======Hydrophobic Coatings======


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**Alternative titles:** Water-Repellent Surfaces
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====Summary====                   
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====Procedure====  
DIY Sand Method:  
  - Spread colored sand evenly in a plate or shallow container.  
  - Spray the sand with a water-repellent fabric protector, coating it thoroughly.  
  - Allow the sand to dry completely.  
  - Place some of the coated sand in a clear plastic cup.  
  - Add water slowly and observe how the sand clumps together instead of mixing with the water.  

Wax-on-Paper Method:  
  - Draw a thick patch with a wax crayon on a sheet of paper.  
  - Drip water onto both the waxed area and the plain paper.  
  - Observe how water beads up on the waxed surface but soaks into the plain paper.



====Links==== 
The science of superhydrophobic surfaces - Imagination Station Toledo: 
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Science Max | Entire Outfit in HYDROPHOBIC Coating | SCIENCE - Science Max - 9 Story: 
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====Variations====
  * Compare treated sand with untreated sand in water.  
  * Use different hydrophobic sprays on various fabrics or paper and test their effectiveness.  
  * Try dripping colored water to make the beading more visible.



====Safety Precautions====
  * Perform spraying in a well-ventilated area or outdoors.  
  * Do not inhale spray mist.  
  * Wear safety goggles and gloves if handling sprays.  
  * Wash hands thoroughly after the activity.




====Questions to Consider====
  * Why does water bead up on hydrophobic surfaces? (Because water molecules stick together more strongly than to the coated surface, due to surface tension.)  
  * How is wax similar to commercial hydrophobic sprays? (Both repel water because they are nonpolar and hydrophobic.)  
  * Where are hydrophobic coatings used in everyday life? (Rain jackets, tents, car windshields, stain-resistant fabrics.)  
  * How does surface tension contribute to this demonstration? (It helps water form droplets that roll off rather than spreading out.)