Foam – a substance formed by trapping pockets of gas in a liquid or solid. A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the regions of gas.

• closed-cell foam – the gas forms discrete pockets, each completely surrounded by the solid material. A camping mat is an example of a closed-cell foam: the gas pockets are sealed from each other so the mat cannot soak up water.
• open-cell foam – the gas pockets connect with each other. A bath sponge is an example of an open-cell foam: water can easily flow through the entire structure, displacing the air.

Fine foam

• wave dampening – physics phenomenon, a team of fluid mechanics researchers at Princeton University’s Complex Fluids Lab investigates the anti-sloshing abilities of foam.

Polystyrene foam – Polystyrene foams are good thermal insulators and are therefore often used as building insulation materials, such as in insulating concrete forms and structural insulated panel building systems. They are also used for non-weight-bearing architectural structures (such as ornamental pillars). PS foams also exhibit good damping properties, therefore it is used widely in packaging.

• Extruded closed-cell polystyrene foam is sold under the trademark Styrofoam.

What’s the problem?
How Bubbles Catch Comets (podcast 2:00) – Scientists wanted to catch a bit of comet dust, which holds secrets about the formation of our solar system. Comets fly really fast (like 40 times a bullet). What was needed was a way to capture comet dust that would not hurt the dust. So, scientists use a special foam, called an aerogel, which is 99.8 percent air with the rest being glass.
That’s engineering

• aerogel – Aerogel is the lightest solid substance ever made by man. Imagine a bowl of gelatin that has had all the liquid removed and replaced by air. Rather than collapsing, however, it retains its structure and feels like Styrofoam. That’s what aerogel is like. Its translucent appearance has earned it the nickname “frozen smoke.”