This is a GREAT activity to get your students' brains going. Most of them will probably whine about how difficult it is, but the activity truly forces students to make connections and learn material at a deeper level.
My word splash uses 40 vocab words from the Ecology unit that I teach to my Biology class. You can easily change this to fit any vocab for any unit. Students have to pick words and group them, explain why they are grouped, and then choose and explain a bonus word that fits into the category as well.
There is no one right answer to this activity. You will see some really neat creativity, and you'll also be able to pinpoint misconceptions.
Here is the link to the video I use for instructions (also listed on the worksheet): https://www.youtube.com/watch?v=iz89hdqMFVI.
Again, feel free to modify as needed! It can be adapted to any class, any grade level, any subject!