The statement that best illustrates the scientific definition of heat is: "To make tea, she applied heat to a pot of water until it boiled."
In scientific terms, heat refers to the transfer of thermal energy from one object or substance to another due to a temperature difference. In the second statement, the focus is on the transfer of energy (heat) applied to the pot of water, leading to its boiling. The first statement incorrectly uses "heat" to compare the thermal energy content of two different substances (soup and ice cubes), which does not align with the scientific definition.