Red cabbage colours

My almost 2 year old seems to have been wowed by some of the colour changing activities (fairy light pictures and Christmas shapes) that we tried in December and he keeps asking to "do some science".  We're very slowly eating our way through a red cabbage (and by we, I am not including the boys...) and so I keep saving some of the cooking liquid for some pH-dependent colour changes.

Ready to go!

The activity with the red cabbage that has gone down best with both boys was one using some plastic packaging as a tray with multiple compartments.  The packaging I used was from Hot Wheels cars (which have really quite excessive packaging but at least it got some more use on its way to be recycled) although there are lots of other options e.g. trays from boxes of chocolates.  I put acid in some sections of it - I used vinegar and citric acid, other options would be lemon juice and sherbet - and some base (bicarbonate of soda) in others, left some empty and put water in a couple of others.  The idea was that the boys would discover whether they made an acidic, neutral or alkaline solution with the red cabbage by seeing the colour.

Different colours!

My 4 year old is pretty familiar with red cabbage as an indicator, but still enjoyed the anticipation of which colours he would discover.  I think the concept of acids and bases is lost on the 2 year old, but he also loved to guess what colour he would make, and then find out by squirting some red cabbage liquid.  We've got learning resources twisty droppers (affiliate link), which he's just figured out how to use properly, but you could have some small yoghurt pots to pour from if you haven't got any kids' pipettes.

Chemical reactions give bubbles and neutral purple

After all the compartments had red cabbage liquid added and they had made a range of colours from green-blue to pink, they decided to try mixing the different solutions.  My 4 year old knew that if he mixed an acid and a base he'd get some fizzing (chemical reaction which makes carbon dioxide), and my nearly 2 year old loved the bubbles.  He tried to find combinations that fizzed too, and it was more of an investigation for him as he tried different combinations, some which fizzed and others which didn't (e.g. adding water to either acid or alkali or adding acid to acid).  The big one had enough after a few fizzes, but the little one kept going until the whole tray, and most of the table, was purple!