Science Smarts: Sink or float

By Patty Rooks on January 24, 2026.

I have had some fun this week exploring buoyancy. This is a hard scientific concept to understand just by reading about it I feel, so hands on is the way to go. Give this activity a try and make it into a classroom challenge! Let’s get started.

*Remember to ask an adult before doing this experiment.

Materials

– One piece of aluminum foil (30 cm x 30 cm piece)

– Tub of water or a sink

– Weights (metal washers, paper clips)

Procedure

1. Think carefully and design your boat. Use the piece of aluminum foil to make your design. Remember, this is your design. It does not necessarily have to look like a modern ship – use your imagination.

2. Place the boat on the water and add metal washers to the boat until it sinks.

3. Think about how you could improve your design.

4. Try it again if you wish.

5. Make it into a design contest if you are in a classroom – you will be amazed at the creative designs!

What is going on?

The scientific concept that can be applied here is displacement. Let me give you an example. When you sit in the bathtub, the level of the water rises. It increases because your body occupies a space that was previously filled with water. When you sat down, you pushed away (or displaced) an equal volume of water. When you displace water, you generate an upward force that is equal to the weight of the water you “pushed out.”

This is also what happens when a ship floats in the water. A ship’s hull displaces water. It is designed to displace enough water to keep the entire boat afloat (we hope)!

Last call before the southeastern Alberta Regional Science Fair Button Contest closes – deadline has been extended to Jan. 31. Your button design will be featured at the science fair this year and you will win a cash prize. Visit the Praxis website at praxismedhat.com/sciencefair for all the details.

Patty Rooks, senior scientific consultant Praxis Science Outreach Society. Praxis is located in the Community Futures Entre Corp Building at #202 556 Fourth St. SE, Medicine Hat, Alberta, T1A 0K8. For all your science needs, please email praxis@praxismh.ca.

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