Here's why:

* Chemical Reactions: Bases react with acids to form salts and water. This reaction is called neutralization.

* Hydroxide Ions: Bases typically contain hydroxide ions (OH-) in solution.

* Slipperiness: These hydroxide ions interact with the molecules of your skin, causing a slippery feeling.

Important Note: While slipperiness is a common characteristic, it's not the *only* physical property of bases. Other physical properties can include:

* Taste: Bases generally taste bitter (though you should never taste a base to test for it).

* Color: Some bases can change the color of certain indicators, like litmus paper.

* State: Bases can exist as solids, liquids, or gases.

Let me know if you have any other questions!