Final answer:
In J.S. Bach's Cantata No. 140, the energetic instrumental idea that recurs is known as a ritornello, a common musical structure used in baroque compositions.
Step-by-step explanation:
The energetic instrumental idea that recurs several times between the vocal statements in the first movement of J. S. Bach's Cantata No. 140 is known as a ritornello. The ritornello is a recurring musical theme that frames the solo sections of the movement, often played by the full orchestra in baroque compositions. It not only creates cohesion within the movement but also provides contrast to the vocal sections, enhancing the overall musical narrative.