Why Don't Water and Oil Mix? | Colorful Bombs

Total Time: 5 minutes to infinity

Safety Concerns: None. All materials are nontoxic and edible!

Materials You Need:

Clear glass or plastic cup(s), half full of water

Vegetable oil

Food coloring


  • Pour enough oil in each glass to make a thin layer of oil on top.
  • Drop 1-5 drops of food coloring in each cup. The food coloring will bead and sit in the oil layer.
  • Wait and watch for a minute or two for the food coloring to drop from the oil layer to the water layer. Bombs away!

Oil is made up of different chemical bonds than water is, which is why the two don't mix. (Water is polar, oil is nonpolar, in case you wanted to know.) Oil is less dense than water so it floats on top. The food coloring only dissolves in water since it is water-based. When you drop the food coloring into the cup it beads and sits on the oil layer until gravity finally wins and it drops down to the water layer creating the exciting "bomb" effect.

Watch as the color slowly disperses through the water. Molecules are always in motion, which you can see as the color mixes with the water without any outside stirring. Try stirring the mixture and notice what happens. No matter how much the mixture is stirred the oil will always form a layer on top while the colored water remains on the bottom. If your child is like mine they will want to do this experiment over and over again with different colors!

One note: Sometimes it takes several minutes for the colors to drop into the water. Some kids are patient and are willing to wait. Some, like my two-year-old, can't wait for longer than a few seconds. Feel free to spin the glass a little bit to get the color to drop a little bit sooner :)

Want another variation of this experiment? Try our super simple Lava Lamp using these same materials!