Atmospheric Pressure

Did you know that air has weight? This illustrated essay from the NOVA Web site explores conditions that affect air density and atmospheric pressure.

Atom Builder

Build a carbon atom out of up quarks, down quarks, and electrons in this interactive activity from the NOVA Web site.

Atomic Structure of an Alloy

Learn about the atomic structure of bronze, a copper alloy, in this video excerpt from NOVA: "Hunting the Elements."

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Bend, Twist and Break: Beyond the Laboratory

Dr. Chris Muhlstein explains that when scientists study fracture surfaces from controlled experiments to understand the resulting shapes and features, they can use their understanding to deduce what happened when they were not around to see the material fail or break. Further they can predict what will have to a larger or smaller piece of material under stress. This process is how scientists and engineers translate a lab experiment into a design for an airplane, bridge or even a bike frame.

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Bend, Twist and Break: Breaking Glass

Dr. Chris Muhlstein explains that researchers learn about the scientific basis for failure of materials by running experiments in the lab, using a simple shape like a glass rod to calculate the strength of material and predict its failure. The same tests can be done at the micro and nano scale using tiny specimens. Students can run a similar experiment with a bar of chocolate.

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Bend, Twist and Break: Fracture Surfaces

Dr. Chris Muhlstein explains that fracture surfaces can reveal how and why a material has failed. An image of a fracture surface has features or shapes that we can use to understand where a material failed and why. Scientists use an optical microscope or a scanning electron microscope to read a fracture surface at high magnifications, much like we read maps to find our way.

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Bend, Twist and Break: The Bridge

Dr. Chris Muhlstein explains that the arrangement of atoms in a material determines the properties. He drops an iPod to illustrate how the arrangement of atoms can protect it from damage; he narrates footage of the collapse of the Tacoma Narrows Bridge in the 1940s to show how the deformation of materials can cause the collapse of a structure.

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Birth of a Supernova, Type Ia

In this interactive activity from NOVA Online, learn about a type of exploding star — a Type Ia supernova — that is so bright that astronomers can measure the distance to the galaxy in which it resides, and even learn which elements make up the star.

Birth of a Supernova, Type II

In this interactive activity from NOVA Online, learn about a type of exploding star — a Type II supernova — that is so large it has a mass 10 times greater than the mass of our Sun.

Breaking Things on Purpose

*Materials such as metals (aluminum, iron, copper, etc.), ceramics (silicon carbide, porcelain) or polymers (milk jugs made of polyethylene) are tested by scientists and engineers to reveal certain mechanical properties such as the maximum stress a material can withstand. The stress at which a material breaks is a measure of its strength. In this lesson you will be testing the strength of a delicious material you know as chocolate!

Build a Steroid

In this interactive activity from NOVA, learn about the molecular structure of steroids. See the intermediate molecules that are part of the pathway for synthesizing cortisone from diosgenin.

Building Blocks of Matter

Structure of matter.

Carbon Cycle Diagram

This diagram from NASA's Earth Science Enterprise illustrates Earth's carbon cycle.

Chernobyl: What Really Happened?

This text excerpted from Richard Rhodes' book, Nuclear Renewal and reprinted on the FRONTLINE Web site examines the causes of the Chernobyl accident.

The Dating Game: Radioactive Carbon

In this media-rich essay from the NOVA Web site, learn about the atomic structure of radioactive carbon and how it can be used to determine the age of organic remains, such as bones and teeth.

Design an Ion Engine

Learn about ions and then design an ion engine to maximize thrust in this interactive activity adapted from NASA.

Diamonds: The Science Behind the Sparkle

This illustrated essay from the NOVA Web site explains why the atomic structure of a diamond slows down light and produces a sparkle more brilliant than from any other colorless substance.

Disappearing Milk

A magician pours milk into a glass, but when he turns the glass upside down, nothing comes out. How does he do it? Discover the science behind the "magic" in this video adapted from the American Society of Mechanical Engineers.

Discovering Air

Our understanding about the air we breathe has changed dramatically through time. This illustrated timeline from the NOVA Web site tracks the changing thought on air and the creation of the Periodic Table of the Elements.

Dissolving Salts in Water

In this interactive activity adapted from Iowa State University, design and carry out an experiment: dissolve salts in water, see how different ionic compounds produce different reactions, and observe the resulting changes in temperature.