Comparing Density Lesson Plan (TEKS 6.6D): A Complete 5E Lesson for Mass, Volume, and Sink-or-Float

Chris Kesler · 10 min read

The first year I taught density, I wrote D = m/V on the board, gave a worksheet of word problems, and quizzed on Friday. Kids could plug numbers into the formula and still tell me with a straight face that a bowling ball sinks because it's heavy and a beach ball floats because it's light. The math was right. The thinking was wrong.

The moment that finally sold them was the can test. I'd drop a can of regular Coke and a can of Diet Coke into a clear tub of water at the same time. The regular Coke sinks. The Diet Coke floats. Same can. Same amount of liquid. Different result. The only difference is that one has sugar dissolved in it and one uses a tiny bit of artificial sweetener. The room would go silent for a second, and then the questions started. That demo was worth more than any worksheet I ever assigned.

That's the spine of this 5E lesson for TEKS 6.6D. The standard isn't asking kids to memorize a formula. It's asking them to calculate density to identify an unknown substance and predict whether an object will sink or float in a given liquid. You can't get there with a definition. They have to measure, calculate, and predict with their own hands.

⏱ 10 class periods 📓 6th Grade Chemistry 🧪 TEKS 6.6D 🎯 Differentiated for D + M 💻 Print or Digital

Inside the Comparing Density 5E Lesson

The 5E instructional model walks students through five phases: Engage, Explore, Explain, Elaborate, and Evaluate. It flips the traditional lecture-first sequence on its head. Students explore a concept hands-on before you ever explain it, which means by the time you do explain it, they have something to hook the vocabulary onto.

I switched to the 5E model years ago and stopped going back. Kids retain more, ask better questions, and stop staring at me waiting to be told the answer. The Comparing Density 5E Lesson is built on this framework from start to finish. Here's how it plays out across the five phases.

🎯 Engage

📷 Engage image — objective slide OR word wall card

Day one is a teacher-led can test demo with a student prediction sheet. Each student writes a prediction before the demo (regular Coke sink or float? Diet Coke sink or float?), records what actually happens, and then sketches what they think is going on inside each can at the particle level. The goal isn't a vocabulary lesson. It's a contradiction kids can't ignore.

By the end of the period, kids have committed to a prediction on paper, watched it fail or succeed, and started asking the right question on their own: "If they're the same size, why don't they do the same thing?" That question is the doorway into density.

What's included in the Engage:

Teacher directions for the can test demo (plus alternate demos if you can't get the cans)
Printable student prediction and observation sheet
Answer key for the discussion questions
Four learning objective slides (standard verbatim, "Calculate density" highlighted, "I CAN...", and "WE WILL...")
An illustrated Chemistry Word Wall in English and Spanish covering the full unit vocabulary

🔬 Explore

📷 Explore image 1 — wide shot of Station Lab in action

The Comparing Density Station Lab is the heart of the Explore phase. Students rotate through 8 stations (plus a 9th challenge station for early finishers) over one class period. The Station Lab is split into four input stations (where kids take in new information) and four output stations (where they show what they learned).

The four input stations:

🎬 Watch It! — Students watch a short video that walks through density, the formula D = m/V, and sink-or-float predictions, then answer guided questions.
📖 Read It! — A one-page reading passage at two differentiated reading levels, with a Spanish version included.
🔬 Explore It! — The hands-on heart of the lab. Students measure the mass and volume of three different small objects (a metal bolt, a wooden block, a piece of cork or wax), calculate density, and predict sink or float in water before testing.
💻 Research It! — Reference cards with the density formula, common density values for water, oil, alcohol, and various solids, and a sample identification chart for unknown substances.

The four output stations:

📋 Organize It! — A card sort where students place objects in order from least to most dense and predict which will float in water (density = 1 g/mL).
🎨 Illustrate It! — Students draw a layered density column with three liquids and three objects, labeled with density values.
✍️ Write It! — Three open-ended questions in complete sentences (this is where you find out who actually gets it).
📝 Assess It! — A short formative check with multiple choice density calculations and a fill-in-the-blank vocabulary paragraph.

📷 Explore image 2 — close-up of featured station (Explore It! or Organize It!)

