Everyone pretty much knows how to make a volcano using vinegar and baking soda. You make a mound with home made dough, Play Doh or some other modeling compound, put in some vinegar and then drop in the baking soda (or have the baking soda in the mound and pour in the vinegar). Most of the time I have added a bit of red food coloring to make it a bit more dramatic. What if you could change it up a bit? What if by making some red cabbage juice you could have a color changing volcano? If you did my "Acid or Base" experiment posted earlier, you know that red cabbage juice changes color depending on if it is mixed to an acid or a base. If you took my advice and saved the red cabbage juice then your are probably ready to go with this experiment.
What you will need:
Red Cabbage juice (How to make it)
Child's medicine syringe, eye dropper or pipette (plastic eye dropper)
White plate or light colored so you can see the color change better
To make your volcano mound you will need to:
In a cup, mix 4 Tablespoons baking soda, 1 tablespoon flour and 1 to 1 1/2 tablespoons red cabbage juice ( this is enough to make two small mounds). Stir together dry mix with 1 tablespoon red cabbage juice. Add 1 teaspoon red cabbage juice at a time as needed to make a crumbly paste. (If you add too little liquid your mound won't hold together as well, but if you add too much your mound won't hold it's shape.)
Take half of the mixture and put onto the plate. Mold it into a mountain shape in the center of your plate. I added a small indent in the center of the mountain. Mine is a rather large indent. Since you have enough mixture to make two, try making one with a very small indent and one with a larger indent just for fun.
Now you will need to gather:
A cup filled with red cabbage juice
A cup filled with white vinegar
Your medicine syringe or dropper
I suggest you take everything outside in case there are spills.
Now you are ready to begin.
1: Pour some of the red cabbage juice around your volcano. Your volcano is an island in the middle of the sea. Observe how the purple juice changes color around the volcano and slowly makes the whole sea blue.
2: Draw up some vinegar and drop it onto the volcano. You can keep doing this until your volcano has dissolved. To really see the color change effect squirt some vinegar on the side of your volcano. It will bubble less and you will be able to see the sea change color. You will need to pour off the old red cabbage juice at some point. Your volcano won't slide around on your plate so you can just dump the juice in the sink or in the dirt. Add more red cabbage juice around your volcano and keep going.
In this picture you can see the reaction of the vinegar added to the center of the volcano. You can also see what happened when I squirted the vinegar down the side of the volcano. You get a much clearer view of the color change when adding the vinegar down the side and it will make neat swirls.
What you are going to see:
The reaction between the vinegar and the baking soda will cause a bubbling action. Depending on how concentrated your cabbage juice was when you add it to the baking soda mount it will turn anything from a lighter blue-green to a deep blue. When the vinegar (acid) hits the baking soda volcano the initial color reaction is to turn red (if you look closely you can see the bubbles have a pink hue to them). When the "lava" hits the "sea" it will turn pink red-ish color. As it mixes together it will turn back into purple. The color changing you are looking for is in the volcano mixture when you mix it. Then when you pour your purple juice around the volcano, it will slowly turn blue. When your volcano erupts it will again change the color of the "sea".
How this works:
If we go back to the Acids and Base experiment, we learned how acids and bases effect red cabbage juice. Bases (like baking soda) turn the red cabbage juice blue. Depending on how basic the solution is the color change will be anything from green to deep blue. Acids (like vinegar) will turn the purple cabbage juice anything from light purple to a red-ish pink depending on how acidic they are.
The bubbles created when mixing vinegar and baking soda are evidence of carbon dioxide gas. The bubbles are filled with the colorless gas.
*My volcano was made using red cabbage juice that was not reduced. The stronger your red cabbage juice is the deeper blue your volcano will be. As you can see if you don't reduce it, both your indicator strips and your volcano will work just fine.
I hope you try this and I hope it makes you want to try the Acid or Base experiment too.
Stand by with the cabbage juice.............if you have any left. See what plans I have for it for Easter........