Let’s Discover: Density Cake

Cooking is fun! And, it can be very educational; after all, every element of cooking and baking is scientific. In this month’s edition of Let’s Discover, you and your child will get to spend some fun time in the kitchen learning all about density.

Density is basically how much “stuff” is smashed into a particular area…or a comparison between an object’s mass and volume. Remember the all-important equation:  Density = Mass divided by Volume

Based on this equation, if the weight (or mass) of something increases but the volume stays the same, the density has to go up. Likewise, if the mass decreases but the volume stays the same, the density has to go down. Lighter liquids (like water or rubbing alcohol) are less dense than heavy liquids (like honey or Karo syrup) and so float on top of the more dense layers.

The same amount of two different liquids will have different weights because they have different masses. The liquids that weigh more (have a higher density) will sink below the liquids that weigh less (have a lower density).

In this experiment, we will be baking a cake using ingredients that have different densities: marshmallows, chocolate cake mix and cherries. When the cake goes in the oven, watch the magic happen – the most dense layer will be placed on the top and the least dense layer will be placed on the bottom. As the cake cooks, the top and bottom layer will switch places as the less dense materials move to the top and the more dense materials sink to the bottom.

Materials:

• Cake mix (flavor is up to you, we used Devil’s Cake)
• Bag of mini marshmallows
• 2 cans of cherry pie mix with whole cherries
• Eggs
• Oil
• Water
• Clear glass cake pan

Procedure:

1. Prepare cake batter according to the box directions.
2. Spray the bottom of the cake pan with cooking spray.
3. Cover the bottom of the pan with marshmallows.
4. Pour cake batter over the marshmallows.
5. Layer the cherry pie filling 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. You have to check in on the baking process to watch the science. The baking is the best part (besides eating the cake of course!). As the marshmallows rise to the top, they will melt and become gooey (yum!).

HINT – during our experiment, the marshmallows completely melted and disappeared. You may want to try baking your cake more slowly at a lower temperature to preserve the marshmallows. As the cherries fall to the bottom, they will only be visible after cutting the cake or looking through the clear bottom.

Questions:

1. What other ingredients can you use to switch places in this yummy experiment?
2. Why do the layers switch places during baking?

 

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