Robbie and I selected some coins and some small plastic Lego accessories and placed them in a water-filled ice cube tray. He observed which items floated and which sank. He then told me that the floating items would freeze at the top and the sunken items would freeze at the bottom.
After a few hours in the freezer, we removed the tray and checked to see if his predictions were correct. He even noted that some of the "floaters" were actually sticking up out of the ice.
We emptied the ice cubes into a plastic bin to begin our melting process. A few items came out with a pull or two.
Robbie wanted to pour some warm water on the ice cubes to make them melt faster. He did this a bit at a time so that he could focus on just a few cubes at a time.
At my suggestion, he tried breathing on a cube to see how that would affect the melting process.
Overall, this was a fun and easy project. Robbie really wants to do it again and I am more than happy to oblige.