	All ages with adult supervision
	Mixing two reactive materials
	10 - 20 minutes
	Identification: Yellow/amber colored liquid with rubber-like odor. Mildly toxic by ingestion and inhalation. Irritating to body tissues and respiratory tracts. Avoid all body tissue contact. Do not breathe vapor. Identification: Dark brown liquid; odorless. Irritating to body tissues and respiratory tract. Avoid all body tissue contact. Do not breathe vapor. Combustible liquid.
	Understanding of changes caused by chemical reactions
	Golly! WOW! Gee whiz! rating - 8. This is a great Gee-Whiz demo for all grades and audiences.

Super Foam Demonstration

        Good question and answer preliminaries help set the stage (see the video), and showmanship is important. Best done with a member of the audience so that as foaming takes place, they can respond to questions, give comments and hopefully express surprise as the foam tries to leave the container.
We've been able to find the two components at the hobby shop. You can also order it from:

Flinn Scientific, Inc.
1-800-452-1261
P.O. Box 219
Batavia, IL 60510
Catalog No. C0335 - Polyurethane Foam System

Procedure

The process is very simple: mix approximately equal volumes of the two components together in a paper or plastic cup, stir and watch the foam form. Very effective if done in a clear plastic cup so the audience can see the process. Be sure to use enough so that the foam comes all the way out of the cup: this is the most effective and interesting part of the entire demonstration. To be safe, wait 24 hours before touching the foam

Keys to the overall effectiveness include:

Asking questions and getting comments from the students regarding what might happen when two reactive materials are mixed, and of what is happening; for example:

Reactions between liquids often generate other materials such as gases and solids.

During the mixing process, ask for comments on color changes, heat liberated (are you feeling anything through the cup?), changes in viscosity or thickness

As the foam begins to form, have the student leave the mixing tool (a wooden spatula or wooden dowel) in the foam as it rises. When he lets go (at your suggestion), it stays in place and the foam continues to move up and out of the container

    Other discussions before and after the demonstration might focus on changes in properties caused by reactions (color changes, gaseous by-products, solidification) compared to changes in phase (liquids going to solids, but with no chemical reaction; this is very different from what happens here). Questions and observations about the properties of the material that's generated could include:

Is this material flexible, light (low density)?

Does it smell? If you touch it, how does it feel?

Does it have good toughness, flexibility, impact resistance? (have the student pull on it, push on it and hit it with something)

    Discussion of applications of science to new technology (real world use of the results of science) could focus on how chemistry generates useful products such as polyurethane foam.   Applications of this foam include:

Model airplane wings and model train "mountains"

Insulation for homes, airplanes, refrigerated tankers, refrigerators, ice chests and coolers, trucks, and inside the walls of most buildings

In-place foamed packaging for protecting electronic devices and computers

Cushions for chairs, sofas and seats in cars, trucks, airplanes and the home

Run-flat tires in which the polyurethane foam on the inside of the tire provides support after the air has leaked out

    Finally, ask the audience if they know of any other applications of foam materials. They should come up with lots of others, most of which will not be of the same kind of foam (polyurethane) but of other kinds. The answers to this question should lead to discussion of polystyrene foam and "peanut" foam made out of starch. These are very different in both chemistry and how the foams are made.
    The polystyrene foam involves thermal release of a low boiling hydrocarbon (usually pentane) which is trapped in the solid polystyrene particles. This kind of heat-generated foaming also involves a phase change for the pentane liquid going to a gaseous state. Unlike the polyurethane foam, polystyrene foam easily dissolves in organic solvents such as acetone or toulene (nail polish remover); this makes an effective demonstration in conjunction with the polyurethane foam (see Shrinking Peanuts). Polyethylene foam is now being used in insulation as well, but is even more insoluble than the polyurethane foam: it doesn't dissolve or absorb much of anything, which makes it great for applications where water and solvents might be present.
    Further discussion of technology and applications of polyurethane foam may involve:

Use of the foam as an adhesive and support between two rigid materials; plywood with foam in the middle used in pre-fab wall sections for building houses

Use of spray-can polyurethane foam for insulating cracks and small holes in houses and for filling walls after construction is complete (this is dangerous because pressure can build up that blows the walls out)

Doing the foaming process in a sealed container: this must be done carefully. A Tupperware container works great because it is clear and the lid will pop off before dangerous pressure builds up.

    An activity for the student in which urethane foam is used to encase an egg (this must be done with supervision and perhaps with rubber gloves to ensure protection). Follow-on would be dropping the encased egg from the top of a building to see if it survives.

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