Formative Assessment

Do students think that very tiny things have weight?

Observe students as they work and listen as they make meaning to find evidence of their ideas about whether pieces of matter too small to feel, do actually weigh something.

As you interpret students' comments, listen for these ideas that commonly arise:

• If you can't feel it, it doesn't have weight.
• If you can see it must have weight.
• A tiny creature (a flea) might find this minute piece of clay weighs something.
• If you gather the tiny pieces together, you get a ball of plastic modeling clay that will weigh 8 grams.

The teacher recognized the student was in the process of developing the idea that tiny things have weight. Her next step was a question, "I heard you say that you don't think tiny things have weight but if you squeeze all the little pieces of plastic modeling clay together, you'll have a piece that weighs a gram. If the tiny pieces don't have weight, where do you think that weight comes from?"