Have you ever wondered how a submarine works? How does it dive and then surface again? The key lies in the ballast tanks which can be alternately filled with water or air. When they are filled with air, the submarine is less dense than water, so it rises to the surface. When they are filled with water, the submarine is more dense than the surrounding water and dives. Check out this great article on How Stuff Works that explains how a submarine works in greater detail with a nice picture.
A couple of months ago my husband took Tommy, our then four-year-old, on a tour of the USS Blueback. Since then, Tommy has been hungry for any information he can get about submarines. One morning he woke up so anxious to learn more that we spent our entire homeschool day on submarines. We read Submarines, looked up links from the book, played Battleship, and did this awesome science activity to see how a submarine’s ballast tanks work.
Total Time: About 5 minutes
Safety Concerns: None.
Materials You Need:
A tall vase, bowl, or pot 3/4 full of water
An empty soda can
- Place one end of the tubing inside the soda can.
- Fill the soda can with water, making sure no air bubbles are trapped inside.
- Place the soda can in the vase. If it doesn’t sink, fill it with more water and make sure no air bubbles are trapped inside.
- Once the soda can sinks, blow into the plastic tubing. Watch as the air travels through the tube into the can, making it surface!
As air flows into the can, water is displaced, and flows out. This makes the soda can less dense than the surrounding water, which is what makes it rise to the surface!
Word to the wise: Once you are done blowing into the tubing a siphon is created, meaning you will get a mouthful of water if you are lower than the water level. My son actually loved this and thought it was a super fun reward, but if you don’t want a drink, make sure your end of the tubing is higher than the water level!
We got this idea from The Usborne Book of Science Activities, which is totally jam-packed with hands-on science fun for kids of all ages.
How Can I Learn More About Submarines?
- Go on a tour of a submarine if you live close to one. Here in Portland, we have the USS Blueback at our science museum!
- Read Submarines (buy it here) and check out the Usborne quicklinks page that go along with the book to watch video clips, listen to sounds that a submarine sonar operator might detect, and build your own submarine!
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