======Water on a Coin======


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**Alternative titles:** Drops on a Penny
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====Summary====                   
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====Procedure====  
  - Place a clean coin on a flat surface.  
  - Use an eyedropper to carefully place drops of water on the coin, one at a time, while counting.  
  - Continue until the droplet spills over, then record the number of drops.  
  - Wipe off the coin or use a new one.  
  - Repeat the process using oil or corn syrup instead of water, comparing the number of drops each liquid can hold.



====Links==== 
Drops of water on penny - Kids Fun Science: 
{{youtube>G7mc05yyU0M?}}\\


📄 Science World - Drops on a Coin: [[https://www.scienceworld.ca/resource/drops-penny/]]\\

====Variations====
  * Add a drop of soap to the water to see how reduced surface tension changes the number of drops.  
  * Try using coins of different sizes (pennies, nickels, dimes) to compare results.  
  * Perform the same experiment by adding coins one by one into a full glass of water to see how surface tension allows the water to rise above the rim.



====Safety Precautions====
  * Clean up spills promptly to avoid sticky surfaces from syrup or oil.  
  * Use only clean coins and avoid putting them in your mouth.  
  * Dispose of used liquids properly—do not drink them.




====Questions to Consider====
  * How many drops of water fit on the coin compared to your prediction?  
  * Why can more drops of water fit on a coin than drops of oil or syrup? (Because water’s cohesive hydrogen bonds create stronger surface tension than nonpolar liquids.)  
  * What causes the "skin" on the surface of the water droplet? (Surface tension from cohesive forces between water molecules.)  
  * Would a larger coin hold more drops of water? Why or why not? (Yes, because of a larger surface area, but size is more important than coin value.)  
  * What effect does soap have on the number of drops that fit? (Soap disrupts hydrogen bonds, lowering surface tension, so fewer drops fit.)