Why does soap wash off greasy hands but water alone just rolls off the grease?
Washing greasy hands after eating pizza or fries (or dish soap cutting a greasy pan after dinner) - something a kid does every day; bath-time bubbles is a secondary hook.
Talk about it
- Predict first: if you rinse a greasy plate with plain water, where does the grease go?
- Each soap molecule has a tail that loves grease and a head that loves water. Why would needing both ends make it such a good cleaner?
- We washed grease off with soap. What is a mess that plain water can wash away all by itself?