COMSTOCK PARK, Mich. — Our science experiment this week deals with water, oil and food coloring to produce what appears to be fireworks in a glass. This week's demonstration was conducted at Pine Island Elementary School in Comstock Park. The main science behind this water fireworks experiment is all about water density. All liquid based substances have different density levels. The lower the density, the chances are it will float to the top. That's what happens when oil and water are added together. The oil is lighter, or less dense, so it floats to the top and sits on the surface of the water.
This experiment requires a glass, water, oil (we used canola oil) and whatever type food coloring you want to use. Density is a measure of how much something weighs (its mass) by how much space it takes up (its volume). Simply add the droplet of food coloring in the oil and stir it. Then slowly and carefully pour it into the glass of water. Eventually, the colored droplets will slowly sink from top to bottom, giving off the appearance of fireworks with a trailing tail. Here's what's happening scientifically.
Oil and water don’t mix because the water molecules are more attracted to each other than to the oil. Plus, oil is less dense than water, which causes the oil to float on top of the water, creating two distinct layers.
Liquid food coloring is water-based, which is why it doesn’t mix with the oil even when you stir it. Instead the food coloring breaks up into small droplets which become temporarily suspended (floating) within the oil. These droplets are more dense than the oil (due to their water content), and so they gradually fall though the oil and enter the water. Some residual oil remains on the food coloring droplets as they enter the water, which slows the absorption of the color, creating long trails that resemble fireworks.
In weather, air has density too. Cold, dry air is more dense or heavier than warm, moist air. That means it sinks. Warm, moist air naturally rises, since it's lighter and less dense. This rising air motion can eventually cool, create clouds, and perhaps precipitation. So, density is very important. The same is true for water and oceans. Colder water is more dense than warmer water. It sinks to the bottom. Ocean current move the water from place to place. That's also why Meteorologists study fluid dynamics, because it behaves in much the same way as the air. Thermodynamics is also another area of study for Meteorologists.