If a glass of boiling water leave the cold spoon, then after a while the temperature of the temperature of the water.Water cools down a bit, and spoon, on the contrary, is heated.The temperature at which it becomes the same and comes into equilibrium, a certain amount of heat transferred from the hotter to the colder body.
From the point of view of modern molecular-kinetic theory of the subject with a high temperature there was a transition of power to the subject with a low temperature.And this transition takes place, until the temperature equals two bodies, iethey will come to a state of thermal equilibrium.In fact, the concept of the quantity of heat, which is a measure of energy transfer, preserved since when physicists use a term such as caloric.
However, this does not mean that today we can not be guided.This concept is quite accurately describes the processes occurring during the heat exchange.It is generally the amount of heat by the letter Q and is measured in joules.Or are obsolete units - calories and (larger) calories.Now, perhaps, you have a little touch that will occur with the substance in the preparation of any external energy.
When heat transfer received energy (heat) can be spent on heating the substance or object (a teaspoon in a glass), changing its state of aggregation - melting (butter in a skillet) or evaporation (kettle on the stove).Clearly, this is a different process, and each of the described phenomena need your energy.Scientists have finally found possible to carry out calculation of the amount of heat required in each particular case.
However, here too, it was not so easy.In that case the aggregate state of the substance does not change, the resulting energy is proportional to the body weight and the temperature difference between the interacting bodies.It should be understood by the following example.If a glass of boiling water put a spoonful of light, then spoon heats up quickly, and if a light glass of boiling water put on a massive metal plate, the change in temperature of the plate can be detected only by using special devices.
The described dependencies are not taken into account another factor - the properties of the substance itself.To describe the characteristics of the material using a special option - the so-called specific heat.This value indicates the amount of heat which is necessary to transfer the substance to change its temperature by 1 ° C.Each material, this quantity characterizing the ability to make (give) the heat own.
If in the process of heat transfer changes the state of the body, i.e.it melts and turns into steam, then talk a little bit about the other things.For melting substance fed to it the amount of heat called heat of fusion, and the vapor - heat of vaporization.
Thus, instead of the specific heat is used in calculating the specific heat of melting or evaporation.Due to these factors can be found the amount of heat required to melt or vapor transfers the desired amount of substance.To do this, you only need to multiply the ratio of the specific heat of melting or evaporation on the weight of the substance.That will have the desired amount of heat to produce the desired result (melting or evaporation).These ratios can be easily found in the manuals.
That's how you can describe what the concept of the quantity of heat with which it is associated, on what is spent, and how to identify and calculate the generated (absorbed) heat at different physical processes.
