Astronomy
Project Ideas : Questions stating an independent and a dependent variable about astronomy topics.
Project Topics: How to Use Astronomy Facts to Develop a Science Fair Project
More Astronomy Science Project Ideas
Insolation : This link provides information about insolation only, but you could easily design an investigation in which you would mathematically compare insolation for solar-rays at different angle, and then design an investigation to experimentally measure the insolation. Percent error for the investigation could be calculated using the math calculations as the standard.
Biology
DNA Extraction Index : This link provides a list of different investigations and research material about extracting DNA.
Oxidation of a Sliced Apple : This links to research about the browning of a sliced apple. Tips for a project are given in the related topics.
Chemistry
Crystal Formation : Knowing about crystals could help in designing a crystal project.
Slime: Polymers Index : Find ideas for making different kinds of slime as well as ideas for developing the making of slime into a science fair project.
Physics
Inertia Used to Measure Mass : This information could be used to design a science project.
More Ideas About Making and Using an Inertia Balance
Scientific Method: Color Mixing : A brief overview of using color mixing for a science project.
Surface Tension : Ideas for designing and developing a science fair project about surface tension.
Miscellaneous Ideas
Emma Gets Started on Her Science Fair Project
https://scienceprojectideasforkids.com/2011/science-fair-p…to-get-started/