Phenomena is only as effective as the unit it is embedded within. The questions that students raise should be directly connected with the core ideas that you want the students to engage with using the science and engineering practices. For example, we all love seeing a volcano model explode - but this does nothing to connect students with the real world phenomenon that helps us to understand the natural and geologic mechanisms that cause the formation of landforms due to volcanic activity.
Please keep in mind when thinking about choosing which phenomenon to anchor your science units or lessons with - that students should be able to dig deep into the phenomenon to uncover some ideas that are core to science. Phenomena are commonly thought to be the "ewwwww, weird, oh man!!" kinds of traditional science demos which (while still really fun for teachers & students) are not always academically productive. Phenomena should drive units and keep students working to "figure out" rather than "learning about."