The Royal Institution of Great Britain has introduced a series of experiments for kids.
Here are the ones I like the most.
The next one can be turned into a nice experiment. Try for instance collecting water from different sources and test which one is more acid. Then try watering plants with them and see which plant grows more.
This is a nice variation of the water rockets experiments… with low level risk.
Nice an easy electricity experiments.
The final “lava lamp” is awesome.
The last one….