Due to limited materials, I set this up as a stations lab, but since this is an editable download, you can change the "Station" title to task.
Students should already know that water is a polar molecule. Quickly introduce that polar molecules mix with other polar molecules due to charge satisfaction and let them figure out the rest. I take my time with this and let it last a full 40 minute period, but you very well could do this in 20 minutes. My students really got a kick out of the Aqua Sand.
Hint: I homemade mine, using colored sand from Amazon and waterproof camping spray. I made 3 pounds for a quarter of the price to buy Aqua Sand at the store. Spray and stir in a disposable aluminum pan.