat source through conduction, without initiating a current, because the heated water does not become less dense than the cooler water below it.
