Testing for Acids & Bases
We LOVE experiments in our house so I duly set off in search of litmus paper (also called pH paper). None of the drug stores that I visited had it (actually some didn't even know what I was talking about).
So we dug deeper...
Did you know that Litmus paper is made using chemicals found in purple cabbage?!
So we stopped at our local organic vegetable stand at the Farmer's Market and bought a purple cabbage for $3.00
Daughter chopped up two cabbage leaves.
Then we covered the pot and brought it to a boil on medium high on the stove.
Once it was boiling we turned the stove down to low and kept it at a simmer for 30 minutes.
Then we removed it from the heat and let it cool to room temperature so we could work with it safely. (We actually forgot about it for about 2 hours.)
The cabbage was greenish and the water was purple. Now we strained the purple water into 2 clear glasses. (We used 2 glasses just in case we accidentally contaminated one glass of dye.)
Then we popped one cotton ball into the dye at a time and let it sink to the bottom by itself. Using tongs, we placed each cotton ball onto a clean plate.
Now we poured about 1 teaspoon of vinegar over one cotton ball... and 1 teaspoon of baking soda (bicarbonate of soda) over the other cotton ball.
Now remember this:
acids will turn blue litmus paper red and
bases will turn red litmus paper blue
The cabbage dye will turn red when exposed to acids and will turn blue when exposed to bases.
Here are a few more things we tried out that we have readily available in our house.
We added 1 tsp vinegar to one glass of dye and 1 tsp baking soda to the other glass of dye
Then we popped a cotton ball into each glass, let it soak up some liquid, and put it onto a plate.
Then we poured 1 tsp vinegar over the blue cotton ball and 1 tsp baking soda over the red cotton ball.
acids will turn blue litmus paper red and
bases will turn red litmus paper blue
I think we might have made our own home-made litmus paper!
And have a lot of fun! (Squeals of delight are usually a good sign.)
If you want to try this experiment at home you will need:
- safety glasses, gloves, and long sleeves
- 2 purple cabbage leaves (washed and chopped)
- a small pot with a lid
- a pair of tongs
- a couple glasses
- some plates (white works best to see the colour of the dye) Each thing you try will need its own separate plate
- some cotton balls
- various household cleaners or foods that you think might be an acid or base strong enough to change the colour of the dye.
You might notice that you have to work the liquid or powder into the cotton ball by squishing it with the tongs. Just wash the tongs thoroughly before moving onto the next thing you want to test.
(The cabbage is safe to eat afterwards if you want to try it. It can also go onto the compost pile if you don't fancy boiled cabbage.)