Density Gizmo

With a Density Gizmo, students continued to deepening their understanding of matter, mass, and volume this week, 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. 

During our activity, we concentrated on Activity A focused on water, however students have access to Activity C, too, where they can experiment with the density of liquids like oil, gasoline, seawater, and corn syrup.  They can log on at home with the user name and password in the back of their planner. If a student moves on to the Activity C exploration, we'd love to hear their analysis, How does an object behave in different liquids?