WORLD OF SCIENCE (CBS46) -- In today's experiment we will explore density by making a rainbow in a jar! 

MATERIALS NEEDED:

  • Clear glass jar
  • 1/4 cup of honey
  • 1/4 cup of blue dish soap 
  • 1/4 cup of water
  • 1/4 cup of vegetable oil 
  • 1/4 cup of rubbing alcohol 
  • Red, blue, and red food coloring

Before you start the experiment, hypothesize which ingredients will be the heaviest and which will be lightest. 

1. Pour the honey into the clear glass jar. Add one drop of red and blue food coloring. Mix until the honey turns purple. 

2. Next, slowly pour the dish soap on top of the honey. Notice how the two don't mix. 

3. Add one drop of green food coloring to the water and mix. Slowly pour the water on top of the dish soap in the jar. Make sure you pour carefully so that you don't get bubbles from the dish soap and water interacting. 

4. Next, add the vegetable oil to the jar. Again, pour slowly to avoid too much disturbance to the other layers. It helps to tilt the jar slightly as you pour in the vegetable oil. 

5. Add one drop of red food coloring to the rubbing alcohol. This is the trickiest layer to add. A turkey baster works best to add the alcohol to the jar. However, if you don't have a turkey baster, the slow pour method works as well. 

EXPLANATION: 

We were able to create a rainbow in a jar because each one of the ingredients has a different density. Density is determined by mass and volume: the mass of the molecules and how tightly packed they are in an object or liquid. The lighter liquids like the oil and rubbing alcohol are less dense. The molecules are not as tightly packed together. The heavier liquids like the honey and dish soap are more dense. The molecules are tightly packed together. 

If you want to take it another step further, try dropping different objects into your density rainbow. Try a plastic cap, cherry tomato, olive, screw, etc. Notice which layer of the rainbow the objects fall to -- do they float or sink? If the layer is more dense than the object, the object floats on that layer. 

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