Water fireworks are a safe and easy science project kids can enjoy any day of the year. The project uses edible kitchen ingredients and simple materials to make color “explode” in water, much like fireworks. Water fireworks also involve interesting science concepts, like density, diffusion, emulsion, polarity, and color theory.
Water Firework Materials
All you need is:
- Food Coloring
- Clear glass or jar
If you don’t have food coloring, you can substitute water colors or acrylic paint. What matters is that the color is water-based and not oil-based.
Make Water Fireworks in a Glass
There are two methods to try. The first one forms large “firework” shapes in the water.
- Fill a glass of water.
- Add a bit of oil.
- Drip food coloring onto the oil. You can use one color or multiple colors.
- If you like, use the tine of a fork to break drops into smaller ones.
The second method yields many smaller “fireworks.” It’s great for multiple colors.
- Pour a bit of oil in a small container.
- Drip food coloring into the oil.
- Use a fork to break the droplets and mix them. Don’t mix too much or all the colors will combine.
- Pour the oil and food coloring into a tall glass of water.
How Water Fireworks Work
Water fireworks illustrate several scientific concepts:
- Density: Density is the amount of matter in a volume. Oil is less dense than water, so it floats on it.
- Miscibility: Miscibility is another way of saying “mixability.” If two liquids are miscible, they mix together. Food coloring and water are miscible. If you stir the dye into water, it completely disperses in the liquid. Oil and water and immiscible. They don’t mix. So, oil floats on top of water and doesn’t mix with it.
- Polarity: Polarity is the main reason food coloring and water mix, but oil and water don’t. Polarity is a measure of the electrical charge distribution around a molecule. The charge is evenly distributed around nonpolar molecules. One part of a polar molecule has a partial negative charge, while part has a partial positive charge. The basic rule of polarity is that “like dissolves like.” So, polar liquids dissolve in other polar liquids. Nonpolar liquids dissolve in nonpolar liquids. Nonpolar liquids (like oil) and polar liquids (like water and food coloring) don’t mix.
- Emulsion: You can mix immiscible liquids. If the drops don’t separate, they form an emulsion. Mayonnaise is a familiar example of an emulsion. When you mix oil and water, they separate, but if the drops are small enough it takes a while. When you stir food coloring and oil together, the oil surrounds the food coloring droplets. Eventually, the food coloring droplets sink down to the surface of the water. They don’t disperse in water the same as if you just dripped food coloring into water because other tiny food coloring cells merge and release color. Some oil gets pulled down into the water and then rises back up.
- Diffusion: Food coloring spreads through water through a passive process called diffusion. This process still occurs in water fireworks, but the oil molecules sometimes get between dye particles and water, leading to a more interesting pattern.
- Colors: If you select the right food colorings, you can see how colors combine. Red and blue make purple. Yellow and blue make green.
Homemade Lava Lamp
Water fireworks imitate real fireworks. They can imitate a lava lamp too. Just drop an Alka-Seltzer tablet into the water. The bubbles add motion to the water fireworks, causing oil globules to rise and fall like lava.
From Science Project to Science Experiment
Take water fireworks to the next level by including the scientific method. First, make observations about the project. Next, think of a factor you can change and make a prediction or form a hypothesis about what effect you think the change will have. Conduct an experiment and see whether or not your hypothesis was supported.
Here are ideas of factors you can change (the independent variable):
- Does the temperature of the water affect how quickly water fireworks form or how far they spread?
- What happens if you mix food coloring with other substances? Good examples to try include 2% or whole milk (which contains some fat), juice, rubbing alcohol, and dishwashing liquid.
- What happens if you omit the oil and just drip food coloring into water?
- What happens if you change the size or shape of the glass?