Create colorful “fireworks” in water with this simple Fireworks in a Jar science experiment! Using just a few kitchen ingredients, kids can explore density, oil and water, and liquid properties while watching streams of color burst through the water like miniature fireworks.
This easy science activity is perfect for 4th of July celebrations, New Year’s Eve, summer learning, homeschool, classrooms, or any time you want a quick, hands-on STEM project.
Fireworks in a Jar
- Grade Level: Pre-K to Elementary
- Concepts: Density, Oil and Water, Liquid Properties, Scientific Observation, Scientific Method
What Kids Will Learn
- Explore why oil and water don’t mix.
- Observe how density affects liquids.
- Discover how food coloring moves through oil and water.
- Practice making predictions and observations.
- Build science vocabulary through hands-on exploration.
Supplies
- Warm water
- Vegetable oil
- Liquid food coloring (3–4 colors)
- Large mason jar or clear glass
- Small bowl or cup
- Spoon or fork
🔎 Tip: Warm water helps the colors spread more quickly for an even better fireworks effect.
How to Make Fireworks in a Jar
STEP 1
Fill a clear mason jar about ¾ full with warm water.
STEP 2
Add 4 tablespoons of vegetable oil to a small bowl.
Add 4–5 drops of each food coloring to the oil.
Using a spoon or fork, gently stir just enough to break the food coloring into small droplets. Don’t overmix.
STEP 3
Slowly pour the oil mixture over the warm water.
STEP 4
Watch as the colorful droplets slowly sink through the oil before bursting into beautiful streaks of color when they reach the water.
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Think Like a Scientist
Before you begin, ask:
- What do you think will happen when the oil is poured into the water?
- Why doesn’t the food coloring mix with the oil?
- What happens when the droplets reach the water?
- Does warm water change the results?
- What if you only use one color?
Encourage kids to make observations using words like density, float, sink, mix, separate, and dissolve.
The Science Behind It
Why does Fireworks in a Jar work?
Oil and water don’t mix because they have different molecular structures. Water molecules stick together, while oil molecules stick together, creating two separate layers.
- Oil is less dense than water, so it floats on top.
- Food coloring is water-based, so it doesn’t dissolve in the oil. Instead, it forms tiny droplets that slowly sink because they are denser than the oil.
Once the droplets reach the water, they dissolve immediately and spread into colorful streams that look like fireworks.
💡 Fun Fact: Warm water helps the colors spread more quickly because the water molecules are moving faster than they do in cold water.
Extend the Activity
Turn this experiment into a simple science investigation by testing one variable at a time. This is a fantastic opportunity to use the scientific method with kids.
Try:
- Warm water vs. cold water
- Different cooking oils
- One color vs. multiple colors
- Different container sizes
- Mixing with an eyedropper instead of stirring
🔎 Record your observations and compare your results.
Frequently Asked Questions
Why don’t oil and water mix? Oil and water have different molecular structures. Water molecules are attracted to one another, while oil molecules stick together, so the two liquids naturally separate into layers.
Why does the food coloring sink? Food coloring is denser than the oil, so gravity pulls it through the oil until it reaches the water, where it dissolves.
Does the experiment work with cold water? Yes! The colors will still spread, but usually more slowly than they do in warm water.
Can I use gel food coloring? Liquid food coloring works best because it mixes into the water more easily than gel food coloring.
What age is this experiment best for? This activity is ideal for preschool through elementary students. Younger children enjoy watching the colorful reaction, while older kids can investigate density and design extension experiments.
Can I make this a science fair project? Absolutely! Test one variable at a time, such as water temperature, oil type, amount of food coloring, or container size, and record your results.
More 4th of July Science Activities
Continue the fun with these patriotic STEM projects:
👉 Find 15+ 4th of July Science and STEM activities here
More to Explore
Keep the science fun going with these related activities:
- Oil and Water Experiments – Explore more activities featuring liquids that don’t mix.
- Density Experiments – Discover colorful ways to investigate floating, sinking, and density.
- Kitchen Science Experiments – Turn everyday ingredients into exciting science.
- Summer Science Experiments – Find more easy STEM activities for summer.
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