Science fairs are an exciting way for 4th graders to unleash their creativity, test cool ideas, and dive into hands-on experiments. From making a volcano erupt to growing crystals right at home, there’s no shortage of fun ways to explore the world of science. The best part? These projects don’t just impress judges, they spark curiosity, build problem-solving skills, and make learning feel like an adventure. In this guide, we’ll share some of the best ideas for 4th-grade science fair projects that are easy, engaging, and guaranteed to make science fun!
5+ 4th grade Science fair projects
Need an awesome idea for a science fair project but not sure where to start? We’ve rounded up five of the best 4th grade science fair projects that are fun, easy, and sure to impress. Let’s dive in and find the perfect experiment for your big day!
1. The classic volcano eruption
The volcano eruption experiment is a science fair favorite because it’s easy, exciting, and teaches kids about chemical reactions. When baking soda and vinegar mix, they create carbon dioxide gas, leading to a fun, foamy explosion!
What you’ll learn:
- How chemical reactions work (acid-base reaction)
- How carbon dioxide gas causes bubbling and fizzing
- The basics of real volcanic eruptions (though the real ones involve molten rock, not baking soda!)
Materials:
- Small plastic bottle (or a volcano model)
- 2-3 tbsp baking soda
- ½ cup vinegar
- Dish soap (optional, for extra foam)
- Red/orange food coloring
- Tray or plastic sheet (to catch the mess)
Instructions:
- Build the volcano – Place a plastic bottle on a tray and shape a volcano around it using clay or papier-mâché.
- Add baking soda – Pour baking soda into the bottle. Add dish soap for more foam.
- Mix vinegar & color – In a cup, mix vinegar with food coloring.
- Make it erupt! – Pour the vinegar into the bottle and watch the lava flow!
2. Growing crystals at home
Growing crystals is a fun and easy science fair project that demonstrates how dissolved substances form solid structures. This experiment teaches kids about solubility, evaporation, and crystal formation while creating beautiful, sparkling crystals.
What you’ll learn:
- How solubility works and why substances dissolve in water
- How evaporation causes crystal formation
- The science behind growing different types of crystals
Materials:
- 1 cup hot water
- ½ cup salt or sugar
- A jar
- String and pencil (or pipe cleaner)
You can use a printable experiment log from Worksheetzone to track your crystal growth progress.
Instructions:
- Dissolve the salt/sugar – Stir salt or sugar into hot water until no more dissolves. This creates a saturated solution.
- Prepare the jar – Pour the solution into a jar. Tie a string to a pencil and place it across the jar so the string hangs inside.
- Let it sit – Leave the jar undisturbed in a warm spot for several days.
- Observe crystal growth – As the water evaporates, crystals will start forming on the string!
3. Balloon-powered car
This exciting experiment demonstrates Newton’s Third Law of Motion: for every action, there is an equal and opposite reaction. By using air pressure from a balloon, kids can build a simple car that moves without a motor!
What you’ll learn:
- How air pressure creates movement
- The basics of Newton’s Third Law of Motion
- How force and friction affect speed
Materials:
- A small cardboard or plastic base (for the car body)
- 4 bottle caps (for wheels)
- 2 straws (one for axles, one for the balloon)
- Wooden skewers (for axles)
- A balloon
- Tape and scissors
Instructions:
- Build the car base – Attach the bottle caps to the ends of the skewers to create wheels, then secure them under the car body using straws as axles.
- Attach the balloon – Tape one end of a straw inside a balloon and secure the other end to the top of the car.
- Inflate the balloon – Blow air into the straw to inflate the balloon, then pinch it shut.
- Let it go! – Release the balloon and watch the car zoom forward as the air rushes out.
4. Water filtration experiment
This experiment teaches kids how filtration works by removing dirt and impurities from water. It’s a great way to explore environmental science and the importance of clean water.
What you’ll learn:
- How filtration removes particles from water
- The role of different materials in water purification
- The basics of environmental science and clean water technology
Materials:
- A plastic bottle (cut in half).
- Sand.
- Gravel.
- Activated charcoal (optional for better filtration).
- Coffee filter or cotton balls.
- Dirty water (mix water with soil or food coloring).
Instructions:
- Build the filter – Place the top half of the bottle upside down inside the bottom half.
- Layer the materials – Add layers in this order: coffee filter/cotton balls, charcoal, sand, and gravel.
- Pour in dirty water – Slowly pour dirty water through the top and watch it filter through the layers.
- Observe the results – Collect the filtered water in the bottom half of the bottle and compare it to the original.
5. Can plants grow without soil?
This experiment explores hydroponics, a method of growing plants without soil. It helps kids understand how plants absorb nutrients and the role of water in plant growth.
What you’ll learn:
- How plants can grow without soil using hydroponics
- The importance of water and nutrients in plant growth
- How roots absorb nutrients from different sources
Materials:
- Bean seeds
- Cotton balls or paper towels
- A clear jar or plastic cup
- Water
Instructions:
- Prepare the growing base – Place damp cotton balls or a folded wet paper towel at the bottom of the jar.
- Add the seeds – Place the bean seeds on top of the cotton, ensuring they touch the moisture.
- Keep it moist – Add water as needed to keep the cotton damp but not soaking.
- Observe the growth – Place the jar near sunlight and watch the seeds sprout and grow without soil!
Help your students put their science fair ideas into action! Browse our collection of engaging 4th grade science worksheets — perfect for experiments, data recording, and hands-on learning.
FAQs
1. What are some good science fair project ideas?
Great science fair projects for 4th graders should be simple, fun, and educational. Here are a few ideas:
- Volcano eruption – A classic experiment demonstrating chemical reactions.
- Balloon-powered car – Teaches Newton’s Third Law of Motion.
- Growing crystals – Shows how solubility and evaporation work.
- Water filtration experiment – Demonstrates how water is purified.
- Magnet strength test – Compares how different surfaces affect a magnet’s pull.
- Static electricity with balloons – Explores how charged particles attract objects.
2. What are 4th Grade science fair projects with plants?
Plant-based experiments are great for teaching biology and environmental science. Here are a few ideas:
- Can plants grow without soil? – A hydroponics experiment showing how plants absorb nutrients from water. Recommendation: Printable Nutrient Cycles Worksheets
- Do plants grow better in sunlight or artificial light? – Compares plant growth under different light sources.
- How does music affect plant growth? – Tests whether plants grow differently when exposed to music.
- Watering plants with different liquids – Observe how plants react to water, juice, soda, and other liquids.
- The effect of pH on plant growth – Uses acidic and alkaline water to see how plants respond.
Final thoughts
Science fair projects don’t have to be rocket science, unless you’re launching a homemade rocket! These 4th grade science fair projects are fun, easy, and a great way to wow your classmates (and maybe even the judges). So grab your lab coat (or an old T-shirt), gather your materials, and get experimenting. Who knows? You might just be the next Einstein or at least the kid with the coolest project at the fair!
