Explore why objects float or sink

Make a prediction and investigate

Observe the initial object and liquid. Change one available control, and record whether the object floats, sinks, or changes its position.

Controls in the actual lab

• Density: starts at 0.85 g/cm³; available range 0.4–1.4 g/cm³.

An object floats when it is less dense than the fluid. Denser than the water, it sinks.

Discuss the evidence

Compare the object and its surroundings. Explain why naming the object’s size alone is an incomplete explanation.

Try it beyond the activity

Describe a comparison that would help distinguish the effect of the object from the effect of the liquid.

Record your thinking

Sources and limits

This companion uses the published Buoyancy activity and its learning guidance. Review any original sources linked there. It is a discussion plan by Lesson Worlds, not a scored assessment, a standards certification, or evidence of learning gains.

Use this activity with a learner

Families and educators · choose by prior knowledge

Learning goal: An object floats when it is less dense than the fluid. Denser than the water, it sinks.

Before you begin: Read the controls for Density. Make one prediction before changing a setting.

Check understanding: Ask for one observation, the evidence that supports it, and a question to investigate next.

A simulation simplifies the real world. Explain which conditions stayed fixed; a successful run alone does not demonstrate mastery.

Activity and guide by Lesson Worlds. About the platform.