Sink or Float? A Wet Science Experiment

As a child, there’s nothing more fun than doing a hands on easy science experiment. And one of the easiest and most accessible supplies comes from your kitchen sink – water! Here’s a fun and exciting kids science experiment that you and your child can do together to teach them all about what stays afloat, and what sinks to the bottom.


Gather a pitcher or bucket, and fill it with water. If you are doing this with younger kids filling the bathtub or kiddie pool might work better. Once you have this, collect toys that your child has of different shapes and sizes (different densities, really, but he or she might not understand that yet). Try to gather toys made of different materials, too, such as wood, plastic, and metal. For older children, have them use a notebook or piece of paper to record results.

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The Experiment

Begin with your child placing one of his or her favorite kids toys in the water. Watch their face as it sinks or floats, and ask them about the result. Then have them mark it down on paper, if they are older (it can be something as simple as “ball – floats”). Then proceed with the next toy, making sure that your child understands the result and is marking it correctly. Proceed to use all of the toys in this manner, each time recording the event.

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Once your child has gone through the toys one by one, ask them if they would like to try any of them again. Let your child experiment with putting in two at a time, or all at once. Some will float, and some will sink, and ask them why they think that is. Make sure to point out to your child the differences between the kids toys that stay afloat and the toys that don’t, and have them predict what will happen with the next toy. Any guess is a good guess.

The Results

After you have finished collecting the information, have your child go over the results with you, and put each toy in one of two columns, ‘sink’ or ‘float’. Now you can begin explaining the concept of buoyancy, or why an item might stay above the water. First go over density, but in a simple fashion. Explain that wood items, or even plastic items, hold different material that allows them to stay above water. Try to explain that metal is the opposite, and will generally always go under.

Real World Predictions

Once they understand why an item might sink or float, pick items around the house or even in nature that you can ask them about. For example, ask your child if they think a tree would float in water. Remind them that a tree is made of wood, and that wood objects generally stayed afloat during your cool science experiment. Then ask them if they believed that a car would float or sink, and once again remind them that metal objects generally sunk under water during the experiment. This will get them thinking about how to apply the science project to the world around.

Get Wet!

The experiment doesn’t have to end here. Next time you go to the pool together, or even give a bath, remind your child about all of the things they learned, and see if they don’t start experimenting again. And don’t be afraid to get a little wet!


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