Colour changing Christmas shapes

In another rehash of a previous activity (it could be a long few weeks/months in tier 4 lockdown here), we did some more colour changing with red cabbage.  The cooking liquid contains pH-sensitive anthocyanins, and I cut some Christmas shapes out of kitchen roll and  painted them with either bicarbonate of soda solution, citric acid solution (you could also use vinegar but this smells less!) or patches of each then left them to dry.  I left the gingerbread man shape unpainted so it would stay purple.

Kitchen roll shapes

I laid the shapes out on the table and gave both boys a paintbrush and pot of cooled red cabbage cooking liquid.  To make this, I chopped and microwaved the cabbage with some boiling water for 2 minutes). Both loved the colour changes - my 4 year old has done similar things before but still enjoyed discovering the colours as he painted and the little one (almost 2) was really excited.  

Painting nicely together!

I talked about the science behind it with my 4 year old, namely that I'd painted the paper with an acid and a base and that the purple colour of the cabbage changes to red with the acid and blue/green with the base.  For my 2 year old, it was more of an art and fine motor skill activity, but lots of fun for both and they actually sat at the table and concentrated on their own paintings without any squabbling!

The big one's finished shapes

I used the leftover red cabbage cooking liquid with the small one, giving him a kids pipette and letting him squirt it onto a little bicarb and citric acid on a clear plastic tray (with close supervision). He was particularly impressed when the blue and pink liquids started to mix and froth (there's a chemical reaction happening which makes carbon dioxide gas). But would either boy eat the cabbage...? Nope!