The thermal expansion

In general, matter expands when the temperature increases, and it contracts when the temperature decreases. Even liquids expand as temperature increases. For example, liquids contained in thermometers (such as mercury and ethyl alcohol) increase their volume when their temperature increases. The expansion that matter undergoes mainly occurs in the direction of length the so called linear coefficient of thermal expansion. The change along length of a substance when its temperature increases by Dt is: 1.Directly proportional to the initial length of the object 2.Directly proportional to the temperature variation undergone by the substance 3.It depends on the substance of the object. These properties can be summarized in the law of linear expansion the Δl = λ l_o Δt