Make some truly amazing, magic colour changing potions in this brilliant science activity for kids! Perfect for the classroom, home school, science fair projects or a rainy day activity for all ages to enjoy together.

This magic colour changing potions science activity is a true classic and one we have had on our must-do list for years. We have a well-loved copy of 365 Science Activities Book and the kids have turned over the corners of all of their favourites, which we pull out and work our way through in our after school or weekend fun times.

For this magic colour changing potions experiment you will need:

one red cabbage

bicarbonate of soda (baking soda in the US)

vinegar

clean, empty jam jars

water

spoons

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Instructions:

Firstly you need to make the cabbage water. We poured boiling water over a whole, small red cabbage in a bowl and left it to steep in the water for about half an hour. Then we simply poured it through a sieve and collected the water into a large jug.

How much water you decide to use will depend on how many times you want to try the experiment and how intense you wish the colour to be. We used one kettle full of water, approximately.

I was expecting the water to be purple, but it was very blue instead! I don’t know if this was something to do with the type of cabbage we used but the experiment worked very well regardless. Yours may be purple when you make it- let me know!

Into four empty jam jars I tipped the cabbage water and then added varying amounts of water to dilute it, so that it ranged in colour intensity. We simply did this so that it would be a nice visual comparison.

Ready to go!

Next, the kids each took it in turns to make some magic happen and they were each wowed as they did so (me too!)

Watch our video here! It is really much more amazing to watch it happen before your eyes:

Add a small amount of vinegar to the blue cabbage water and it instantly turns pink! Because of the varying degrees of dilution, we had a lovely range of pink hues as a result.

Next we added some bicarbonate of soda (baking soda) to the (now pink) water and watched in awe as it bubbled up and turned purple! Again, the range of hues was gorgeous.

We decided to continue adding the two ingredients one after the other to see what effect they might have. So after the vinegar and bicarbonate of soda, we then tipped out a little of the liquid and then added more vinegar again. This time it turned from bright pink to a gorgeous range of purples! They really enjoyed the role of potion makers and turned it into an imaginative play game, similar to our Harry Potter potions class we did last year.

Then they simply enjoyed adding and mixing the ingredients freely to see how many different colours they could create. The range was gorgeous!

They could have happily enjoyed this activity all day and I think we will have to do it again soon, this time perhaps adding a couple of new ingredients.

So, what’s the science behind the fun and magic of the colour changing “potions”?

It’s actually pretty simple to explain although younger kids won’t yet understand the meaning of some of the more scientific words.

Cabbage water = an indicator

Vinegar = an acid

Bicarbonate of Soda (baking soda) = an alkaline

The cabbage water is an indicator which can show how acid or alkaline a liquid is when it is added to it. A chemical reaction takes place which causes it to change colour. Scientists take this one step further and use PH test strips to dip into liquids and take a look at the colour which shows up.

You could think up more liquids which are acids and alkalines and experiment with using them, seeing what effect they may or may not have. Try using water and other PH neutral liquids to see if anything happens when they are added too.

I have read that Milk of Magnesia and washing up liquid turn the original cabbage water green as they are bases! We are trying that next and may make another video to add alongside this one in this post. Watch this space.