Object: An ice cube tray that you can fill slowly with water from a pitcher.

Good morning, boys and girls. How many of you have ever made ice cubes? [Let them answer.] Very good. Almost all of us have had to fill the ice cube tray with water, so that there would be enough ice the next time we needed some. I think it is fun to do this and see how the water fills each cube spot with the same amount of water that will soon turn into ice.

Let me show you what I mean. [Begin to fill the tray, pouring all of the water into one place or cube.] Did you notice that I poured all of the water into one spot, but each little space got the same amount of water as the one I poured it into? That is called sharing. The one space did not keep all of the water so that it could be a great big i…