Although many science fairs begin in middle school, the judging gets more competitive at the high school level. These project ideas will appeal to the interests of many high school students, and are interesting enough to appeal to the judges as well!
Building and Using a Calorimeter
Many high school students enjoy coming up with ideas that interest them because they can explore and investigate them on their own. One popular topic is the issue of weight loss and calories. If this interests you, you may be interested in making and using a calorimeter.
Begin making a calorimeter by suspending a small metal can of water inside of a large metal can, setting a piece of food on fire in the bottom of the large metal can, and measuring the temperature change of the heated water after the piece of food has finished burning. Try testing a peanut, a cooked bean, a piece of popcorn, or a cube of cheese to see which one burns the quickest. This is also a way to test how biomass energy can be produced. Looking at your science fair project from this perspective can turn it into a cutting-edge experiment about how we could use renewable energy. (See this article for more renewable energy science fair projects.)
How Fertilizers Affect Plants
Which factors of a plant does each fertilizer change? You can find out with this plant-related science project. Take a look at the active ingredients in each fertilizer to make sure that you are choosing different types. You may want to try out some organic fertilizers and those that claim to be better for the environment as well.
Plant several identical plants, one using no fertilizer, and the others each using a different type of fertilizer. (To make your results more accurate, use several plants for the control, and several plants for each type of fertilizer.) Every day, examine each plant's height, its number of leaves, the size of its flowers, and whether its fruit has ripened yet. Examining the differences between the plants (and taking averages of your data) can help you decide which type of fertilizer has the greatest impact on each of the tested factors.
Testing Water in Different Places
Polluted water is a serious concern in today's world. Some stellar science fair projects rely on testing different sources of water and identifying how healthy the water is - for drinking, for wildlife, or for other purposes.
To create a science fair project about water pollution, you first need to learn about the different components of water quality, such as pH level, salinity, and conductivity. Research as many of these components as possible, and then think of a hypothesis that you can test based on your research. For example, if you live near a stream, think about how the water upriver from a factory will differ from the water downriver from that factory. If you live near a large lake, think about how the water near the edges of the lake will differ from the water near the center of the lake. Alternatively, you could put some water into two different fish tanks, change some of the conditions in one of the fish tanks (e.g., add plants or fish), and see how those changes affect the different components of water quality.
How can you test water quality? There are basic water quality kits available online. See this article for more information on how to test water quality for a science fair project.