To do this activity, I gathered a bunch of small plastic toys and put them in a glass bowl. I filled the bowl with water and put it in the freezer. I forgot about it for about a month until one really hot day.
When I finally remembered the activity awaiting us in the freezer, I gathered the supplies needed...I put the bowl of ice and toys on a tray along with a hammer, salt, cup of water, water dropper, dull knife, etc.
The girls got to work immediately! They loved hitting the ice with the hammer. They poured a whole salt shaker worth of salt on the ice to help it melt, and they had fun dripping water onto the ice with the water dropper.
They enjoyed this activity so much that they immediately wanted to do it again. We put the toys back in the bowl, added water, and put it in the freezer. It was ready the next day, and they had a super time again. We are on vacation now, but I'm sure we'll do this activity several more times before summer's end.