Wikijunior talk:Big Book of Fun Science Experiments/Acid Investigations

While the lemon juice does change the milk, I don't think this is quite an appropriate experiment due to safety. Adding lemon juice (or any acid to milk) will cause the milk to curdle - thus when the kids drink the milk afterwards, they are drinking curdled milk. Not the most safe thing to do. This experiment would be more appropriate if the kids used some sort of indicator (like the red cabbage indicator) and then observed the change in color. Or, just observe and watch as they add enough lemon to make the milk get chunky.