25 Science Fair Ideas for 9th Grade (With Project Tips)

In 9th grade, science fairs are a great way to go beyond textbooks and start thinking like a real scientist. It’s no longer about baking soda volcanoes—it’s about exploring ideas, asking smart questions, and solving real-world problems through experimentation. But where do you start?

These 25 science fair ideas for 9th grade cover a range of subjects—from biology and chemistry to psychology and tech—and they’re designed to challenge your thinking while still being manageable. Each category below includes not just project suggestions, but context to help you choose the right fit.

🔬 Biology & Environmental Science Projects

Why it works for 9th grade: Biology encourages observation, analysis, and an understanding of the living world. Environmental topics also help students see the impact of science on daily life and the planet.

These projects allow students to explore plant life, soil quality, sustainability, and living systems—all using materials that are affordable and easy to access.

1. Do plants grow faster under natural light or LED light?
   Investigate how different light spectrums affect photosynthesis by growing the same plant under varying light sources.
2. Can music affect plant growth?
   Explore how sound vibrations or genres of music may influence plant height or health over time.
3. How do different liquids affect seed germination?
   Test how water, milk, juice, or soda influence how fast seeds sprout and how healthy they grow.
4. How effective are natural fertilizers versus synthetic ones?
   Compare the growth of identical plants using compost, manure, and store-bought fertilizer to determine which supports better growth.
5. What’s the best method for filtering dirty water?
   Build and test water filtration systems using sand, charcoal, and other simple materials to see which produces the cleanest result.

⚗️ Chemistry Projects

Why it works for 9th grade: Chemistry is all about reactions and transformations. These projects allow students to visually and measurably explore how substances change and interact, while introducing safety-conscious experimentation.

Projects in this category typically involve kitchen-friendly chemicals, safe acids and bases, and measurable reactions—all ideal for young scientists ready to level up.

6. Which antacid neutralizes stomach acid best?
   Simulate stomach acid using vinegar and test different over-the-counter antacids to measure which one changes pH fastest.
7. Do different cooking oils have different smoke points?
   Use a thermometer to determine when various oils begin to break down, creating a chemistry and culinary crossover.
8. What’s the best way to prevent fruit from browning?
   Investigate the effectiveness of lemon juice, sugar water, saltwater, and refrigeration on preventing oxidation.
9. How do temperature changes affect the rate of chemical reactions?
   Use simple reactions like baking soda and vinegar at different temperatures and record the speed and volume of gas produced.
10. Can you create a homemade pH indicator from red cabbage?
    Extract anthocyanin from cabbage and test household liquids to see color changes based on acidity or alkalinity.

🧲 Physics & Engineering Projects

Why it works for 9th grade: Physics and engineering emphasize motion, force, energy, and design. These hands-on projects foster critical thinking and show how math and mechanics intersect with real-world applications.

Whether testing flight, force, or construction design, these projects push students to build, measure, and problem-solve in creative ways.

11. What angle gives a paper airplane the longest flight?
    Explore how launch angle affects flight distance and stability. Great for demonstrating projectile motion.
12. Which bridge design holds the most weight?
    Build bridges using popsicle sticks or straws and test different shapes to learn about structural engineering and stress points.
13. Can magnets affect the speed of falling objects?
    Explore magnetic braking using magnets and metal tubes—an intro to electromagnetic force in action.
14. How do different surfaces affect friction?
    Slide objects on a variety of materials (carpet, tile, sandpaper) to calculate resistance and energy loss.
15. Can wind power light up an LED?
    Design a small wind turbine to generate enough energy to light a bulb, teaching energy conversion and renewable power.

💻 Technology & Computer Science Projects

Why it works for 9th grade: Technology and coding are increasingly important. These projects let students think like digital creators while exploring data, automation, and security—using tools they likely already have access to.

With free software and basic programming skills, students can test how technology works—and where it can be improved.

16. Which search engine gives the most accurate results?
    Use identical queries on different platforms and score based on relevance, speed, and ad ratio.
17. How secure are common passwords?
    Research password types and test them using password strength tools or simulated cracking programs.
18. Do different fonts affect reading speed or memory?
    Have participants read and recall passages written in different fonts. Track speed and accuracy.
19. Can AI image filters recognize emotions accurately?
    Use AI-based software to analyze photos of emotional expressions and compare results to human interpretation.
20. How do different coding languages compare in speed?
    Write simple programs in Python, JavaScript, or C++ and test which one executes tasks faster.

🧠 Psychology & Behavior Projects

Why it works for 9th grade: Psychology experiments help students understand how people think, feel, and behave. It’s also one of the most accessible science fair categories—you just need willing participants and a survey or test format.

These ideas can be done with peers, parents, or volunteers and help students build skills in observation, analysis, and ethical testing.

21. Does background music affect study focus?
    Measure how students perform tasks with silence, classical music, or lyrics playing in the background.
22. Are people more honest when anonymous?
    Use a simple survey on a sensitive topic and compare results when names are attached vs. anonymous.
23. Do colors affect mood?
    Show participants various colors and use surveys to gauge how the colors influence feelings or energy levels.
24. How does social media scrolling affect attention span?
    Have subjects complete tasks before and after scrolling through social media. Track concentration levels.
25. Does multitasking reduce performance?
    Ask participants to complete puzzles or memory tasks with and without interruptions, then compare results.

🛠️ Practical Tips for Science Fair Success

Choose something meaningful: Pick a topic that’s interesting to you personally. When you’re excited, your enthusiasm will show in your work and presentation.

Form a testable question: Your project should be based on a question you can answer through experimentation and observation—not just a demonstration.

Document everything: Keep a lab journal with your hypothesis, materials, methods, and results. Judges want to see your process, even more than a perfect outcome.

Be ready to explain your “why”: Know why you picked the topic and what you learned. Science fairs reward curiosity and understanding, not just results.

Practice your presentation: Whether it’s for your class or a panel of judges, rehearse how you’ll explain your project clearly and confidently.

Final Thoughts

Science fair projects in 9th grade offer a powerful chance to ask bold questions, solve real-world problems, and think like a scientist. The ideas above are flexible enough to explore in depth while being doable for students working solo or in small teams.

Pick a project that speaks to your interests, stick to the scientific method, and don’t be afraid to be creative. Whether you’re measuring plant growth or investigating attention spans, your curiosity is the key ingredient. Let that shine—and your project will too.