There are plenty of different chemistry science fair project ideas to choose from that will both be interesting to the student and allow them to understand the principles of this science. Obviously, the level of understanding will play a role in how advanced the project should be, otherwise the student will either be too bored or confused. If the student is in middle school, from seventh grade to the 9th grade, then they may enjoy an experiment involving metal. Considering all the different properties and types that there are in nature, testing which type of metal protects against radiation the best is a good idea to present at a fair.
Another idea with metal is to consider testing which lubricants are the most effective at reducing friction on the different surfaces. The results of this kind of experiment would be very interesting to see at a chemistry science fair. Of course, if the students are in high school, then they might consider doing something a little more advanced, such as testing how hydrochloric acid reacts with the different types of metals. Other ideas that aren't related to metals include biomass and fuels. A great experiment would be to test which types of oils are the most effective at powering lawn equipment.
Students might be interested in experiments that deal with physics and research. One great example is the project of building a biomass generator. This would make a fantastic group project that would attract plenty of attention at any chemistry science fair and is possible for students in middle school or high school to complete. Experimenting with salt is always interesting as well, and a great idea is to see just how much salt is required to make different objects float. It can also be compared to sugar by testing which substance dissolves more quickly in certain liquids.
The key to a good chemistry science fair project is one that will be both interesting to the person doing the experiment and the ones that will view it on display. Different students will have varying tastes in regards to what is entertaining and what isn't, but fortunately there are more than enough ideas to choose from.