Homeschool Science: A Paper Plate Density Model

I was reviewing the kids' homeschool year, as I like to do in the summer, when I was reminded of how much we all enjoyed last summer's density study. Taking a closer look at that, and wondering if a brief review might be in order, I realized that I never showed you one of the fun, hands-on density activities that we did. Silly me!

This activity, a paper plate density model, actually would work well to repeat this summer if we did do a short review, since it focuses on illustrating the way that the number of molecules within a specific area of a substance dictate that substance's density. Since the kids have studied atoms and molecules much more extensively this year than last, repeating this activity would add context to their understanding of how atoms and molecules work.

For this activity, you will need:

• paper plates. I usually make a point to avoid crafting with them, and you could use cardstock for this, but frankly, paper plates are kind of perfect here, and that's why I used them.
• dot markers, stickers, or a bottle cap to trace circles. I bought a set of these Do-a-Dot markers SO many years ago, for use when the kids were both preschoolers, and they still work great! We don't use them very often, but we've certainly gotten our money's worth on them over the past at least six years, and again, they're perfect for this project.
• yarn. I pre-cut the yarn into six-inch lengths.
• hole punch.

1. Have the kids work as a team to put circles onto several paper plates, with the one rule that every single plate must have a different number of circles on it. No two plates can have the same number of circles. Depending on your kids, this may really test their teamwork skills!

2. Review your definition of density, which should be something along the lines of "Density is the relationship between mass and volume. In objects with the same volume, those that have more mass will be more dense."

You can explain the dots on the paper plates either as a representation of each plate's mass, or as a representation of how many molecules of a similar mass are in that plate. Either way, the concept is that the volume stays the same, but the mass of every plate is different.

3. Challenge the kids to arrange the plates from least dense to most dense:

4. If you've done the density bottle experiment already, the kids should have a good visual memory of the concept that less dense substances sit on top of more dense substances. Tell them that you'll be hanging this paper plate model, and ask them to lay out the plates in the order in which they should be hung. They should put the least dense substance at the top, and the most dense at the bottom.

5. Once the model is laid out correctly, then the kids can bring their fine motor skills out to play! They should punch a hole at the top and bottom of each plate, tie on the yarn--

--and then tie the plates to each other in the correct order.

For extra enrichment, and especially if you've been studying elements or have already done several density demonstrations with real substances, the kids can research and print out images of substances that will mimic their density model and glue them to the backs of the plates so that when the contraption hangs, there's the model on one side and a visual illustration on the other side. The top plate, for instance, can have a picture of a helium balloon or whatever, and the bottom plate has, like, uranium or something.