• Some objects sink in water while others float.
• Objects that are more dense are packed with more particles.
• Less dense objects take up more space with fewer particles.
• Relative density can be compared using water as a reference point.

EXTENDING THE DISCUSSION
After the observational question, randomly call on one or more students to share what they or their partner answered. Then ask the class, “Did anyone notice…?” using the suggestions above or anything else you’ve noticed.

• Why do some heavy objects float while lighter ones sink?
• Can two objects of the same size have different densities?
• How does mass affect whether something floats?
• Do gases and liquids also have different densities?
• Can density change if you cut an object into smaller pieces?

EXTENDING THE DISCUSSION
After students have shared what they notice, ask the class, “Did anyone wonder…?” using the suggestions above or anything else you might think is interesting or relevant to the lesson.

To the observational question, What does it mean for something to be more or less dense?

LOW-LEVEL

If something is more dense, it sinks. If something is less dense, it floats.

HIGH-LEVEL

If an object's relative density is more dense, it has more particles packed into a small space. If an object's relative density is less dense, it has fewer particles spread out.

RESPONDING TO RESPONSES
Emphasize and celebrate each student’s use of the key vocabulary to support a culture of “no wrong answers.”