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Marshmallow Bridge for the Win!

Have you ever tried Marshmallows in the STEM Lab? I have! And I have tips for you-especially with this Marshmallow Bridge STEM Challenge!

Marshmallow bridges! Oh my, the first time we used marshmallows as a building material was such a learning experience! I have some tips for you sprinkled throughout this post that will help you breeze right through a STEM Challenge with marshmallows!  

It’s the famous Marshmallow Bridge project! Ooey-gooey marshmallows, in fact.

Building a Bridge in STEM Class- This fabulous STEM activity is to build a bridge using marshmallows. The bridge must hold weight and be a specific length. Blog post with tips about using marshmallows.

In this post, for your convenience, you may find Amazon Affiliate links to resources. This means that Amazon will pass on small percentages to me with your purchase of items. This will not create extra costs for you at all! It will help me keep this blog running!

We have tried different versions of the Marshmallow Bridge!

Since we had no idea what to expect with this challenge it was great fun for everyone. Seriously.  I think the STEM Lab is the most fun when I don’t even know what is going to happen. Kids love it when something surprises me!  We have repeated this project several times over the years and I have it separated like this:  

  • The Original
  • The Plastic Span
  • Blueprints

TIP: Repeat projects you enjoyed with your class. The second time is even more amazing than the first time since your students will have grown as engineers and you will have a different way of presenting the topic.

The Original Marshmallow Bridge

Building a Bridge in STEM Class- This fabulous STEM activity is to build a bridge using marshmallows. The bridge must hold weight and be a specific length.
Building a Bridge in STEM Class- This fabulous STEM activity is to build a bridge using marshmallows. The bridge must hold weight and be a specific length.

The first time we tried a bridge I wasn’t sure what to use as the “span” section for the structure. I wanted an opening that would be 5-6 inches because I did not think these bridges could be very long.  

Pushing two tables close together is the answer, but my tables are very heavy. I decided to try something lightweight and movable (at least more movable than my 9-foot-long tables)!          

You can see what we used in the photo above. Tissue boxes!  I had plenty of those! I set up two boxes on each lab table and taped them in place. Each team had their spot to try their bridge.  

Now to the dilemma of using marshmallows! If you buy the name-brand kind of marshmallow you are likely to find that the marshmallows are very fresh. This is ideal for making hot chocolate, but not so good with bridges. They are just too soft.  

TIP: Open your bag of marshmallows the day before you plan to use them. They will harden overnight and be just right for making something.

My original thinking about this bridge made with toothpicks was that the students could not make a support leg underneath the bridge. My thinking was that the students would have to work hard to make the bridge work and I wanted them to concentrate on creating the bridge- not spending time making legs.  

This turned out to be futile! They wanted to make those support legs under the bridge to help hold it up! Of course, they did!  

TIP: If you try this bridge, be sure you allow an exploring time with the students. I found it very helpful to have each group try joining the marshmallows with toothpicks just as an experiment. After a few minutes, I had each group share a method they found that worked well. Check the photo of the bridge above. Can you see that the team doubled the number of toothpicks that joined each set of marshmallows? Clever! 

The Plastic Span

Building a Bridge in STEM Class- This fabulous STEM activity is to build a bridge using marshmallows. The bridge must hold weight and be a specific length.
Building a Bridge in STEM Class- This fabulous STEM activity is to build a bridge using marshmallows. The bridge must hold weight and be a specific length.

A year went by and we decided to try this bridge again. Instead of using tissue boxes, I decided to try a plastic box.  I have a large amount of these plastic shoeboxes and I thought it would be perfect. If we built the bridge going from one side to the other of the bin it would be a good length and the stiff sides would help hold the bridge in position.      

This time I allowed students to make support columns for their bridges. Some built the legs and some did not. In the photo on the right, the team added their little columns when the bridge started to sag a little. Fabulous improvement!  

TIP: Toothpicks can be very sharp! Caution students about this as they begin to work. I do use round toothpicks because they are more sturdy than flat ones.

Blueprints

Building a Bridge in STEM Class- This fabulous STEM activity is to build a bridge using marshmallows. The bridge must hold weight and be a specific length.
Building a Bridge in STEM Class- This fabulous STEM activity is to build a bridge using marshmallows. The bridge must hold weight and be a specific length.

This method developed after we tried using plastic bins. The first class tried the plastic bins and just built their bridges. I decided to try something new in the next class.

What if they had to create a blueprint of the bridge and then build it exactly like the blueprint?

You have to try this in your STEM class! Just hand out some graph paper and watch.

TIP: Using a blueprint introduces something unique to a STEM Challenge. Students can make small adjustments but not toss out their ideas and start over. When students are not happy about this I tell them about home builders using a blueprint for a house. What if the builder completely changed something about the house being built? Would I like that? No! I want the house built exactly like the blueprint. (We don’t use blueprints very often!)    

I had teams plan together for the bridge’s design and one student sketched the final plan. Then they set out to build it just like their sketch. Check the one on the left above. That’s pretty good, you have to admit. The team in the photo on the right had a very detailed structure and you can see just how fragile their bridge was when they tried to move it!

What fun! This is a STEM project that is quite challenging. My Marshmallow Bridge resource has all the details and includes the blueprint version, too! 

Click on any of the images to see this resource. You might also enjoy these blog posts:

Building a Bridge in STEM Class- This fabulous STEM activity is to build a bridge using marshmallows. The bridge must hold weight and be a specific length. Blog post with tips about using marshmallows.

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