Saturday, February 25, 2012

Red Cabbage Juice - An Experiment Part 1

A few weeks ago, Danielle (SC's mom) told me about an experiment that can be done with red cabbage juice. I perused the internet for more information and found out that red cabbage juice is a pH indicator and one can actually create pH strips using red cabbage juice! The red cabbage juice will change colors depending on how acidic a substance is that is added to it. So, I bought a head of red cabbage and one Monday we began the process of creating cabbage juice for our experiment.

We first needed to boil the cabbage in water to extract the color from the cabbage.

We boiled the cabbage for about an hour to extract as much of the color from the cabbage as possible. We then let it cool and drained the cabbage.

I chose substances that had varying levels of acidity and a couple I was unsure about:
Baking Soda
Cream of Tarter
Lemon Juice
 I put each substance in a separate glass jar and placed them on a canvas. Everyone sat around the canvas as we began talking about red cabbage juice and it's magical and scientific properties.

We talked about the pH scale and about acids and bases. I showed them the red cabbage indicator color chart, which shows what color the red cabbage juice will change depending on the acidity of the substance added to it. We talked about how we can determine the acidity of a substance based off of this chart.

As we began our experiment, the preschoolers guessed whether each substance was a base or an acid and what color the cabbage juice would change to. This is what happened next:

I placed even amounts of cabbage juice and one substance in each jar, and we watched to see what happened. 

We noticed that when the vinegar was mixed with the cabbage juice, the mixture turned red. The lemon juice and cabbage juice mixture was almost pink. We talked about whether these substances were acidic or basic based on the color they turned in the cabbage juice and the preschoolers shouted, "Acidic!"

We noticed that the cabbage juice turned blue when mixed with baking soda. We again looked at our pH chart to find out whether the baking soda is acidic or basic and the preschoolers exclaimed, "Basic!"

The table salt did not change the color of the cabbage juice, so we discovered that it is a neutral substance. Finally, we mixed the cream of tartar in with the cabbage juice and the mixture became slightly lighter purple. It was hard to tell whether it was a neutral solution or an acidic solution, but we finally agreed on slightly "Acidic."

 Each jar of cabbage juice and the various substances were passed around the circle so the preschoolers could take a closer look at the color of each mixture.

Once we were done looking at each individual substance mixed with the cabbage juice, the preschoolers were curious to see what would happen when the substances were mixed together. I began by mixing the lemon juice mixture with the baking soda mixture and it began to fizz, bubble, and rise up and over the top of the jar. 

 The preschoolers laughed and screamed as the bubbles kept rising. We talked about the chemical reaction that was taking place with the acidic substance mixing with the basic substance. I continued to add our other mixtures in, one at a time to see what substances caused the most extreme reaction. The preschoolers watched intensely, hoping for more bubbles to rise up over the top of the jar. When we finished mixing all of the substances together, the preschoolers wanted to try even more substances... So, we began brainstorming what else we could add to our remaining red cabbage juice the following day. 

The next morning we talked about what substances we wanted to mix with the cabbage juice and IO quickly exclaimed "Tooth paste!" To find out what other substances the preschoolers chose and how our second round of red cabbage juice mixtures turned out, stay tuned for a follow-up blog!

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