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Activity

Elephant's toothpaste

Summary: 
Make a foam as hydrogen peroxide rapidly splits into oxygen and water.
Science content (2016 curriculum): 
Chemistry: States of Matter, Properties of Materials (K-7)
Chemistry: Atoms, Molecules (3-7)
Chemistry: Physical Changes, Solutions, Mixtures and Separating (2, 4, 5, 6)
Chemistry: Chemical Changes (2, 7)
Lessons activity is in: 
Materials: 
  • hydrogen peroxide, either bottles available in a drug store (3%), or as oxygen bleach (cheaper)
  • dish soap
  • dried yeast
  • empty water bottle
    Procedure: 

    Add about a cup of hydrogen peroxide to the empty water bottle.
    Add a squirt of dish soap.
    Add a tablespoon of dried yeast.
    Swirl to shake, then set the bottle upright on the ground outside, or on on a tray if indoors (it will be messy).

    The hydrogen peroxide is split into oxygen and water, catalysed by the yeast: 2H2O2 -> O2 + 2H2O. The oxygen gas makes tiny bubbles. Molecule models can be used to show this chemical reaction.
    The dish soap stabilizes the bubbles to make a foam - one end of the detergent molecule does not like water ("hydrophobic") so it inserts into the gas bubbles; the other end likes water ("hydrophilic") so sticks outside the bubbles into the surrounding water. The soap molecules surround the oxygen gas bubbles in this way and stablize them so that they last for a longer time - as a "foam".
    As the oxygen is continually made the foam squeezes out of the bottle like toothpaste, for an elephant!

    Foam is a kind of a mixture called a colloid - gas bubbles in a liquid.
    See attached file for other colloids.

    http://www.imaginationstationtoledo.org/content/2010/08/dinosaur-toothpa...

    Attached documents: 
    Grades taught: 
    Gr K
    Gr 1
    Gr 3
    Gr 4
    Gr 5
    Teacher: 
    Ingrid
    Teaching site: 
    General Gordon Elementary Science Club
    ingridscience afterschool
    Activity originally developed and delivered: 

    Gordon Elementary Science Club