I just finished student teaching sixth-grade science. I did a few science demonstrations while teaching virtually! My students were learning about Force, Motion, and Gravity, so my demonstrations fit into these topics. The first demonstration I did was the Gravity Water Cup Drop demonstration. The SciGuys on YouTube do a great job explaining this demonstration. I used their video to create my own demonstration video for my students. I just recorded myself doing the demonstration, going between slow motion and regular motion. When doing demonstrations virtually, I always pre-recorded myself doing them and integrated them into my lesson plans. I was able to stop, ask questions, and replay portions of the videos. The students really enjoyed seeing me do the demonstrations. For my contact force lessons, I recorded myself pulling a laundry bag, pushing a box, dropping paper, and a book sitting on my table, and students thought about the forces involved in each situation. These were simple, but effective demonstrations! Hope this helps!