Print and digital versions are both included. If you want the full breakdown of what happens at every single station, what students produce, and how to set it up, that's in our dedicated Station Lab post.

→ Read the full Comparing Density Station Lab walkthrough 8 stations, materials list, teacher tips

The Station Lab is included in the full 5E lesson. You don't need to buy it separately if you're getting the whole unit.

📚 Explain

📷 Explain image 1 — Presentation slide screenshot

Here's the payoff of doing the Engage and Explore before the Explain: by the time kids hit this phase, they've already measured, calculated, and predicted with their own hands. They have a working framework before you ever start naming things. The discussions get sharper, the questions get better, and you spend less time defining and more time pushing their thinking.

The Comparing Density Presentation walks 6th graders through the full scope of TEKS 6.6D, one concept at a time. The deck opens with a quick reset on the idea that density is how much mass is packed into a given volume, builds out the formula D = m/V with grams per milliliter (g/mL) and grams per cubic centimeter (g/cm³) as the common units, and then digs into how to measure each piece of the formula.

📷 Explain image (middle) — Presentation slide screenshot (classification hierarchy, Essential Question, or category comparison)

Students learn that mass is measured on a balance in grams and that volume can be measured two different ways. For a regular solid (a cube or a rectangular block) you measure length × width × height in centimeters and the answer comes out in cubic centimeters. For an irregular solid (a small rock, a metal bolt) you use water displacement: drop the object into a graduated cylinder of water, read the new volume, and subtract the starting volume to get the volume of the object in milliliters. The deck includes worked examples and a Quick Action INB where students practice calculating density step-by-step.

From there the lesson digs into the central comparison: water has a density of about 1 g/mL, and that becomes the reference point for almost every sink-or-float question students will see in 6th grade. If an object's density is greater than 1 g/mL, it sinks in water. If its density is less than 1 g/mL, it floats. The same rule applies in any liquid. An object floats in a liquid when the object is less dense than that liquid. The deck pushes against "heavy things sink and light things float" with the cargo-ship example: a 200,000-ton ship floats because its overall density (steel hull plus the air inside it) is less than the density of water, while a small steel bolt sinks because its density is much higher than water's.

📷 Explain image 2 — Presentation slide screenshot

The Presentation closes by treating density as a detective tool. Because density is a property of a substance, students can measure the mass and volume of an unknown sample, calculate its density, and then compare the result to a chart of known substances to identify what it is. The deck walks through a mystery-sample example where students calculate the density of an unknown chunk of metal and match it to aluminum, iron, or copper on a reference chart. That's the "identify an unknown substance" half of the TEKS standard, spelled out in a way kids can actually do.

What makes this deck different from a typical chemistry slideshow is that kids are doing something on almost every slide. "Your answer:" prompts appear regularly, Brain Breaks reset attention, Quick Action INB tasks (density calculations, sink-or-float predictions, an unknown-sample ID activity) keep students engaged, and Think About It prompts push deeper into bigger ideas like why ice floats on water (the only common solid that's less dense than its own liquid). The deck closes with a Check for Understanding tied back to the Essential Question: How can we use density to identify a substance or predict whether it will sink or float?

The Explain materials in this product include:

An editable 32-slide Presentation at two differentiated levels (Dependent and Modified), works in PowerPoint or Google Slides
A guided fill-in-the-blank student notes handout that mirrors the Presentation, with answer key
A Paper Interactive Notebook (English and Spanish) students cut, fold, and glue into their notebooks
A Digital Interactive Notebook at both levels with answer keys, for 1:1 classrooms or Google Classroom

The Explain runs across two class periods. The Think About It prompts are where the real discussion happens, so let those breathe.

🛠️ Elaborate

📷 Elaborate image — Student Choice Project board or sample student work

The Elaborate phase is where students take what they learned about density and apply it to a project of their own choosing. In this 6th grade chemistry lesson, that's a Student Choice Project board with six different project options plus a "design your own" pathway.

