Sink the Egg Challenge

Now is the time of year when plastic eggs become widely available in stores, and they also reemerge from under beds, the back of the closet or the top shelf of the garage. In some households, these eggs are filled with treats by adults, and hidden for children to find. Other households hide the eggs outside multiple times and decide who can find the most. This year I found a STEM challenge that can be done indoors, with less risk of losing the eggs. 

This challenge is about guessing (or hypothesizing) whether the item you place in the plastic egg will make the egg sink.  

For this game, you will need the following supplies: 

  • Plastic eggs 
  • Water
  • Container to hold water (mixing bowl, sink, bucket)
  • Assorted items that fit into an egg (see ideas below)
  • Optional: paper and pencil

I suggest having your items for inside the eggs preselected and ready before you and your child begin experimenting. I organized my items in a muffin tin. If your eggs have holes, cover those with tape to make water-tight seal.

First, have your child drop an empty egg into the water and observe how it floats. They may want to push on it to test its buoyancy. Then investigate the items to go inside the eggs. Which ones do they think will make the eggs sink? Will it take more than one? 

Here is where you can adapt the game for different age levels. Younger children may enjoy sorting items by what they think will float and what will sink. Older children can make a list of the items, write their hypotheses and the later results. 

When ready, place an item into an egg and drop it into the water. Is the egg floating? Are you surprised by the result? With smaller items, you can further experiment by seeing how many you can fit into the egg and how many it takes to make the egg sink. 

Here are possible items for inside the eggs:

  • Metal screws
  • Pom-poms or cotton balls
  • Coins
  • Rocks
  • Small toys
  • Toy jewelry
  • Dice
  • Snacks or candy
  • LEGO
  • Broken crayons
  • Hair accessories
  • Binder clips or chip clips

The idea of this challenge from a blog on