Thermal expansion
All bodies existing in nature, solid, liquid or gaseous, when in the process of heating or cooling, are subject to thermal expansion or contraction.
The process of contraction and dilation of bodies occurs due to the increase or decrease in the degree of agitation of the molecules that make up the bodies. When heating a body, for example, there will be an increase in the distance between its molecules as a result of the increase in their degree of agitation. This greater spacing between them is manifested through the scantion of body dimensions, which can occur in three ways: linear, superficial and volumetric. The opposite occurs when bodies are cooled. When this happens, the distances between the molecules are reduced and, as a result, there is a reduction in the dimensions of the body.
Linear Dilation:it is the dilation that is characterized by the variation in the length of the body. This variation can be calculated from the following mathematical equation:
ΔL = α.L0.ΔT
α: is the coefficient of linear thermal expansion, whose unit is °C-1, which depends on the nature of the material that makes up the body;
Lo: is the initial length of the body;
L and ΔT: are, respectively, the variation in body length and temperature.
Superficial Dilation: it is the dilation that is characterized by the variation in the surface area of the body. This variation in body surface can be calculated using the following expression:
ΔS = β.S0.ΔT
β: it is the coefficient of superficial thermal expansion, whose unit is the same as the coefficient of linear thermal expansion and also depends on the nature of the material that constitutes the body;
β: 2α;
Only: is the initial surface area of the body;
S and ΔT: are, respectively, the variation in surface area and the variation in body temperature.
Volumetric Dilation: it is the dilation that is characterized by the variation in the body's volume. This variation can be calculated with the expression:
ΔV = γ.V0.ΔT
γ: is the volumetric thermal expansion coefficient, whose unit is the same as the linear and surface expansion coefficient and also depends on the nature of the material that makes up the body;
γ: 3α;
Grandma: is the initial volume of the body;
ΔV and ΔT: are, respectively, the variation in volume and the variation in body temperature.
Calorimetry
It's the branch of Physics which studies the energy exchanges between bodies and/or systems when these exchanges occur in the form of heat.
Heat:is the thermal energy in transit, which is determined by the temperature difference between the bodies and/or systems involved.
Temperature: it is the quantity that measures the degree of agitation of the molecules that make up the body.
The general equation of calorimetry is determined by the following mathematical equation:
Q = m. ç. ΔT
ç: is the specific heat of the material;
ΔT: is the variation in body temperature;
Q: is the amount of heat, which has the unit of joule (J).
O heat it can propagate from one body to another in three ways: conduction, convection and irradiation.
Driving: it is the transfer of energy that occurs from molecule to molecule due to their agitation, when subjected to an increase in temperature.
Convection: it is the heat transfer process that occurs due to the fluids, due to the differences in density between the parts that make up the system.
Irradiation: it is the type of energy transmission that takes place between two systems without physical contact between them. This transmission takes place through electromagnetic waves, such as the sun's rays that heat the Earth every day.
By Marco Aurélio da Silva
Source: Brazil School - https://brasilescola.uol.com.br/fisica/dilatacao-termica-calorimetria.htm