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. 🙂