Thermal expansion is nothing more than the increase in body dimensions caused by the increase in temperature. The expansion takes place in almost all materials, whether in solid, liquid or gaseous state. For an object in its solid state, it may undergo linear dilation, which consists of an increase in only one dimension, surface dilation, which it consists of an increase in two dimensions of the object and, finally, it may undergo volumetric expansion, which consists of an increase in the three dimensions of the object.
Like solids, liquids can also expand. We cannot study a liquid without putting it in a container, and containers also increase in volume when their temperature increases. What is known is that the container almost always undergoes less expansion than a liquid.
The volume of an object varies with temperature according to the following expression:
∆V=γ.V0.∆T
In the equation above, we have that γ (gamma) represents the volumetric expansion coefficient. A simple way to determine the value of the coefficient of volumetric expansion of liquids is to place it in a container and measure the volume at two different temperatures. After measuring the volume for two different temperatures, simply use the equation below to determine the coefficient.
From the above equation, we isolated the volumetric expansion coefficient as follows:
In the equation above, we have to ΔV and ΔT represent the variations in volume and temperature suffered by the liquid. We determine the volume occupied by the liquid by measuring its level inside the container. However, when we measure the volume of the liquid, we are measuring the apparent volume, as the container also expands, therefore, its volume varies.
To determine the actual volume variation it is necessary to reduce the volume variation that the container undergoes. For this, it is necessary to know the volumetric expansion coefficient of the container. The actual variation in the volume of the liquid is greater than the initial measurement obtained, looking at the increase in the level of the liquid in the container.
It can be concluded, then, that all liquids increase in volume when the temperature increases.
By Domitiano Marques
Graduated in Physics
Source: Brazil School - https://brasilescola.uol.com.br/fisica/dilatacao-real-ou-aparente.htm