We began saving containers of all shapes and sizes, washing them out and putting them into a plastic box. Some of these were traditional sizes, others were more unusual sizes, like a 2.78 quart jug or a 30 ounce jar. Once we had a significant stash, the boys pulled the box onto a porch, grabbed a water hose and set to work.
We talked about cups, quarts, and gallons. My homemade manipulatives are actually much better than the real thing because the some of the containers are different shapes, but the same size. We discussed how something tall and thin could hold the same amount as something short and wide.
They are having a wonderful time discovering how many cups are in a gallon, and how many quart containers they can fill from a half gallon. I'm loving the learning that is taking place!
A few final photos - because they did not stay on topic... They explored floating and sinking, water power, and a few other fun things!