Sponge activities are those activities which soak up time (like the last two minutes of class when students are getting ready to move). Industrial strength sponge activities are those sponge activities which encourage critical thinking and have a connection to the course content. I have used several different sponge activities over the years, from a simple writing prompt to summarize the work done in class to playing an interactive game. I am always on the lookout for new ones.
Currently, in my Geometry classes I use SET Game to promote inductive reasoning and Guess the Colorsto promote deductive reasoning. I classify both of these games as industrial strength sponge activities because they support the work done in our Reasoning and Proofs module. My students are usually interested enough to stop and play.
What sponge activities do you use in your classroom? Can they be transferred to other subjects? Are they industrial strength?