======Pepper and Water Surface Tension====== **Materials: **{{$demo.materials_description}}\\ **Difficulty: **{{$demo.difficulty_description}}\\ **Safety: **{{$demo.safety_description}}\\ \\ **Categories:** {{$demo.categories}} \\ **Alternative titles:** Pepper and Soap Surface Tension ====Summary==== {{$demo.summary}} ====Procedure==== -Pour 1–2 cm of water into a shallow dish or plate. -Scatter a light, even layer of black pepper across the water surface. -Gently touch a clean dry finger to the water and note that little changes. -Place a tiny drop of dish soap on a fingertip, cotton bud, or toothpick. -Lightly touch the soapy tip to the center of the water surface and observe the pepper rush outward. -Reapply a trace of soap and touch a new spot if you want to trigger a second motion. ====Links==== Pepper and Water Science Trick! Surface Tension Mini Segment - learningscienceisfun: {{youtube>SS2jBoGwT8s?}}\\ Pepper and Water Science Trick - DaveHax: {{youtube>ho0o7H6dXSU?}}\\ 📄 Pepper and Soap Experiment - Education.com: [[https://www.education.com/activity/article/pepper-and-soap-experiment/]]\\ 📄 A Soapy Magic trick - Discovery Centre: [[https://discoverycentre.thekids.org.au/siteassets/pdfs/germs/2---activity-at-home---a-soapy-magic-trick.pdf]]\\ ====Variations==== *Test different soaps or detergents and compare how strongly they move the pepper. *Try warm versus cold water to see how temperature affects the speed of motion. *Swap pepper for ground cinnamon or paprika to compare particle size and hydrophobicity. *Float a small paper raft, then touch soap behind it to make a simple surface tension boat. ====Safety Precautions==== *Do not put anything from the experiment into your mouth. ====Questions to Consider==== *Why does the pepper float instead of sinking or dissolving? *What property of soap changes the behavior of the water surface? *Why does the motion stop after a short time even if pepper remains on top? *How would using skim milk, whole milk, or salt water change the result, and why?