It can be a challenge to come up with a science fair project idea. There is fierce competition to come up with the coolest idea, plus you need a topic that is considered appropriate for your educational level. I've arranged science fair project ideas by topic, but you might like to take a look at ideas according to education level.

• Free Elementary School Projects
• Free Middle School Projects
• Free High School Projects

A high school sciencefair project usually involves an experiment, an invention, or a relatively sophisticated model of a phenomenon. Look at topics addressed by others and ask yourself what questions are left unanswered? How could they be tested? Look for problems in the world around you and try to explain them or solve them.

• Identify common household products that pose a risk to the environment.
• Which type of light bulb is the best in terms of cost? Which is the most friendly to the environment?
• Are night insects attracted to lamps because of heat or light?
• Can you identify any natural mosquito repellents?
• Does magnetism affect the growth of plants?
• Does storage temperature affect the pH of juice?
• Does the presence of cigarette smoke affect the growth rate of plants?
• Does eating breakfast have an effect on school performance? Does it matter what you eat?
• Do the same types of mold grow on all types of bread?
• Does light affect the rate at which foods spoil?
• Do foods containing preservatives stay fresh longer than foods without them?

• How does time or season of harvest affect the chemistry and nutritional content of food?
• How long do home haircoloring products hold their color? Does brand matter? Does type of hair affect colorfastness? How does previous treatment (perming, previous coloring, straightening) affect initial color intensity and colorfastness?
• Do all dishwashing detergents produce the same amount of bubbles? Clean the same number of dishes?
• Is the nutritional content of different brands of a vegetable (e.g., canned peas) the same?
• How permanent are permanent markers?
• Do plant-based insect repellents work as well as synthesized chemical repellents?
• What are some natural ways to color food?
• Is laundry detergent as effective if you use less than the recommended amount? More?
• Is bottled water more pure than tap water?
• What type of invisible ink is the most invisible?
• How does the pH of juice change with time?
• Do all hairsprays hold equally well? Equally long? Does type of hair affect the results?
• How does the rate of evaporation of the crystal-growing medium affect the final size of the crystals?
• You will usually heat water or another liquid to dissolve a solid to grow your crystals. Does the rate at which this liquid is cooled affect the way the crystals grow?
• What effect do additives have on the crystals?
• How do different fertilizers affect the way plants grow?
• What chemical is best at melting ice from a walkway or road?
• Does using colored mulch have an effect on a plant?
• How do different factors affect seed germination? Factors that you could test include the intensity, duration, or type of light, the temperature, the amount of water, the presence/absence of certain chemicals, or the presence/absence of soil. You can look at the percentage of seeds that germinate or the rate at which seeds germinate.
• How are plants affected by the distance between them?
• How heavy is the average backpack at school when a student brings it in?
• How do various chemical treatments affect seed germination rates?
• What conditions affect the ripening of fruit?
• How much of your household waste can you turn into compost?
• What type of shoe sole get best traction? Is more slippery?
• How are different soils affected by erosion?
• Do people who exercise a lot eat the same number of calories as those who exercise less?