My son has always loved doing science experiments. In the summer we would look through the Sick Science! site and pick out some experiments to do. Sometimes it was an electricity experiment, other times chemistry. We were never disappointed.
The most difficult one we did was making Geode Eggs. The experiment itself wasn't difficult. We just had to wait a while before seeing the results. And waiting is not always easy. But it was worth the wait. We kept those eggs around for years.
If you enjoy science, you'll love the Sick Science! YouTube channel. If you try an experiment don't forget to blog about it and include a photo of your experiment!