Rocket ScientistMarshmallow Mystery

 

StarWhat you need:

  • glass jar - the marshmallow should be slightly smaller than the mouth of the jar
  • marshmallow
  • straw
  • Playdoh™
  • mirror

StarWhat do you do?

  1. Drop the marshmallow into the jar.
  2. Wrap the clay around the straw about 1 inch from one end of the straw.
  3. Position the straw so that the small end is inside the jar.
  4. Hold onto the straw, then cover the mouth of the jar with Playdoh. (Make sure you have a tight seal.)
  5. Holding the jar, stand in front of a mirror so you can see yourself.
  6. Suck some air out of the jar. What happens?
  7. Stop sucking on the straw. What happens to the marshmallow now?
  8. Try blowing into the jar. What happens now?

StarHow does it work?

A marshmallow is a type of colloid. A colloid is when you evenly distribute bits of one substance through another.

Air is trapped in many spaces within gelatin, creating a marshmallow.

When the air is sucked out, the pressure within the jar decreases. The lower amount of pressure within the jar makes the marshmallow increase in size.Allowing air back into the jar increases the pressure within the jar, thus causing the marshmallow to return to its normal size.

Other examples of colloids are:

  • Gels -- liquid floating in a solid. Water droplets floating in protein creates gelatin.
  • Aerosols -- liquid floating in a gas. Water droplets floating in air create fog.
  • Foams -- gas floating in a liquid. Gas floating in cream creates whipped cream.
  • Emulsions -- liquid floating in another liquid. Oil floating in vinegar creates mayonnaise.