Buoyancy, Density and Pressure: Middle School Science

Eighth grade students at Mount Madonna School (MMS) recently learned more about how boats float, how airplanes fly and how submarines and hydraulics work, by engaging in an experiential “density diver” activity.

“Students are studying buoyancy, density, pressure, as well as Archimedes’, Pascal’s and Bernoulli’s principles,” commented teacher Nicole Silva. “When MMS transitioned briefly to remote learning over the holidays, I created take home bags with lab supplies so students could continue to do hands-on science via Zoom.

For this activity, each student had a “density diver” made by Silva out of a cut pipette, a nut and a safety pin to keep the nut attached, allowing it to have just the right amount of buoyancy, and a 2 liter bottle filled with water. As students exerted pressure to their water-filled bottles, they caused the density diver to sink or float – or even become neutrally buoyant – depending on how much pressure they applied.

“Students are learning firsthand about Pascal’s principle,” explained Silva, “and how an increase in pressure on a closed system increases the pressure equally everywhere. As they squeeze the bottle and increase the force, that increase in pressure is transmitted equally throughout the bottle and the water rises inside the density diver, increasing its density, therefore it sinks. When they release the pressure and decrease force, the water level drops inside the density diver and its density decreases and it floats. They then compare this to how real world submarines work using these same mechanics.”

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Contact: Leigh Ann Clifton, director of marketing & communications,

Nestled among the redwoods on 375 acres, Mount Madonna School (MMS) is a diverse learning community dedicated to creative, intellectual, and ethical growth. MMS supports its students in becoming caring, self-aware, discerning and articulate individuals; and believe a fulfilling life includes personal accomplishments, meaningful relationships and service to society. The CAIS and WASC accredited program emphasizes academic excellence, creative self-expression and positive character development. Located on Summit Road between Gilroy and Watsonville. Founded in 1979.