If I have two candy bars that are the same size, I am sure the kids can pick which one will float and which one will sink. And they will probably be right. But what happens when I use a really big 3 Musketeers bar, and a really small Snickers bar? I’ll try it tomorrow and let you know. But, I will be very surprised if they understand that with density, size does not matter. Only “crowded-ness” matters.

### Monthly Archives: April 2013

## Chocolate density

The easiest way that I have found to teach students the concept of density is to talk about how crowded a place it. Identify a section of your classroom. As 1 student to stand in this area. Ask if it is crowded. Then add a second child, again asking the students if it is crowded. Double the number of student until you either run out of space or students. At some point the students will agree that the space is crowded.

We discuss how “crowded” a Snickers (R) bar is. Is it more “crowded” than a 3 Musketeers bar? As scientists we use the work dense instead of crowded. We can test how dense something is by seeing if it is more dense than water. If it is less dense than water it will float on water. If it is more dense than water will sink. And if the density is the same as water it will flink — which is hovering.

This is a science experiment the kids will want to try again and again. Now is the perfect time to introduce the concept of variables. Is it important that both candy bars are the same size? (No.) Is it important that both candy bars are unwrapped? Yes.

More on this later. For now, I’m going to eat a Kit Kat then go to bed. See you tomorrow.

## Welcome NSTA Elementary Extravaganza Participants!

It was wonderful to see you in San Antonio. It will be such fun to teach our students science using food.

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