Purple, Green, Pink and Back

Apologia Biology Module 14 – Anthocyanins and pH levels determine leaf color.

When my son’s class did this experiment last year, they never to got to the point of it changing to pink.  They used tap water and I guess the pH levels in it were at such a level it took way to long to change it.  Whatever the reason, Sir Husband said we should use distilled water this year.  And that is just what we did.

We boiled the red purple cabbage in a little pot brought from home.  This burner is on loan from my MIL. I think I should just keep it.  I’ll hide it and maybe she won’t ask for it back.  One can hope…

Because we used Distilled water, our cabbage juice was a pretty shade of purple.

The students observed the color and noted it in their notebooks.  Afterwards they started adding drops of  a water/ammonia mixture.  This is a base and raised the pH levels to above nine, which makes the anthocyanins green.

By adding and acid (vinegar), the pH levels were lowered to below seven, the anthocyanins turn purple. Adding more vinegar brought the pH levels even lower down below four which made the athocyanins pink.

Really is a pink color.  The photo doesn’t show it well.

The best part of this kind of experiment is making it work backwards.  The students added more base to change it back to a blue or purple color.

This experiment shows that the pH levels of water can determine the color of leaves containing Anthocyanins. Pretty cool, huh?

When that was done, the students wanted to add more acid and change it back to pink.  See, how fun it is to have an experiment that works just as great backwards?   Below is a video.  You’ll have to tilt you head to the left to watch it.  Why? Because I am a complete idiot and turned my camera sideways to film this.  This is a trait I think I have passed down to at least one of my children. Lord, please help that child.

What I want you to see is the color change, but I want you to hear is the surprise from the students.  🙂

13 responses to “Purple, Green, Pink and Back

  1. 🙂
    We’ve done a similar experiment, where we had the cabbage juice in about 6 diff glasses, and added diff things to each. We determined whether the Ph was high or low….. or something like that. It was last year! ha.
    Never did one glass where we changed it’s color several times, tho.

    I like the video!
    I like Apologia! 😀

  2. I want to see the student with the really deep voice in the background. He/she sounds like the voice has been modified for the witness protection program.

  3. We really liked this experiment and changing the colors back and forth like you all did. =) I’ve made a video recording sideways before too. @@

    Speaking of voice, before John moved out when he was 18 the four of us ate out. When John placed his order to the waitress, she dropped her pad and pencil because of his voice. She asked him if he is in radio. I still chuckle over that.

  4. Kristy,

    OH! LOL That is the boy who wore the gas mask when we dissected the frog. He sounds normal to me. Actually this is a top secret science class and all innocent people have been changed to protect you from them. To be honest, we are not even there. This is all computer generated to confuse my blog readers. Yeah, that’s it. That sounds great.

  5. That was a fun experiment….we had the same reaction. I’m linking to your post on this one…forgot to get out my camera! Great pics/video! 🙂

  6. Pingback: Apologia Biology: Module 14 « Mindful Ramblings

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