Candy Bar Density Lab

The Candy Bar Density Lab is an effective process skills lab. In this hands-on lab, students get to work with measuring mass, finding volume, determining density, and the opportunity to think like a scientist! Students take all of the research and data to then create a hypothesis and conduct an experiment. That is science at its best for a middle schooler! If this lab interests you, check out our other Science Experiments, Labs, and STEM activities!

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Candy Bar Density Lab Variations

Peanut Lovers Version

I conducted this experiment for the first time years ago before peanut allergies were a thing. Back then I ran the experiment with my students using Snickers and 3 Musketeers. And to be honest, I still prefer to do the experiment with these two candy bars. For one, it is easier to sell the difference in density from the beginning with Snickers claiming in marketing ads that it “satisfies.” When comparing the inside of each candy bar, it is easier to show the difference between the candy bars with Snickers having more “stuff”… aka=matter… in it (peanuts, caramel, nugget).

Peanut Allergies Version

With all of this being said, peanut allergies are a thing now. Especially if you work in a school setting. So, I have created a second version for teachers who need to adjust the lab to work for students with peanut allergies. I have found that Milky Way is a good second choice and even though it doesn’t have as much “stuff,” it does have a greater density than 3 Musketeers and will sink in water.

How to teach using the Candy Bar Density Lab

Make Observations

Besides gathering our supply list, we start by recording general observations. Students are asked to open one of each candy bar and setting it on a paper plate, cut each candy bar in half. Once the bars are cut in half, students are asked to draw what they see and write down three phrases or words to describe what they observe. For example, we wrote air pockets and fluffy for 3 Musketeers. Sometimes I like to open the candy bars and break them by hand to show the gooey caramel. 🙂

Collect Data

Using a triple beam balance the students gather the mass measurements. We review how to calibrate the balance and the proper way to find mass. Remind the students to use g to represent grams in their answer. Next, we use a ruler to find the length, width, and height. From there, I guide the students to use their calculators to find the volume. LENGTH X WIDTH X HEIGHT= VOLUME. Once they have the volume, the students find the density of each candy bar. Use the following formula to find density. MASS / VOLUME = DENSITY. Make sure to put g/cm3 behind your answer.

Write Hypothesis

Make sure to read the facts mentioned on the lab sheet about the density of water and what buoyancy is. This is a great time to discuss why certain things float in water and why some things sink. Students will then look over the data to write a hypothesis about whether or not they think the candy bars will sink. Now, I must tell you that I guide my students to look at the density of each candy bar. If the density is less than 1.0 g/cm3 (the density of pure water), then it should float. When the density of an object is more than 1.0 g/cm3, the object will sink in water.

Conduct Experiment

Now, it is time to test your hypothesis. Truth is, my class this week collected their data incorrectly somewhere along the way. So, both candy bars ended up with densities greater than 1.0 g/cm3. I think we forgot to calibrate the triple beam balance when we calculated the mass for one of the candy bars. So, when the students were writing their hypotheses, I did tell them that one would float even though their data said that neither would.

*In the end, the 3 Musketeers will float while the Milky Way will sink. The Snickers also sinks in water.

Draw Conclusions

Students will draw conclusions by illustrating their findings and answering a few questions about their experiment. At the end of the lab sheet, students are asked to fill in the words, increase or decrease, to make correct statements about density. Here are the answers…

When you increase mass, density will __increase__.
When you increase volume, density will ___decrease___.
When you decrease volume, density will ___increase___.
When you decrease mass, density will _____decrease___.

We do this lab when we are studying the planets. So, you will find a trivia fact at the bottom regarding Earth and Saturn. Earth is the most dense planet there is. If you were to drop Earth in a bathtub of water, it would sink. Even though Saturn is much larger, its density is far less than Earth. Hence, Saturn would float in a bathtub of water. You can demonstrate this using a golf ball (Earth) and a dodge ball (Saturn).