It’s important to always wash your hands with soap and warm water for at least 20 seconds when your hands are dirty. It is especially important to make sure you have a good hand washing routine during the covid-19 pandemic to help prevent the spread of the virus. Sometimes, though, it feels like your hands get just as clean after washing them with just water instead of soap and water. This experiment helps explain why soap is so important!
What you need:
- A bowl
- Water
- Pepper flakes
- Dish soap
Steps:
- Fill your bowl with water.
- Add the pepper flakes to the surface of the water. These will represent your germs.
- Dip your finger into the bowl and pull it out. Did your finger get any “germs” on it? Probably!
- Clean the pepper off of your finger and coat it in dish soap.
- Stick this finger into the bowl. Watch as all of the “germs” rush to the sides of the bowl to get away from your soapy finger.
- Did you finger get any germs on it this time? Hopefully not!
How does your finger chase off the “germs”?
When you first pour the pepper flakes into the water, most of them float due to surface tension on the water. Surface tension is caused by the attraction of water molecules to other water molecules, or cohesion. When you stick your soapy finger in the water, the pepper flakes rush over to the sides of the bowl because surface tension has been broken by the dish soap. The water molecules want to continue to have surface tension, so they quickly pull away from the soap and to the edges of the bowl, carrying the pepper with them.