Rainbow Liquid Density Tower

What you need

• Clear cups, 1 tall clear glass, plus small cups for measuring
• Dish soap, 2 tablespoons
• Water, 2 tablespoons
• Cooking oil, 2 tablespoons
• Food coloring, a drop for the water plus a different color for the alcohol
• Honey, 2 tablespoons
• Corn syrup, 2 tablespoons, or maple syrup
• Rubbing alcohol, 2 tablespoons, for a grown-up
• Spoon, 1
• Measuring spoons, 1 tablespoon
• Small objects, a grape, a coin, a bead and a bit of pasta
• Towel, 1, or a tray

How to do it

Grown-up prep: Set everything on a tray near a sink. Rubbing alcohol is for grown-ups to pour and keep away from faces and flames. Nothing in the glass is for drinking.

1. Pour the honey into the middle of the glass.
2. Pour the syrup slowly over the back of the spoon.
3. Pour the dish soap slowly over the spoon back.
4. Add a drop of food coloring to the water and stir.
5. Pour the colored water slowly over the spoon back.
6. Pour the cooking oil slowly over the spoon back.
7. A grown-up adds the rubbing alcohol last, over the spoon. A grown-up does this
8. Guess which layer each object will stop in, then drop them one by one.
   Ask: Which layer do you think the grape will stop in, and why?
9. Show your friends, or build another tower! What would you change?
   Ask: What new object would you test, and where do you think it will stop?

Play it again

• Mystery order: lay out the liquids and guess the stacking order before pouring.
• Object hunt: test ten new small objects and sort them by which layer they stop in.
• Salty twist: stir salt into the water layer, then see how the objects behave.