Library Blog

Dish Soap Science

colors swirling in water

Here are two super easy science experiments you can do today, using the stuff you already have at home.   

Dish soap and pepper 

Materials: bowl, pepper, dish soap, and a Q-tip (or you can even use your fingertip) 

Step 1:  Fill a light-colored bowl with water   

Step 2:  Sprinkle pepper over the surface of the water.  Do not mix. 

Step 3:  Dip a dry clean Q-tip into the water in center of the dish.  What happens? 

Step 4 Take the dry side of the Q-tip and dip it in dish soap.  Now dip that end it into the water at the center of the bowl.  Watch what happens.    

How it works:   Pepper does not dissolve in water like salt does, but it floats on top of the water because of surface tensionWhen you put the dry Q-tip in the water it only breaks the surface tension at that point.  Soap decreases surface tension.  When we add soap into the water, the water floats away from the soap to keep the surface tension up and takes the floating pepper along with it.  Soap allows dirt and oil to separate from dishes, which makes it a great household helper! 


Dish soap and milk 

Materials: bowl, milk, food coloring, Q-tip 

Step 1:  Fill a light-colored bowl with milk   

Step 2:  Squirt drops of different colored food coloring around the milk.  Do not mix.   

Step 3:  Dip a Q-tip or tooth pick in dish soap.  Now dip it into the water at the center of the bowl.  Watch what happens.   

How it works:   At first, the food coloring just floats.  When the soap is added, it lowers the surface tension and the food coloring flows around the surface of the milk.  Soap also breaks up the fat molecules in the milk which further moves the food coloring around.  Dish soap helps clean our dishes by breaking down grease molecules.   


Both Experiments, Scared Pepper and Milk Art, can be found in Junk Drawer Chemistry: 50 Awesome Experiments That Don’t Cost a Thing by Bobby Mercer.   

Want more fun ideas?  Check out other science project books on our catalog, or on our OverDrive and Hoopla apps.