Both my 5th and 6th graders do a separating mixtures lab. This is the 6th grade lab that can be found in Matter and Change by Delta Science Modules.
I set of the trays before the students come to the lab. It included a funnel, filter paper, pie tin, water, 2 stir sticks, salt and sand.
The students filled the cups about half way with water and stirred the mixtures. They made notes in their journal about what happened.
The students were amazed to see how the crystal reformed. I apologize for the bad picture, it was hard to get a close-up with my phone.