Students might build a layered density column with cooking oil, water, and corn syrup and predict where each of four objects will settle, design a children's book that explains why cargo ships float even though they're made of steel, or film a short demo where they identify an unknown sample by calculating its density. There are options for kids who love to write, kids who love to draw, kids who love to build, and kids who love to perform. Whatever the project, the point is the same: students apply density and sink-or-float reasoning to a real-world artifact instead of a worksheet.

Choice is the whole point. By letting students pick how they show their thinking, you get more authentic work for TEKS 6.6D and you actually get to see what they understand about the relationship between mass, volume, and density.

The rubric (the part teachers actually want)

Every project, no matter which option a student picks, is graded on the same rubric. Five categories at 20 points each: Vocabulary, Concepts, Presentation, Clarity, and Accuracy. The rubric uses a minus / check / plus shorthand on every row so you can grade a stack of projects quickly without re-reading every criterion.

Two differentiated versions in one file

The standard version is for students ready for independent application. The Reinforcement version is for students who need additional vocabulary or concept support. Three of the six options are swapped for projects with a tighter calculation tie-in, and "design your own" is replaced with "collaborate with the teacher" so kids aren't pitching cold.

✅ Evaluate

The Evaluate phase wraps the unit with a formal assessment. It's not all bubble-in. Several questions hand students mass and volume data and ask them to calculate density, identify the unknown substance from a chart, or predict whether the object will float in a given liquid.

The full assessment has 12 questions across five formats:

Multiple choice (4 questions) covering the density formula, units, and basic sink-or-float predictions
Hotspot / visual (2 questions) where students circle which object will float on a labeled density column or identify which has the highest density from a set of images
Multiselect (2 questions) where students pick all of the substances from a chart that will float in a given liquid
Short answer (2 questions) on why a giant cargo ship can float and a small steel bolt can sink
Multipart scenario (2 questions) where students calculate the density of an unknown sample, identify it from a reference chart, and predict whether it will sink or float in water

A modified version is included for students who need additional support, with fewer multiple-choice distractors and sentence-starter scaffolds on the short-answer items.

If you've taught all five phases, this assessment shouldn't surprise anyone. It's a chance for kids to show you they get it.

How everything fits together

If you want the whole experience (Engage hook, the Station Lab as the Explore, the Explain day with Presentation and interactive notebook, the Student Choice Elaborate, and the Evaluate assessment all in one download), that's the Comparing Density Complete 5E Science Lesson.

If you only need the one-day hands-on activity, the Station Lab works as a standalone. Most teachers buy the full 5E because the Station Lab works harder when it's bookended by a strong Engage and a follow-up Explain. But both are honest options.

Two options

Comparing Density Complete 5E Lesson cover

Full 5E Lesson — ~10 class periods $13.20 Get the 5E Lesson

Just the Station Lab — 1–2 class periods $7.20 Get the Station Lab

What you need to teach Comparing Density (TEKS 6.6D)

Materials beyond what's in the download:

One regular Coke and one Diet Coke (in cans), plus a clear tub of water for the Engage demo (or use the alternate sink-or-float demo included with the product)
Triple-beam balances or digital scales for the Explore It! station and the Presentation activities
Graduated cylinders (50 mL or 100 mL) for measuring volume by water displacement
A small set of test objects: a metal bolt, a wooden block, a piece of cork or wax, a small rock, a marble (one set per group)
Pencils, calculators, colored pencils or markers, and printed student pages
A device with internet for the Watch It! station and the slide deck

Standard covered: Texas TEKS 6.6D — Calculate density to identify an unknown substance and predict whether an object will sink or float in a given liquid. See the full standard breakdown →

Grade level: 6th grade science

Time: About 10 class periods of 45 minutes each, done with fidelity. The product also ships with a compressed sample unit plan if you need to move faster.

