Summary
Students will investigate the relationship between mass and volume, which leads to density. This lesson includes modifications for advanced classes if needed.
Essential Question(s)
How do you explain density?
Snapshot
Engage
Students predict whether objects will sink or float.
Explore
Students measure density cubes and analyze the data.
Explain
Students connect what they learned with the density cubes to analyze a density tower.
Extend
Students try to get a piece of modeling clay (such as Play-Doh) to float.
Evaluate
Students construct a tweet about what they learned.
Materials
A variety of objects of different densities (see Engage for ideas)
A clear plastic tub, filled with water
Sets of density cubes (Explore)
Explore handout (attached; one per student)
Inside Out handout (attached; one per student)
Explain Slides (attached)
Modeling clay, such as Play-Doh (Extend)
Engage
Students will walk in, and a variety of objects and a big tub of water will be placed at the front of the room. Either post directions or ask students to construct a three-column chart in their notes and title the chart, “Will It Sink or Float?” The first column is labeled “Object,” the second column is labeled “Prediction,” and the third column is labeled “Actual Result.”
Direct students to write each object displayed in the object column, and then have them predict whether they think the object will sink or float when put in the water. Allow students to hold the objects if they want. Once they’re done with their predictions, have students share their predictions before you put the object into the water. Then, put the objects into the water. Have students write down the actual results as they happen.
Explore
Offer a set of density cubes to each pair of students, along with rulers and mass scales around the room.
Allow students time to investigate the different blocks. Common observations usually include that all the blocks are the same size (which can be verified by the ruler), but they’re different colors and have different “heaviness.” Allow students access to the scales to investigate the idea of “heavy” and “light.” Also, give access to graduated cylinders and water for a further investigation of water, so students can relate each cube to the density of water. Either give each student a copy of the attached Explore handout, or post the questions on the handout for students to write in their notebooks.
Explain
Pass out a copy of the attached Inside Out handout to each student (or have them copy the Inside Out design into their notebooks). First, have students brainstorm what they know and have learned from the Explore in the middle circle (this should take anywhere from 2-5 minutes). Then, have students share what they’ve written with an elbow partner.
In the second circle, have students write what their partner has written that they forgot to include (this should also take 2-5 minutes). Next, show the YouTube video of making the density tower.
When the entire video has played, go back and pause it at 1:11, which is the full density tower. In the biggest circle, students should write what they’re seeing and why they think the layers are possible.
Finally, display the attached Explain Slides, asking questions about the layers. Have students work in their pairs to answer the questions in the biggest circle. Ask students to share their thoughts and answers, clarify misconceptions and explain that it’s possible to layer liquids because they have different densities. Also, discuss how objects will sink down to the layer that has the closest density to the object.
Extend
Going back to the tub of water, grab a piece of balled-up modeling clay and show it to students. Drop it in the water and comment on how it sank. Tell students they will receive their own piece of modeling clay, and their task will be to make it float. Pass out the attached Extend handout, where students will document their thought-process and the success/failure of their attempts (or you can post it and have students draw it out in their notebook).
Give students no more than 15 minutes to complete this task. If they don’t find success, then that’s fine; it’s just something to consider when they reflect on the task. However, when the struggle becomes real for students, you can give them hints like "How does the density of water compare to the density of the modeling clay right now?" then "If you have to use the entire mass of the clay I gave you, how can you make its density lower than water?"
Evaluate
Students will summarize all that they’ve learned about density in a Tweet Up. In 140 characters or less, have students write about what they’ve learned, and use whatever appropriate hashtags they think add to what they’ve written. When they've written their tweets, have students share out their responses. This is the opportunity to assess their learning in the moment and clear up misconceptions.
Resources
Inside Out (Explain): K20 Center. (n.d.). Inside out. K20 Learn. https://learn.k20center.ou.edu/strategy/a89b55a468ff764491d10ec5b2005c9d
Density Tower (Explain): Spangler, S. (2010, December 8). "Amazing 9 Layer Density Tower" Sick Science! [Video]. YouTube. https://www.youtube.com/watch?v=-CDkJuo_LYs
Tweet Up (Evaluate): K20 Center. (n.d.). Tweet up. K20 Learn. https://learn.k20center.ou.edu/strategy/d9908066f654727934df7bf4f505fb94
Density Cubes (Explore): Arbor Scientific. (n.d.). http://www.arborsci.com/set-of-density-blocks