Step-by-step tutorial
Step 1
Gather your materials.
Step 2
Use the funnel to fill one bottle with foam pearls.
Step 3
Fill the other bottle with water.
Step 4
Cover the top of the water bottle with anything thin and flat.
Step 5
While keeping the top covered, flip the bottle over and align it on top of the bottle filled with pearls.
Step 6
Remove the cover.
Step 7
Remove the cover and watch as the pearls rush into the top bottle.
Step 8
Reverse Hourglass
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Learn more
This activity is all about buoyancy and density! Density measures how tightly stuff is packed inside an object. Water is heavy and dense, while the tiny foam pearls are filled with air pockets, making them much lighter than water. When you connect the bottles, heavy water rushes down into the bottom bottle because gravity pulls harder on denser materials. As the water fills the bottom bottle, it pushes the lightweight foam pearls out of the way, sending them floating upward like an upside-down hourglass! If you don’t mind getting a little wet, this is an activity you can repeat over and over just by flipping the bottles back around.
