The source of energy for the Earth is the Sun. Solar energy underlies many phenomena occurring on the surface and in the atmosphere of the planet. Heating, cooling, evaporation, boiling, condensation are some examples of what thermal phenomena occur around us.
No processes in themselves occur. Each of them has its own source and implementation mechanism. Any thermal phenomena in nature are due to the generation of heat from external sources. Not only the Sun can act as such a source - fire also successfully copes with this role.
To further understand what thermal phenomena are, it is necessary to define heat. Heat is the energy characteristic of heat transfer, in other words, of how much energy the body or system gives (receives) when interacting. Quantitatively, it can be characterized by temperature: the higher it is, the more warmth (energy) a given body has.
In the process of interaction of bodies with each other, heat is transferred from a hot to a cold body, i.e., from a body with a higher energy to a body with a lower energy. This process is called heat transfer. As an example, consider boiling water poured into a glass. After a while, the glass will become hot, i.e., there has been a process of heat transfer from hot water to the cold glass.
However, thermal phenomena are characterized not only by heat transfer, but also by such a concept as thermal conductivity. What it means can be illustrated by an example. If you put the pan on the fire, then its handle, although it does not touch the fire, will heat up just like the rest of the pan. Such heating is provided by thermal conductivity. Heating is carried out in one place, and then the whole body is heated. Or does not heat up - it depends on what heat conductivity it possesses. If the thermal conductivity of the body is high, then heat is easily transferred from one section to another, but if the thermal conductivity is low, then heat transfer does not occur.
Before the concept of heat appeared, physics explained thermal phenomena using the concept of “heat”. It was believed that each substance has a certain substance, similar to a liquid that performs a task that, in modern terms, solves heat. But they rejected the idea of the calorific after the concept of heat was formulated.
Now we can examine in more detail the practical application of the previously introduced definitions. Thus, thermal conductivity provides heat transfer between bodies and within the material itself. High values of thermal conductivity are characteristic of metals. For dishes, a teapot, this is good, because it allows heat to be supplied to the prepared products. However, materials with low thermal conductivity also find their application. They act as heat insulators, preventing heat loss - for example, during construction. Thanks to the use of materials with low thermal conductivity, comfortable living conditions in houses are provided.
However, heat transfer is not limited to the above methods. There is still the possibility of heat transfer without direct contact of the bodies. As an example, warm air flows from a heater or radiator of a heating system in an apartment. A heated object (heater, radiator) emits a stream of warm air, heating the room. A similar method of heat exchange is called convection. In this case, heat transfer is carried out by flows of liquid or gas.
If we recall that the thermal phenomena occurring on the Earth are associated with the radiation of the Sun, then there is another way of heat transfer - thermal radiation. It is due to the electromagnetic radiation of a heated body. That is how the sun heats the earth.
In the given material, various thermal phenomena are considered, the source of their occurrence and the mechanisms due to which they occur are described. The issues of the practical use of thermal phenomena in everyday practice are considered.