Learning about chemistry with purple cabbage

We started a series of video looking at acids and bases. Fittingly we used purple cabbage as our pH indicator.

What I love about the first video is that Matthew eats the cabbage during it - this really highlights the important point that everything is made up of chemicals (currently a very 'dirty' word).

Comments

Dry ice and pH

I have to admit that the colour change was not a pronounced as I was hoping for with carbon dioxide dissolving to form carbonic acid. In the past I have used other pH indicators which give a much bigger colour change. This is due to the relative high pKa of carbonic acid ~ 6 in contrast to acetic acid in vinegar (pKa ~ 4). I’m keen to repeat this using a different indicator and possibly just blowing into a solution using exhaled carbon dioxide to change the pH. This is a very important demonstration as it simply shows the effect that our carbon dioxide emissions have on the pH of the ocean. Acidification of the oceans is a topic that has not really been raised in the climate change debate but a very serious problem that is looming...

pH in the kitchen

We extended our learning about acids and bases to the pH scale. I intentionally did not over edit the video video because it really shows the learning process so the video is longer than normal. By the end of the video Matthew was better at matching the pH paper against the pH chart than I was. Matthew also introduced the video with out any prompting from me - he's picking it up quickly. Again using the A, B and N tabs really seems to have helped provide a framework for learning. Make sure you watch till the end. Matthew spontaneously started writing down all that we had been going through. It was almost like he was writing up his lab book. I could learn some lessons from him!!

Reflections of a chemical dad

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