I'm glad you asked that. A science fair project is an entry in a science fair. Science fairs have been held annually at many schools around the country since the late 1920's. Regional fairs, located in all fifty states and several foreign countries, are affliliated with the ISEF and follow its rules.
Competition is stiff.
In order to win a spot at the regional fair, there may be several levels of local science fairs in which a student must compete. Form a Hypothesis - Answer your question with a hypothesis, i.e. what you think the outcome of your experiment will be.