How Water Beats Rock

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Author: Angela Pike

Grade Level: 1st - 5th; Type: Earth Science


Build a model to explore how water and ice can change the form of rocks. 

Research Questions:

  • What is weathering?
  • How can water, frozen and unfrozen, change rocks?
  • When water freezes in a rock, why does it crack?

Rocks are ever changing. They can be smoothed by water, broken off by wind, and cracked by ice. If you found a rock in your backyard then traveled back in time 1,000 years, that rock would look totally different because of changes that have occurred to it. One way that rocks change is when water gets into small cracks and then freezes.  When the water freezes, it expands thus causing the rock to crack and even sometimes bust open.  


  • Water
  • Wax paper
  • Dough mixture
  • Small balloon
  • Freezer

Experimental Procedure:

  1. Carefully fill the balloon with water until it is the size of a golf ball. Try to get all air out of the balloon before tying it closed.
  2. Spread out a piece of wax paper on the table. Use your hand to flatten out a 2 inch ball of dough until it is about ¼ inch thick. 
  3. Place your balloon of water on top of the dough and carefully wrap the dough around the balloon. Smooth the dough around the balloon so there are no cracks and that none of the balloon shows through.
  4. Leave your dough-covered balloon on the wax paper for 2-3 days to harden. Think of this hardened ball as a “rock.” Once it is dry, place it in the freezer overnight.
  5. The next day, observe your “rock.” What happened to it? What did the water inside the balloon do? 

Terms/Concepts: Weathering; Erosion; Rocks; Ice




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