In their lower school science class with Mr. Henry Sadler, the 7th-grade students worked with partners to model one of three volcano types: the shield, cinder cone, or composite.
Since 7th grade focuses on Earth and Space science, the class had a large unit on tectonic activity and volcanoes. They were required to decide on a type of model to create, and they had the freedom to design the type of reaction used to make the volcano explode.
There were several types of chemical reactions that the students used.
Vinegar + Bicarbonate Soda —> Carbonic Acid + Sodium Acetate
The carbonic acid is unstable, so it breaks down into water and carbon dioxide, causing the massive ‘eruption’ seen in the experiment.
hydrogen peroxide –› water + oxygen
Hydrogen peroxide is a molecule made up of hydrogen atoms and oxygen atoms. It can be expressed using the chemical formula, 2H2O2. Under the right conditions, hydrogen peroxide will undergo a chemical reaction to break down into two parts, oxygen and water.
Mentos and Diet Coke:
Carbon dioxide in soda is compressed into the liquid but it is under tension. The CO2 is attracted to any bumps that it can grab onto, which are called nucleation sites: places the gas can grab onto and start forming bubbles.
The surface of a Mentos is sprayed with over 40 microscopic layers of liquid sugar, giving it lots of nucleation sites. This means that every Mentos has the capability to have an incredible number of bubbles form on it when placed in soda. The Mentos sink, react with all the soda, and create massive foam.
A few creative students used a physical propulsion system rather than a chemical one. They essentially made a sort of Volcano shaped potato cannon, using pressurized air to propel projectiles (representing tephra, and volcanic ejecta) such as baking soda, rice, confetti, and foam blocks to display the eruption.