There are a lot of educational sites out there with project ideas. If your child doesn’t have something in mind, do some online research and look for an experiment on a topic that your child is interested in. A lot of sites include instruction cards and materials lists to help you set up a successful experiment. That said, we have a few words of caution about the online resources:
As mentioned up top, some of the ‘experiments’ are more like science demonstrations, so make sure to either adapt to it or find another option that your child can use to compare results.
A lot of the project idea boards I found gave the “answer”, which may be helpful to you as a parent (or teacher) but takes away from your child’s scientific experience, so you might consider keeping that part to yourself.
Do your own research: there are few examples where the experiment is sound, the instructions are good, but the background information is inaccurate or outdated, so proceed with caution and remember that science moves quickly.