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Easy STEM Challenge: Build a Boat

It is the title photo with an aluminum foil boat and gram weights

Phenomena for Building a Boat STEM Challenge

First of all, what is phenomena?  In science, a phenomenon is simply an event or situation occurs.  The event causes students to wonder about it (I wish the NGSS would just do away with the word phenomena!).  Before building a boat there are several situations that can be shown to students.  Use a photo such as the one below.

to show students a large pan can float on top of water

I put this big pan in my swimming pool and took a picture of it floating.  Project a similar photo and ask students to discuss in groups what this pan is doing or how is something like this possible.  Better yet, fill a sink or have a large plastic container filled with water.  Then, show the class a large pan and ask them what they think will happen when your place in on the water.  Most often they think it will sink.  What would happen if the pan was turned over, put in on edge, etc.?

Another activity I like to do is place an unopened can of diet soda in a clear container filled with room temperature water (I keep a spare aquarium in my lab and find it useful for many activities).  Diet sodas will float!  Again, ask students what they think will happen before you put it in.  Most students will wonder how this is possible.  They may also ask if different flavors or regular soda cans can float.  Have those on hand.  Hmm, the cans are the same size and have the same volume.  How can this happen?  In this case, regular sodas have more dissolved sugar in them, making them denser.

Archimedes Principle

Shows archimedes in a tub the illustration shows archimedes principle

Archimedes Principle is a law of buoyancy.  It was discovered by Greek scientist and inventor, Archimedes.  Buoyancy is the ability to float in a liquid.  It is based on the amount of water that is displaced by the object.  If an object displaces more water than it weighs, then it will float.  Something that has a large surface spreads the weight of the object over a greater area.  The story says that Archimedes’ discovered this law while taking a bath.  The story Mr. Archimedes’ Bath by Pamela Allen is a good book to read to your class.  It is older, thus costly.  Check to see if your library has it.  If not there is a YouTube of someone reading the book.

Ask students what they do if they want to float in a pool.  They will lay on their backs with their arms and legs spread out.  Why do they do that?  So that their weight is spread out more evenly.  Often they will take a big breath.  This makes them less dense.

Build a Boat Challenge

There are so many ways that students can build a boat.

With first and second graders, I like to do a basic lesson on floating and sinking in small groups.  I give them a variety of items and let them take turns putting them in a container of water.  Do objects float or sink?  Why or why not?  What are the properties of the materials that float?  Next, I give individuals a sheet of 12 x 12 foil and ask them to build a boat that will hold the most weight.  Since students are also practicing counting by 5’s, 10’s, and 25, I have them put their boat in a pan of water and add gram weights.  This can be individualized by giving students a pile of weights with the number they need to practice counting by.  While other students are waiting for their turns, they can count too.

Ask them to observe what is happening to the boat as they add weight.  It starts to sink.  What about if they take weight out?   The boat rises back up.  Does the shape of the boat matter?

More Boat Building Ideas

Another way to make a boat is to test different objects/materials that they might use to make a boat to see if they float.  Ask students to collect items from around the house.  Here is an example of items they might test.  Styrofoam and modeling clay are good too.

items collected to test for boat building

Older students can use different materials to make more elaborate boats and then test to see which boat can hold the most weight.  For this experiment, I let them pick the materials they want for the build, but give them a constraint such as size (example: the boat must be less than 8″ at its longest point).

Other materials that you can use instead of gram weights to put in the boats are coins (just make sure everyone is using the same coin), large paper clips, math manipulatives (think Unifix cubes, plastic pattern blocks, etc.).  I had one teacher tell me she used candy kisses at Halloween time!

I have also given students straws, toothpicks, and/or coffee stirrers, and asked them to build a boat with a sail.  Then I set up a large, long pan or a small kiddie pool.  I have them place their boat in the water, turn on a fan, and see if the boat can sail across the container without sinking.  It’s a great way to talk about wind energy too.

Improving the Boat Design

Whatever boat building challenge the students do, they should always do at least one redesign.  The good news is, is that they almost always want to do this.  Students put together everything they have learned and try to improve their boat.

Order of the Lesson

First and foremost, do what you are comfortable with.  You know what your students need.  If strictly following the Next Generation Science Standards, show them and discuss the phenomenon, build the boat, and then, talk about Archimedes Principle.  Here is a video about buoyancy, How Do Ships Float.  After students learn more about what makes things float, have them do their rebuild.

Click below if you would like access to our Float Your Boat STEM Challenge.

link to float your boat stem challenge in our TpT shop

If you are interested in another simple challenge read Building with Bricks Simple STEM Challenges.

And remember,  it’s all science!


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