The thermal contraction It is a physical phenomenon due to which matter, whether in a solid, liquid or gaseous state, loses a percentage of its metric dimensions as its temperature is removed. For example: the liquefied gases, thermal erosion, uncovering jars.
In that sense, it is opposite to the thermal expansioncharacterized by the increase in proportions due to the energetic increase in the atoms of matter as a result of the increase in temperature.
Both phenomena are due to the effect that the injection or withdrawal of caloric energy has on the particles of matter, since it makes their atoms vibrate at a higher or lower rate, respectively, thus requiring more or less space for movement.
This phenomenon is perfectly observable in gases, for example, whose volume responds to temperature, expanding and volatilizing when hot, and contracting and even liquefying when cold.
These types of phenomena are of vital importance in the architectural and construction industries, since the choice of materials in light of climatic conditions may very well represent a problem with regard to the stability of buildings.
Lastly, it should be noted that not all materials respond in the same way to expansion and contraction processes, and some even respond to only one of the two. For example, water expands when brought below 4 °C.
Examples of Thermal Shrinkage
- uncover jars. A known technique for uncovering jars with metal lids is to expand them using heat, since having spent a long time in the fridge or freezer, the metal contracts and it is much more difficult to turn it.
- The gas liquefied. By cooling a gas to a certain point, a thermal contraction is induced such that its particles can change the structural arrangement between them and thus become a liquid. This process is known as liquefying and is usually also produced through variations in pressure, forcing the particles to contract through the environmental force.
- Freezing of the water. Water expands noticeably when it approaches its boiling point (100 °C), and contracts when it drops to 4 °C, acquiring its point of greatest density (greater proximity between its particles). Once below that temperature, it expands slightly again as it becomes a solid.
- thermal erosion. Exposure to the increase in temperature during the day and the decrease at night, in cases of very high thermal variability, lead to the erosion of rocks and solid materials in the environment, which expand during the day and contract at night, thus favoring the loss of its usual density.
- Cold shrink assembly. In many manufacturing industries, complex pieces of machinery (flanges, pipes, lever pieces) are assembled from their hot assembly, when they are expanded, since later, when they cool down, the pieces will contract and remain firmly in place.
- ceramic tiles. Ceramic for domestic use is very susceptible to expansion and contraction, and for this reason it is usually surrounded by an elastic application when fixing it in place, to keep it pressed in cases of contraction and cushioned in cases of expansion.
- thermometers. Being a metal and also a liquid, mercury responds very well to thermal expansion, expanding when hot and contracting when cold, thus making it possible to show changes in temperature.
- the roofs of the houses. During the winter, construction materials tend to contract, causing deformations similar to those of their expansion during the summer. This is also due to the characteristic sound of wooden houses when this material cools and contracts at night.
- heat shock. Subjecting certain materials that are highly expanded by the action of heat to a sudden loss of temperature (a bucket of water, for example), will cause their rapid and violent contraction, thus generating cracks or fissures in the material.
- glass handling. The famous experiment of how to put a whole boiled egg in a glass bottle is based on this principle. The glass is heated to expand it until the egg can pass through the mouth, and then it is cooled to contract it and recover its original dimensions.
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