This topic sentence introduces the reader to the rest of the paragraph. I would expect the body of the paragraph to tell how heat energy travels and perhaps have an example.
The purpose of a topic sentence is to introduce and summarize the main idea of a paragraph or section of text. In the given sentence, "Heat energy travels from warmer objects to cooler ones," the topic sentence introduces the concept of heat energy transfer and specifically highlights the direction in which heat travels. It establishes the main idea of the paragraph or section, which would likely be focused on explaining concepts related to heat transfer and the movement of heat energy.
