A second jar contains sand with alcohol. Because alcohol has a much smaller surface tension than water, the alcohol will flow into the small cracks between sand grains, filling the space. When the alcohol bottle is squeezed, the volume is already filled with sand and liquid, so the alcohol level in the tube must rise.

This demonstration has the potential to be dangerous if misused, and must only be used after instruction by Lecture-Demonstration personnel. The purpose of this demonstration is to illustrate the effect of vocal formants, not as entertainment for groups where the physics content is not discussed. Take a couple of big breaths of air first to get plenty of oxygen, then breath out completely before inhaling the helium. Videos of this effect may be more useful in many classes.

A marshmallow is placed in a bell jar. As the air is pumped out of the jar the pressure inside becomes smaller and the little bubbles of air in the marshmallow increase in size, inflating the marshmallow. Eventually much of the air originally in the marshmallow is pumped away. When the air is let back in, atmospheric pressure compresses the marshmallow to a small fraction of its original size.

An alternative demonstration uses a balloon with a small amount of air in it in place of the marshmallow. The photographs above show the marshmallow: before pumping, after pumping, and after the air is let back into the bell jar, and the balloon: before pumping and after pumping.

Please bring own marshmallow.