Raise your hand if you’ve ever sat on your suitcase to zip it up. No one is here to judge you. I know I’m not the only one.
When I get to the airport, I anxiously place my suitcase on the scale and pray I’m under the 50 pound limit. So far, I’m at a 100% success rate – thankfully.
Now that you know my travel habits…
I give you this word picture because it directly relates to how I talk about density with my middle school students.
The concept of density is kind of tough to grasp. It’s very concrete, but it’s also very abstract. Do your students grasp it?
Density is defined as the degree of compactness of a substance. Mmmmmkaayy….? Your sixth or seventh grade student can’t really wrap their head around that.
You might try and explain it by saying it’s the amount of stuff in a certain space. Give them two objects that are the same size and are drastically different in mass. Closer. That is a little more concrete.
What about a suitcase?
You’re going on a trip with a friend … let’s say to Bora Bora. The airline will only let you bring a standard carry on suitcase. Both of your suitcases are the same size. In fact, they’re identical.
You are an overpacker. The kind of person I talked about earlier. Where you have to sit on the suitcase to zip it.
You pack 14 shirts, seven shorts, three jackets, two different curling irons, 7 pairs of shoes – including rain boots… just in case, and three bathing suits, and a few other things you need for your trip.
Your friend is a light packer. For the same trip, they pack six shirts, two pairs of shorts, a hairbrush, a jacket, a bathing suit, and two pairs of shoes.
Are you still with me? Here’s what we’ve been building to.
Whose suitcase is more dense?
Each one of those items is now a piece of matter. Remember… both of your suitcases are the same size. Which one is more dense?
Yours. The one you had to sit on to zip! It’s more dense because it has more matter in it!
The suitcase with more matter has more mass and is more dense. It’s going to be heavier too. There is less air in between the matter. It makes your stuff more compact and less likely to move around inside of your suitcase.
In contrast to your friend’s suitcase, there is less matter. The suitcase will be lighter, and there is more air or space between the matter. It’s less dense.
Students identify with this story! They either are one or know both types of packers. By capitalizing on an idea they are familiar with, you can easily illustrate the abstract concept of density in your middle school science class!
For a great inquiry experiment about density, check out this video and supporting materials on the Teaching Channel!