Underwater Fireworks

With your kitchen as your lab and baking supplies as your ingredients, create your own underwater firework spectacular! These underwater fireworks go off because of density. Density means how much something weighs for a given volume of it. Denser things like iron and stone sink. Less dense things like wood and rubber float.

In this experiment, you use four different liquids with four different densities: oil, water, food coloring, and saltwater. The oil sits on top of the water because it’s less dense than water. The water sits on top of the saltwater for the same reason. Food coloring is denser than oil and a little bit denser than water, but it isn’t as dense as saltwater. When the drops of food coloring hit the dense saltwater, they disperse like exploding fireworks!

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Materials you'll need

Step-by-step tutorial

Step 1
Gather your materials.

Step 2
Pour salt into the bottle until there is a thin layer of salt on the bottom.

Step 3
Pour warm water into the bottle so that the bottle is about ¼ full. Mix the salt and water until all of the salt has dissolved and the water has cooled.

Step 4
Pour cold freshwater into the bottle until the water level is about ¾ high.

Step 5
Pour oil into the bottle, so that there is about ½” of oil floating on top of the water.

Step 6
Add a spoonful of oil into a small bowl followed by a few drops of food dye.

Step 7
Stir until the large beads of dye have broken up into a bunch of small beads of dye.

Step 8
Gently pour the mixture into the bottle. Then, watch as the food dye begins to seep into the water! What happens when it reaches the saltwater layer?

Learn more
You probably have lots of liquids with different densities in your home. With adult supervision, try mixing some together to see which float and which sink. You can use your discoveries to make more underwater fireworks or other density representations! Some good liquids to try are corn syrup, rubbing alcohol, dish soap, milk, maple syrup, honey, and lamp oil.