Common misconceptions this lesson clears up

"Heavy things sink and light things float"
This is the most common student explanation. It misses the size piece entirely. A giant cargo ship weighs tens of thousands of tons and floats, while a small steel bolt weighs less than an ounce and sinks. What matters is the ratio of mass to volume, not mass alone. Density is the idea that ties both together.
"Bigger things are denser than smaller things"
Students often mix up density with size or mass. A 1-gallon jug of water and a 1-liter water bottle have the same density even though the jug is bigger and heavier. Density tells you how tightly the matter is packed. Cut a chunk of iron in half and each piece still has the same density as the whole original piece.
"Objects with holes always float because they're empty"
Students see a boat or a hollow rubber duck and say "it has air inside, that's why it floats." The real explanation is that the object plus the air inside it has an overall density less than water. A metal boat shaped like a solid brick would sink. Shape matters because it changes how much volume the object takes up.
"Whether something sinks depends on the water, not the object"
Students sometimes think that changing the amount of water will change whether an object sinks or floats. A penny sinks in a tiny cup of water and also sinks in a swimming pool. The amount of water doesn't matter. What matters is comparing the density of the object to the density of the liquid.

What's included in the Comparing Density 5E Lesson download

📷 Inside-the-product — add screenshot of Read It passage or sample answer sheet

When you buy the Comparing Density Complete 5E Lesson, you get a single download with the whole unit:

✅ Engage materials — teacher directions for the can test demo, student prediction sheet, answer key, four learning objective slides, illustrated Chemistry Word Wall (English + Spanish)
✅ The full Station Lab — 8 stations + 1 challenge, print and digital, two reading levels, Spanish Read It!
✅ Explain materials — editable 32-slide Presentation at two differentiated levels (with built-in Brain Breaks, Quick Action INB tasks, and Think About It prompts), guided fill-in-the-blank student notes handout with answer key, Paper Interactive Notebook (English + Spanish), Digital Interactive Notebook at two levels with answer keys
✅ Elaborate (Student Choice Projects) — 6 project options + design-your-own, plus a Reinforcement version with calculation-focused alternatives, 5-category rubric included
✅ Summative assessment — full 12-question version and modified version with sentence-starter scaffolds, both with answer keys
✅ Sample unit plan — day-by-day pacing guide

A couple of real-talk tips from running this lesson

1. Do the can test live on Day 1, even if it's the only demo you do all week.

Kids who only see the formula on the board don't get a contradiction they have to explain. Kids who watch the regular Coke sink and the Diet Coke float in the same tub of water do. That contradiction is the whole hook.

2. Pre-fill your graduated cylinders to 50 mL before the Station Lab.

If kids have to fill, measure, dump, and refill at every rotation, they'll spend half the period on logistics. Pre-fill the cylinders, mark the starting line, and let them focus on the math.

3. Save 10 minutes at the end of the Station Lab day for a class debrief.

Ask: "If I handed you a chunk of metal and a chart of known densities, how would you figure out what the metal is?" That question pulls the "identify an unknown" half of the standard back to the center.

Get the Comparing Density 5E Lesson

Buy the full Comparing Density 5E Lesson — $13.20

Or if you only need the one-day hands-on Station Lab:

Buy the Comparing Density Station Lab — $7.20

(The Station Lab is included in the full 5E Lesson)

Frequently asked questions

Does this cover all of TEKS 6.6D?

Yes. The full standard is addressed across all five phases, with both halves of the standard (calculate density to identify an unknown substance, and predict whether an object will sink or float in a given liquid) baked into the Explore, Explain, and Evaluate.

What do my students need to know before this lesson?

Basic measurement skills (using a balance for mass and a graduated cylinder for volume) and how to multiply and divide decimals. Most 6th graders carry both in from earlier units.

How long does it take to teach?

Done with fidelity, about 10 class periods of 45 minutes each: one day for the Engage can test, two days for the Station Lab, two days for the Presentation and Interactive Notebook, three days for the Student Choice Project, and one to two days for review and the assessment. The product also ships with a compressed sample unit plan if you need to move faster.

Do I need special supplies?

Triple-beam balances or digital scales, graduated cylinders, a clear tub for the can test, and a small set of test objects (bolt, wood block, cork, rock, marble). Most schools have all of this in the science storeroom.

Does this work for digital classrooms?

Yes. Every component has a digital version. The Station Lab is fully digital-ready (Google Slides), the Presentation works in Google Slides, and the Student Choice Projects can be submitted as videos, slide decks, or written work.

Is this 5E lesson aligned to NGSS too?

It supports MS-PS1-2 work on analyzing and interpreting data on physical properties of substances to determine what they are. Built TEKS-first, but the standards overlap heavily.