The differences between the uses of future simple (will) and going to are very close, and they sometimes overlap. Here's a match-the-uses worksheet which compares the distinctive uses oıf both tenses. In the worksheet, there are two short quizzes with sentences which demonstrate different uses of will and be going to.
I suggest you pair the students and cut the worksheet in half. Then, each student can check his partner's quiz and learn more by explaining their answers to each other.
There's also a QR code answer key included.