Volumetric Expansion
In general, objects expand in all directions as temperature increases. In these drawings, the original boundaries of the objects are shown with solid lines, and the expanded boundaries with dashed lines. (a) Area increases because both length and width increase. The area of a circular plug also increases. (b) If the plug is removed, the hole it leaves becomes larger with increasing temperature, just as if the expanding plug were still in place. (c) Volume also increases, because all three dimensions increase.
Source
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"OpenStax College, Thermal Expansion of Solids and Liquids. February 2, 2013."
http://cnx.org/content/m42215/latest/
OpenStax CNX
CC BY 3.0.