Summer is the season for fireworks! Let’s mimic the fireworks you see in the air using materials from home to make a safer version in a jar!
A clear glass or jar (Plastic can be used as long as it is clear.)
A small bowl
2-3 tablespoons of oil (vegetable, coconut or whatever you have on hand)
Water-based food coloring in three colors
1. Add water to your glass or jar until it is about three-quarters full.
2. In a small bowl measure 2 tablespoons to 3 tablespoons of oil. You need enough to cover the water with a thin layer of oil.
3. Add about three drops of each color of food coloring. Drip them all around the oil so that each spot is separate from the others.
4. Use a fork to gently break up the food coloring drops in the oil.
5. Slowly, slowly, slowly pour the oil on top of the water.
6. Watch the fireworks begin!
How does it work?
Dissolving! Density! Diffusion!
Dissolving is when a substance breaks apart when it is mixed with another substance. The food coloring drops will dissolve in the water because they are both water-based. The food coloring drops do not dissolve in the oil because water and oil will not mix together. Why not? Because of density.
Density is how much space an object or substance takes up. The formula for figuring out an object's or substance’s density is its mass divided by its volume. We don’t need to do any math to see how density works with these fireworks though.
Water is more dense than oil, so it stays on the bottom of the glass. Oil is less dense than water, so it will float to the top of the water and stay there. Even if you shake up the jar to mix the oil and water together, once you set it down the oil and water will separate back to their own layers. Try it. When substances will not mix, scientists say they are “immiscible.”
So why do the food coloring drops move through the oil and then explode when they reach the water? What you are seeing is called diffusion.
Diffusion is when molecules move from an area of high concentration to an area of low concentration. We know that water is more dense than oil. Because the food coloring is water-based, it will slowly sink through the oil. The two substances are immiscible. But the food coloring and water will mix together and the food coloring will dissolve. Scientists would say the two substances are “miscible.”
Once the food coloring reaches the water it starts to dissolve and diffuse through the water. Changing the temperature of the water will change the concentration of the molecules. What happens to the fireworks if you use colder water? Warmer water? Try it and see!
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