Rock Cycle - Chemistry (1)
 Lab 

   
OBJECTIVES:
  • Exploring how states of matter can change.
  • Experimenting with a chemical change.
VOCABULARY:
  • chemical change
  • gas
  • liquid
  • matter
  • solid
MATERIALS:
  • baking soda
  • vinegar
  • red food color
  • clay

Students create a chemical change using vinegar and baking soda.


Lava is a liquid, that cools into rock, which is a solid. 
BACKGROUND:

Lava is molten rock (a liquid) that flows on the earth’s surface. Lava is formed inside the crust of the Earth by extreme heat; it erupts to form a volcano. During an eruption, many changes occur to the lava. First, as it cools, the lava changes state, from liquid to solid. Another change is the escape of gasses such as carbon dioxide, hydrogen sulfide, and water vapor, from the lava into the atmosphere.

In this lab, the students will model a volcanic eruption in order to simulate the chemical changes that occur in an erupting volcano. The children will see a solid (baking soda) and liquid (vinegar) mixing to form a gas (carbon dioxide) and a liquid.

STATES OF MATTER IN AN ERUPTING VOLCANO

LIQUIDS

SOLIDS

GASES

lava

rocks

carbon dioxide, hydrogen sulfide, steam
PROCEDURE:
  1. Before lab, assemble the vinegar, baking soda, clay, and red food coloring. If you do not have clay available, you can conduct the experiment in a plastic cup, flask, or test tube. If you are unfamiliar with the vinegar-baking soda reaction, you may wish to try it a few times, until you get a feel for the quantities of reactants necessary. Shape the clay into a "volcano" as a model for your students. Make sure you leave room at the top to place about a spoonful of baking soda.
      
  2. The students should be familiar with images of erupting volcanoes. You may want to show students pictures from the unit on Volcanoes from the Plate Tectonic Cycle.
      
  3. Explain to the students that during the eruption of a volcano, all the states of matter are present. Rocks are solids. Liquid is represented by the lava. Many gasses are emitted by the lava during an eruption. Plasma may even be present, in the form of electrical discharges in the sky above the erupting volcano.
      
  4. Tell the students that today they will make a play volcano and observe three states of matter: solid, liquid, and gas.
      
  5. Instruct the students to build a small volcano with clay, leaving a small crater-like opening on the top. The students will be able to clean the clay volcano, so the clay can be reused.
      
  6. Students should first place about 2-5 ml teaspoons of baking soda in the crater at the top of the volcano. Next, mix 100 ml of vinegar with a few drops of red food coloring (to make it look like a real volcano). Ask the students to pour the vinegar slowly on the baking soda. The resulting mixture will fizz as the vinegar reacts with the baking soda. Make sure they realize that the fizz is the release of a gas (carbon dioxide).
      
  7. Discuss with the students that what they have demonstrated is a chemical change. When vinegar (a liquid) is poured on baking soda (a solid), it produces a change to carbon dioxide (a gas).
      
  8. Explain that the gas escapes into the atmosphere, but some liquid and solid remain in the "volcano".

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