At a Science Fair, there are many projects that students have made, and each project asks a scientific question.  The question is then answered by conducting experiments.  Before you do the experiment, you state what you hope to prove but doing experimentation.   Then you write down each step of the experiment and make a conclusion.  At the end of the project you state the result that was reached, and how that result answered the original question.  For help with picking the subjects or topics for your science fair, go to this site.  Here, you will find ideas and projects that make for an excellent experience.  It is hard work to put on a fair, but it is a great learning tool. http://www.scienceproject.com/