## Thursday, November 8, 2012

### Density Gizmo

This week, with a Density Gizmo in Science, our students continued to deepening their understanding of matter, mass, and volume, and explored density. They first brainstormed objects that they think would sink in water and then those that would float, and formed a hypothesis for why the objects sink or float.

After that, they did a Gizmo warm-up which familiarized them with the virtual exploration by measuring the mass of objects on a scale, and measuring the volume of objects using water displacement in a graduated cylinder.

The essential question then focused their activity, How do mass and volume affect sinking and floating?

During the Gizmo, students filled in a chart with each object's mass and volume, and then whether the object would sink or float when placed in the beaker.  This is a sample of their chart.

 Object Prediction (sink or float?) Mass Volume Result (sink or float?) Ping pong ball F 3.0 g 36.0 mL Float Golf ball S 45.0 g 36.0 mL Sink Apple F 33.0 g 44.0 mL Float Chess piece S 40.0 g 80.0 mL Float Penny S 3.0 g 0.4 mL Sink Rock S 200.0 g 50.0 mL Sink

They analyzed their results and concluded that you could not predict whether an object would sink or float using the mass alone, because the mass of a ping pong ball and penny were both 3 grams and one floated while the other sank. Based on the volume alone, they concluded that you could not predict whether an object would float or sink, because the volume of a ping pong ball and golf ball were both 36 mL and one floated while the other sank.

However, mass and volume, when considered together could predict whether an object would sink or float. When an object's mass was less than the object's volume, the object floated.  When an object's mass was more than an objects volume, then the object would sink. Density refers to the mass found in a given volume of a substance.

These are third graders that I teach and they are taking it in like sponges! They even clapped when we said, "Today, we will be doing a Density Gizmo!" It doesn't get any better than that!