One idea for a ninth grade science fair project is to explore how exposure to different chemical compounds affects the germination rate of seeds. Another idea is to explore different materials and construction that reduce noise pollution in a room or building.
One topic to explore for a ninth grade science fair is whether or not eye color determines the scope of a person's peripheral vision. The hypothesis is that people with a darker iris color have pupils that widen more to red light. The question to answer is whether or not a widened pupil leads to better peripheral vision. This project requires multiple test subjects with several different eye colors. It is important to record the field of vision observed from each subject in varying degrees of light saturation to get an accurate answer to the hypothesis.
Another project explores how a magnetic field affects living organisms. The test subjects would be small animals, such as brine shrimp or fruit flies. Materials include strip magnets and containers for the test subjects. There are two or more groups of subjects tested to make note of the differences and similarities of each test group. One group would not have magnetic strips attached to the containers, while the other group would. Any other groups might test the affect of varying distances of magnetic field exposure.