Question

if you try to hold a glass rod with oil on your hands,it tends to slip. why?

Answer 1

we can hold any object in hand due to frictional force which resist to slip but due oil on your hand decrease frictional force due which glass rod tends to slip

Answer 2

This happens because of the cohesion force. This means that the molecules of the oil and glass are not in a strong bond this whenever you hold a glass tube with oily hands it tends to slip.