In physical terms, we say that the temperature of a body (or object) is a measure of the agitation of the atoms and molecules that make it up. Therefore, we can say that the higher the temperature of a body, the greater the agitation of its atoms or molecules. The increase in the temperature of a body not only causes an increase in the agitation of atoms and molecules, but also causes other effects in the body.
Thus, all bodies that are in nature are likely to suffer some effect due to the increase in their temperature. In some bodies, these effects may be visible, but not in others. When there is an increase in the temperature of an object, it also suffers an increase in its dimensions, so the objects dilate.
We define the dilation as the variation in the dimensions of an object due to the variation in temperature. Therefore, we can say that dilation is a macroscopic manifestation of the variation in the kinetic energy of molecules and atoms.
Almost all materials existing in nature suffer an increase in volume when their temperature rises, as a result, the density of these objects decreases. It can be said that this rule is valid for almost all substances. An exception is water that behaves differently when its temperature varies from 0ºC to 4ºC. This phenomenon is known as the anomalous state of water.
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The increase in temperature generates an increase in the separation between the atoms or molecules of a substance that causes a change in volume
The figure above allows us to better understand how the expansion of materials occurs with increasing temperature. We can see that in the first situation, at a certain temperature, the atoms and molecules of the substance vibrate around an equilibrium position. For this temperature value, the average distance between the molecules is practically constant.
However, when there is an increase in the temperature of the substance, the molecules or atoms start to vibrate more rapidly, that is, they vibrate with greater amplitude, consequently, they are a little more distant from one of the others. This greater separation, that is, this greater distance between atoms and molecules, is reflected in the increase in the object's dimensions.
We can conclude by saying that the effects caused by thermal expansion are of paramount importance when designing machines that use different types of parts of different materials, which are in contact with each other, because with the variation of temperature, these parts will expand in a way different.
By Domitiano Marques
Graduated in Physics
Would you like to reference this text in a school or academic work? Look:
SILVA, Domitiano Correa Marques da. "Dilation – a property of materials"; Brazil School. Available in: https://brasilescola.uol.com.br/fisica/dilatacao-uma-propriedade-dos-materiais.htm. Accessed on June 27, 2021.
