With this experiment we'll cause marshmallows to make funny faces and demonstrate
a scien-terrific principle called pressure.
- Draw a face on both ends of a large marshmallow (the flat end). Draw 'em to look
like Dad if possible - it'll make the experiment much more humorous.
- Drop the marshmallow into a glass bottle. You'll have to make sure and use a bottle
that has a opening slightly larger than the marshmallow.
- Take the straw and wrap the clay about 1 inch from the end in such a manner that
the clay forms a 'ring' around the straw. Place the short end of the straw into
the bottle. The clay should stop the straw from dropping all the way into the bottle.
Now press the clay around the mouth of the bottle so that the bottle is completely
sealed and no air can get in (or out).
- Stand in front of a mirror so you can see the face on the marshmallow. Suck air
out of the bottle. Make sure there are not leaks in the clay.
Yeah! Pretty funny huh? Now stop sucking on the straw. What happens to the marshmallow
then?
Although a marshmallow appears to be solid it is actually filled with many pockets.
These pockets are filled with air (much like a sponge). When you suck the air out
of the bottle you are decreasing the pressure inside the bottle, which
causes the spongy solid - the marshmallow - to expand. When you stop sucking on
the straw and remove the straw from your mouth the air rushes back into the bottle,
increasing the pressure and causing the marshmallow to return to its original size.
Parent's Note. Pressure is often defined as force per unit area.
In physics, the term is usually applied to fluids (gases or liquids). If a fluid
is exposed to suitable forces, pressure is produced in it. The greater the force,
the greater the pressure. Pressure is measured in pounds per square inch in the
inch-pound system customarily used in the United States. It is measured in kilograms
per square centimeter or pascals in the metric system.