This interactive activity from ChemThink takes a closer look at a covalent bond--how it is formed and how the sharing of two electrons can keep atoms together.

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.

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.

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 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.

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 as they build a truss bridge without the aid of power tools.

In this video segment adapted from ZOOM, cast members design and build door alarms using a variety of materials, including aluminum foil, batteries, and buzzers.

In this video segment adapted from ZOOM, cast members discover that metal is a good conductor of electricity as they play the steadiness tester game.

In this video segment adapted from ZOOM, cast members make a bridge from a single piece of paper. Will it be strong enough to hold a hundred pennies?

In this video from NOVA scienceNOW, learn how scientists detect potential signs of life on distant planets.

Diffusion is the net movement of particles from areas of high concentration (number of particles per unit area) to low concentration. In this activity, students use a molecular dynamics model to view the behavior of diffusion in gases and liquids.

In this short lab, students observe the movement of an air bubble in a small level, attached to a toy truck, as it is moved from a stop, to a steady speed and back to a stop. This gives a visual to the concepts positive acceleration, zero acceleration and negative acceleration.

In this interactive activity from the Building Big Web site, think like an engineer and use your knowledge of dome design to match the right type of dome to the right location in a fictitious city.

In Oakland, California, girls that are interested in science can participate in TechBridge, a technology program just for girls. Check out TechBridge in action at Montera Middle School. Find out what these girls like about TechBridge, and watch them build mechanical kangaroos and ostriches! [1:05]

This video, adapted from NASA, presents rare experimental evidence from the Fermi Gamma-ray Space Telescope supporting Einstein's prediction that space-time is smooth.