Comparing Density Activity: 8 Hands-On Stations for Teaching Density of Liquids and Solids (TEKS 6.6D)

A short YouTube video introduces mass, volume, and the density formula. Kids answer three questions: the difference between mass and matter, the formula for calculating density (D = m/V), and a counterintuitive comparison about volume of two wooden objects of different sizes. Visual learners hook in fast at this station because the video shows the math worked out and the units explained, which makes the formula stick before students see it on a worksheet.

A one-page passage called "How a Lava Lamp Works" explains density through a phenomenon kids actually find cool. The passage walks through the wax blobs (cool wax is denser than the oil so it sinks; the heat lamp warms the wax, the wax expands, becomes less dense, and floats up; cooler wax at the top contracts and sinks again). Vocabulary is bolded throughout (mass, volume, matter, density, buoyancy). Three multiple-choice questions follow, plus the vocab notes section. Comes in two reading levels (Dependent and Modified) plus a Spanish version.

This is the heart of the lab. Kids build a layered density column. They carefully pour 50 mL each of corn syrup (density 1.4 g/mL), water (1.0 g/mL), and vegetable oil (0.9 g/mL) into a clear cup or graduated cylinder, in that order. Then they drop in four solids one at a time: a small ball of aluminum foil, a cork, a coin, and a glass marble. Each one stops at a different layer based on its own density. Three conclusion questions force them to explain which solids are most dense, list the liquids from least to most dense based on what they see, and compare cork vs. water. The visual is unforgettable.

Students examine 8 reference cards: the density formula (D = m/V) with worked example (a bouncy ball with mass 19 g and volume 27 cm³ has density 0.7 g/cm³), units (1 g/cm³ = 1 g/mL), two example rocks with mass and volume given (45 g/15 cm³ vs. 20 g/15 cm³), the rule for comparing densities (denser sinks below, less dense floats above), and three reference tables: densities of common liquids (water 1.0, corn syrup 1.4, motor oil 0.9, etc.), solids (gold 19.3, cork 0.2, ice 0.92), and gases (air 0.001293, hydrogen 0.00009, oxygen 0.0014). Six questions force kids to calculate density from given mass and volume, predict sink-or-float, and explain why ice floats in water.

A two-column card sort. Kids sort 9 cards into SINK IN WATER and FLOAT ON WATER columns. Cards include the four solids and one liquid from the Explore It! station (corn syrup, coin, glass marble, cork, vegetable oil, aluminum foil) plus three rule cards (more dense vs. less dense, > 1 g/cm³ vs. < 1 g/cm³, > 1 g/mL vs. < 1 g/mL). Sorting forces kids to connect the experimental result with the actual density value and the qualitative rule. Easy to spot-check at a glance.

Students get a data chart with seven substances and their densities (pine wood 0.4 g/cm³, water 1.0 g/mL, olive oil 0.9 g/mL, gasoline 0.7 g/mL, gold 19.3 g/cm³, wax 0.8 g/cm³, corn syrup 1.4 g/mL) and have to draw what those substances would look like layered in a beaker. Kids have to figure out the order from least dense at top to most dense at bottom, label each layer, and decide where the solids (wood, gold, wax) sink to within the liquid stack. Even kids who say "I can't draw" surprise themselves here because the diagram is just rectangles in the right order.

Three open-ended questions: what would happen if you put oil, water, milk, and honey in a jar, shook it, and let it sit for a day; what happens to a flowing lava lamp when you turn it off and wait a few hours; and how you'd test whether a collection of small solid objects is more or less dense than water. Forces kids to apply density to brand-new scenarios. This is the writing practice middle schoolers need and rarely get in science class.

Eight multiple-choice and fill-in-the-paragraph questions tied to TEKS 6.6D vocabulary (mass, volume, matter, density, buoyancy). Includes what an object less dense than the surrounding liquid does, identifying the densest layer in a four-liquid stack diagram (honey, water, liquid soap, ethyl alcohol), and predicting sink vs. float for a solid with density 2.1 g/cm³ in water (1 g/mL). The fill-in paragraph weaves all five vocabulary words together. If you're grading the lab, this is the easiest station to grade.

Four optional extensions: a Sink or Float? investigation where kids predict and test five classroom objects in water, a 10-question density quiz they design for a classmate (with answer key), an acrostic poem using "DENSITY" with illustrations, or watching the classic Diet Coke vs. regular Coke video and explaining (using density) why one floats and the other sinks. Requires teacher approval before they start.