One of my daughters had the following assignment for science. First you boil a couple leaves of red cabbage and pour off the water. In our case the water was inky blue, but the results may vary according to your water chemistry and possibly by your cabbage. Next add a little diluted ammonia to the water and the color will change. Add the right amount of vinegar and it will change back to the original color. Add more vinegar and it will turn a new color. The liquid can turn a wide spectrum of colors. (Which colors? You’ll need to do the experiment to find out!)
Now we’ve got a jug of ammonia left over. What can you do with a jug of ammonia? Any practical uses? Fun uses? Any more science demonstrations?