You must have seen an oil lamp  before. But do you know how it works?  One end of the lamp wick  is immersed(............) in oil and the other end is not immersed. When you light the end which is not immersed, it  will burst into flame . This is because the oil is able to rise up the lamp wick thus helping it to burn.     In the same way, if you immerse the end of a piece of chalk into a glass of water, the water will soon climb up the chalk making it wet. If a piece of ordinary glass tubing is heated in a gas flame until it becomes soft,it can be pull into a tube of a very small hole. Immerse the tube into water or any other liquid which wets glass, you will find that the liquid rises to a height of several centimeters. This is known as capillary action. The liquid rises because there is an attractive force between the liquid and the glass. The attractive force depends on the diameter of the tube and the type of liquid used. Why can an oil lamp work?
Because there is oil. Because there is oil climbing up the wick. Because the other end is immersed. Because the wet end is lighted.