======Freeze Thaw Weathering======


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**Alternative titles:** Ice Wedging Demonstration
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====Summary====                   
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====Procedure====  
  - Snap a piece of pavement chalk in half to create fresh surfaces.  
  - Submerge the chalk in cold water and keep it there until no more air bubbles escape (gently move it to release trapped air); the pores should be filled with water.  
  - Remove the saturated chalk, place it in a plastic bag (to contain fragments), and put it in a freezer for at least 6 hours or until fully frozen.  
  - Prepare a bowl of hot water. Using tongs, transfer the frozen chalk into the hot water and observe any cracking or flaking.  
  - Re-soak the chalk in cold water to refill pores, then repeat the freeze (bag → freezer) and warm steps.  
  - Continue cycling freeze → warm → re-soak until the chalk fractures; record how many cycles are needed and what type of breakage occurs (cracks, flakes, shattering).



====Links==== 
Physical Weathering: Freezing - AusEarthEd: 
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📄 Freeze-Thaw Weathering - Fizzics Education: [[https://www.fizzicseducation.com.au/150-science-experiments/geology-rocks/freeze-thaw-weathering/?srsltid=AfmBOoo-PtjZqntUEKxvsQ8vZko50QmE0KVJtrGj9Zu9PRgDL-ozv1zp]]\\


====Variations====
  * Compare small chalk pieces versus larger chalk blocks and note cycle counts to failure.  
  * Test different warming methods (room temperature vs hot water) to see how thermal change affects cracking.  
  * Try partially saturated chalk (short soak) versus fully saturated chalk (long soak) to assess the role of pore water.  
  * Place chalk on a rough surface while warming to mimic abrasion from moving fragments.  
  * Advanced: Use dry ice for the cooling step and boiling water for warming to increase thermal stress (only with strict supervision and added safety precautions).



====Safety Precautions====
  * Use tongs when handling hot water and frozen chalk to avoid burns and cold injury.  
  * If using an oven or very hot water, heat-resistant gloves are required; keep water below boiling unless specifically testing that variable.  
  * Contain the sample in a plastic bag during freezing to prevent loose shards; open the bag away from the face when removing chalk.  
  * Keep work area dry to prevent slips; wipe up spills promptly.  
  * Advanced variation with dry ice: adult supervision only; wear insulated gloves; work in a well-ventilated area; never seal dry ice in an airtight container.




====Questions to Consider====
  * Why is the chalk soaked before freezing? (Filling pores with water allows expansion upon freezing to generate stress.)  
  * What causes the chalk to crack during freezing? (Water expands about 9% when it freezes and ice crystal growth exerts pressure on pore walls.)  
  * How does repeating the freeze–thaw cycle change the result? (Microcracks accumulate and link up, weakening the material until it fails.)  
  * Which rocks in nature are most susceptible to freeze–thaw weathering? (Porous or fractured rocks such as sandstone and limestone; fine cracks in granite can also widen.)  
  * Where on Earth would this process be most active? (Mountainous or temperate regions that cross 0°C frequently, where water can infiltrate and freeze.)  
  * How does this model differ from real-world rockfalls and pothole formation? (Real rocks experience additional stresses like pressure release, salt crystallization, and abrasion, but freeze–thaw is a major contributor.)