Sink or float? STEM session plan

Playing with water is one of the most fun activities you can propose to young students. Sink or float is a fun science concept for students to explore.  Setting up “sink or float” working stations will invite students to experiment and explore how and why different objects sink or stay afloat when placed in water.

Sink or float

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Content: Technology: buoyancy: sink or float, properties and characterization of materials. Math: classifying the materials

Skills: Students will learn which objects sink and which float. Predicting, experimenting, observing, analysing.


You can find plenty of resources online on the topic. Also, if you’re in the mood for something more serious, you can check out these books


Background information:

Before getting their hands wet, gather students in a group and tell them that they will be learning about sinking and floating. You may read aloud  “Things That Float and Things That Don’t” or “Who Sank The Boat” to the class.

Define sink as the action of an object when it becomes submerged in a liquid. Define float as the action of an object when it sits on the surface of a liquid.

Tell students that lighter objects are more likely to stay on the surface of the water and heavier objects are more likely to sink to the bottom of the tub.

Activity plan:

Collect an assortment of classroom materials and have the students predict whether they will sink or float in water. Have children describe their prior sink and float experiences.

The students shall take turns testing each item so everyone gets an opportunity to drop an item into the water. Continue predicting and testing each item until all are tested.


Prepare the recording sheet for each student. The recording sheet will show the image of each object used for the experiment. Based on their observation, students will circle the image of each object that floats and cross off those of the objects that sink.