In this interactive activity from the Building Big Web site, investigate dams in distress and decide if they should be repaired, removed, or left alone.

This activity is an entire-class lab experiment that refreshes the concepts of sinking and floating, while introducing the concepts of bouyancy and density using the fizz from sprite (carbon dioxide gas) and raisins.

In this video segment adapted from NOVA, scientists search for carbonized remains of plants preserved in lava flows to find out how long it has taken rain forests on Hawaii to regenerate after a volcanic eruption.

In this video segment adapted from ZOOM, cast members use a hair dryer to balance a ball in a stream of air, seemingly defying gravity.

In this video segment, the ZOOM cast is challenged to keep a ping pong ball in a funnel while the funnel is held upside down, seemingly defying gravity.

In this first part of a two-part lab activity, students use triple balance beams and graduated cylinders to take measurements and calculate the densities of several common, irregularly shaped objects with the purpose to resolve confusion about mass and density. After this activity, conduct the associated Density Column Lab - Part 2 activity before presenting the associated Density & Miscibility lesson for discussion about concepts that explain what students have observed.

Concluding a two-part lab activity, students use triple balance beams and graduated cylinders to take measurements and calculate densities of several household liquids and compare them to the densities of irregularly shaped objects (as determined in Part 1). Then they create density columns with the three liquids and four solid items to test their calculations and predictions of the different densities. Once their density columns are complete, students determine the effect of adding detergent to the columns. After this activity, present the associated Density & Miscibility lesson for a discussion about why the column layers do not mix.

In this lab activity, students determine density differences of water samples with varying temperature and salinity levels. Students synthesize information to predict the effects of oil in given water samples.

A lab where the students study the density of pennies. They will discover the limitations of measurements and the value of multiple trials.

Students explore the densities and viscosities of fluids as they create a colorful 'rainbow' using household liquids. While letting the fluids in the rainbow settle, students conduct 'The Great Viscosity Race,' another short experiment that illustrates the difference between viscosity and density. Later, students record the density rainbow with sketches and/or photography.

Why does an egg float in salt water? Learn about density and buoyancy in this video segment adapted from ZOOM.

Watch warm water float on top of cold water in this video segment adapted from ZOOM.

This video segment adapted from ZOOM offers a clever demonstration of buoyancy by showing how to pour a cup of air into a cup filled with water.

Will a grape float in oil? Will a metal nut sink in corn syrup? Watch as the ZOOM cast tests the buoyancy of a variety of liquids and objects.

In episode seven of the Beyond Penguins and Polar Bears podcast series, learn how scientists can get a first-hand look at changing polar icebergs and glaciers and what these changes can teach us about density.

This activity is a classroom experiment where students make observations, state hypothesis and carry out an investigation to draw conclusions.

This activity is a demonstration proving that carbon dioxide is more dense than air which leads to a deeper understanding of the term density.

Students will design, build and test a hot air balloon of their choosing. Students will construct and test components in order find three component optimum design features for final assembly.

In this video segment adapted from Design Squadí_í_íŹa PBS TV series featuring high school contestants tackling engineering challengesí_í_íŹlearn about the fundamentals of sound as student teams create percussive and stringed instruments for a local band.

In this video segment adapted from Design Squadí_í_íŹa PBS TV series featuring high school contestants tackling engineering challengesí_í_íŹstudents employ the concepts of tension and compression to build a suspension bridge without the aid of power tools.