Marshmallow and Cherry Density Layer Cake

By Susan Wells, Steve Spangler Science

This experiment mixes a little kitchen science, candy science and physical science. And the end result of this activity is delicious.

The cherries and marshmallows in this cake switch places, thanks to density.

To make a three-layer density cake, you will need the following materials:
  • Cake mix (flavor is up to you, we used Devil’s Cake)
  • Bag of small marshmallows
  • 2 cans of cherry pie mix with whole cherries
  • Eggs
  • Oil
  • Water
  • Clear glass cake pan
  1. Prepare cake batter per box directions.
  2. Spray the bottom of the cake pan.
  3. Cover the bottom of the pan with marshmallows.
  4. Pour cake batter over the marshmallows.
  5. Layer the cherry pie filing on top of the batter. Do this quickly, as the marshmallows will start to float up almost immediately.
  6. Bake the cake according to box directions.
As the cake bakes, the marshmallows and cherries will switch places. As the marshmallows rise to the top, they will melt and become gooey. As the cherries fall to the bottom, they will disappear, along with the pie filing.

How does this work?
The answer lies in density. Density is defined as mass divided by volume or the amount of stuff in a certain amount of space. Marshmallows are a mixture of sugar and gelatin, puffed up with air. They are much less dense than the cherries. The marshmallows are less dense than the cake batter too, so the marshmallows rise up through the batter. The cherries are more dense than the batter, so they fall to the bottom.

This experiment was developed by former teacher and Story Time Slime speaker Julie Gintzler as a 100-day activity with her class. She lined 100 marshmallows on the bottom of the cake pan as part of the celebration.

Susan Wells is a social media specialist and blogger for Steve Spangler Science. She is a mother of two girls who loves to find the learning in everything. Susan also runs the science fair and science clubs at her girls’ school. Follow Susan on Twitter and check out all of Steve Spangler’s educational boards on Pinterest and scientific posts on Facebook.

Can You Eat Giant Gummies? and a book giveaway!

After I wrote a guest blog post about giant gummies for Lisa Bergantz of, she decided to do it on TV. When she demonstrated the gummy experiment on Good Things Utah, she mentioned that she'd dared her kids to taste them, and they tasted awful, because the flavor is so diluted. (You can watch the clip here--the gummy section starts about 2 minutes from the end.)

I started thinking about that. She's certainly right, that the flavor is diluted by all the water the gummies have absorbed. But is there something else going on?

Here is my test gummy worm, which has absorbed so much water and grown so enormous that it no longer fit in the drinking glass, and broke in pieces:

Can you see the cloudy water at the bottom of the cup? Something's been dissolving, and it's probably not the gelatin (which has absorbed all the water that made the gummy grow, and is still holding the gummy together.) I stuck a straw in to find out. Sure enough, the water was sweet and a little candy flavored, kind of like a weak Koolaid. So, not only has the flavor of the gummy been diluted by all the extra water, it's also been diluted because some of the sugar and flavor has dissolved into the water.

(I definitely do not recommend eating the gummies, which are more like weak-flavored Jell-O, or drinking the water. This was done for the sake of science!)

Lisa is also holding a Candy Experiments book giveaway at her blog, Find out how to enter here!

Candy Experiments Blog Tour #5: Can You Sink a Marshmallow?

I'm finishing up this week's blog tour with a stop on Steve Spangler's blog. Steve Spangler is the author of several experiment books for children. He's also made multiple TV appearances, and he turned the Diet Coke/Mentos geyser experiment into an internet phenomenon. His website has science experiments for almost any topic.

Visit to read Density in Action: Can You Sink a Marshmallow?

And don't miss the blog's giant squid article!

Candy Experiments Blog Tour #4: The Colors In Your Candy

For this blog post, I separated colors for popular candies: brown M&M's, black jelly beans, purple Skittles, and even red CakeMate hearts (which, surprisingly, have more dyes than just red).

Read all about these candy colors at Biting the Hand That Feeds You.

Candy Experiments Blog Tour #3: The M&M Color Wheel

Mama Jenn homeschools five children, and posts great ideas for homeschool activities and crafts. After I saw her idea for a color wheel, I decided to try it with M&M's. Read about Color Wheel Candy Experiments at Mama Jenn's blog.

Candy Experiments Blog Tour #2: The Incredible Growing Gummy Worm

On day two of my blog tour, I stop by with instructions on how to turn a gummi worm into a huge gummi snake. (The key is gelatin.) Follow this link to read The Incredible Growing Gummi Worm.

Lisa, a blogger and mother, draws on her science background to create art and science activities for her kids. She first contacted me when she was planning to demonstrate candy experiments on a local TV show, and I've enjoyed checking back to see her science lessons. Thanks, Lisa!

Candy Experiments Blog Tour #1: How it All Happened

I'm launching my blog tour with an interview by Laurie Thompson, a friend who writes children's articles and has an upcoming picture book about a man who bicycled across Ghana with only one leg. On her blog she recommends children's books, posts author interviews, and blogs about her own writing experiences.

Find out how Candy Experiments got started, what the writing process was like, and what kind of weird questions I had to research, on Laurie's blog!