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Sink or Float Activity

We don’t always realize how different shapes, sizes, and weights of objects will react on different surfaces. When it comes to water, it’s amazing how something as heavy as a huge boat can stay afloat without sinking underneath! What makes an object sink, or float?

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Activity PDF

Get the kiddos thinking and add a little splash!

This is an easy, interactive activity involving very little preparation. Gather the children to sit in a circle on the floor, and you can use ordinary, everyday classroom objects that are waterproof. You want to make sure that you are all doing this in an area of the classroom that is open, spacious, and okay to get a little wet! Have some towels or paper-towels handy for minor water drips. Having the children predict what will float and what will sink will also show then cause and effect with what happens. Plotting this on the chart paper help the child visualize their results and help understand why their prediction is right or wrong.


  • Basin or bin a small filled with water

  • 1 set of sink and float vote cards per child (see printable)

  • Select a few, waterproof items used every day in the classroom

  • Ensure that the number of objects equals at least the number of children participating at least one as they will be taking turns!

  • An easel with Large chart paper

  • Markers

Learning Outcomes




Physical Science


Observe, describe and compare properties of matter and how they change


Step 1:

Have the chart upright and easy to see, with a T-chart labelled “sink” and “float” in their own columns.

Step 2:

Place objects and tub of water in the middle of the circle.

Step 3:

Teacher should sit on a chair next to the chart to easily write on it , with the children seated on the floor with their vote cards in a circle around the tub. Make sure everyone can see both the tub and the chart.

Step 4:

Start with the child next to you. Have them come to the middle of the circle and pick an object from the pile. Have them take a moment to touch and look at the item, and pass it around the circle so each child can have a look. Let it return to that same first child.

Step 5:

Children make a guess with their sink or float vote cards on the floor in front of them. They are to decide if that object will sink or float when placed in the tub. Whichever vote card they place face up will be their guess.

Step 6:

Once everyone is ready with their guess, have the child place that object in the water. Let children watch what happens. Make sure everyone can see!

Step 7:

Record on the chart what happened - did the belong in the sink category? Or float? Write the name of the item under the correct column.

Step 8:

Proceed in order with the next child until all the items are gone!

Step 9:

Discuss findings, find things in common with everything than sank, and everything that floated. This is a fun, interactive group conversation where the children can collaborate their findings and ideas!

Playful Questions

  • Can you think of things that float on water?

  • How about things that sink in water?

  • What makes something float?

  • What makes something sink?

  • What if two things are the same but one sinks, and one floats? (Like a paper plate, and a regular plate?) Why is this?

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