Many good ideas for science projects are online and in books. Just make sure that you credit your sources. You should not copy an experiment but instead, find a way to make it your own.

Demonstrating that you understand how to conduct an experiment or use the engineering design process is important to reviewers. For an experiment, find out why a hypothesis cannot be “proven” and how to create a testable hypothesis. Learn about how to design an experiment. What is a control? Do you need to perform more than one trial?

There are several good websites such as: www.sciencebuddies.org, At https://www.stevespanglerscience.com/2012/01/16/science-fair-911-demonst..., you will find a discussion of the difference between a science demonstration and an experiment and how you may turn a demonstration into an experiment.

Parents and teachers may find www.teachengineering.org helpful for engineering design projects.