Which of the following statements about the flow of heat energy is true?

Heat energy flows from a warmer source to a cooler source due to the second law of thermodynamics, which states that heat naturally flows in this direction unless work is done to reverse that flow. This principle underlies many fundamental concepts in thermodynamics and is observable in everyday situations. For example, if you place a hot cup of coffee on a table, heat will transfer from the coffee (the warmer object) to the surrounding air and the table (the cooler objects) until thermal equilibrium is reached.

The other statements presented do not align with the established principles of heat transfer. Heat can indeed move through solid materials as well as liquids and gases, which are known as conduction, convection, and radiation, respectively. Thus, asserting that heat only moves in solid materials is inaccurate. Additionally, the movement of heat is universally understood to be from hot to cold rather than the reverse. Thus, any implication that heat could flow from a cooler to a warmer source contradicts the basic laws of thermodynamics.