Color Mixing Lab the Next Phase: Studying Acids and Bases

Color mixing has become our big project at school.  If you have been following these posts you know we first started with several weeks of simple color mixing using water and food coloring.  The children were fascinated with the mixing of different colors.  We then experimented with adding our colored water to snow.  

The last week and a half we have been watching as our colors fizzed with baking soda and vinegar, so what next?  Well, why not some more experiments.  I boiled some purple cabbage and ended up with 4 cups of dark purple liquid.  The next day at school I put the cabbage juice in one of their tray compartments, and lemon juice and baking soda water in two other compartments.  The invitation was put out for exploration, lets see what happened.    

This student is pointing out to his friend that when the baking soda was added to the "purple water" the mixture began to turn blue.

Here we see what happened when the lemon juice was added to the cabbage juice, it began to turn pink.

 

Here we see a young scientist turning a blue mixture back to it's original purple by reversing the results  first baking soda, and then lots of lemon juice to turn it back.

When the children began asking why the colors were changing, I explained to them that lemon juice is what we call an acid and baking soda is what we call a base, the cabbage juice is neutral.  I asked them which one turns the cabbage juice from purple to pink and light purple, most told me the lemon juice.  So we talked about acids must then make things lighter.  I asked which made it turn turquoise and dark blue, and they said the water...which was water with baking soda, and we said that bases turn the color darker.

 

Each time the color changed,they were in awe, it was like magic because both the baking soda water and lemon juice are fairly clear, so the fact that they were mixing the colors was really exciting.

Trying at small amounts of liquid  had quicker results  as the little researcher in the photo above found out.  Another student in the picture below noticed that when she added her baking soda water first, the color changed on top but not on the bottom.

We had all sorts of variations of the three colors and questions and theories.  It was a lot of fun, but also a great way to approach science and the art of color mixing in one.

I can't wait to see what will be next in this color mixing journey!