Mechanical balance means that there is no movement of separate parts of gas. For this purpose it is necessary that gas pressure in all its parts was identical if to neglect the insignificant difference of pressure in the top and lower gas layers arising by gravity.
As we know, the volume of gas is directly proportional to the temperature if pressure remains to constants. Therefore, gas density with an invariable pressure is inversely proportional to absolute temperature. If — gas density at temperatures and, the ratio takes place
Applying these data on the drawing in the form of points, abscissae are values of V, and ordinates — the corresponding values P, will receive a curve — the schedule of process in gas (drawing.
Let's neglect insignificant increase in volume of a flask when heating and minor change of volume at shift of mercury in a narrow manometrical tube. Thus, it is possible to consider gas volume invariable. "water in the vessel surrounding a flask we will note gas temperature on the thermometer, and the corresponding — on the manometer. Having filled a vessel thawing, ice, we will measure pressure corresponding to temperature of 0 °C.
If we knew how air temperature in a vessel changed in our experience, and precisely measured as volume Gaza changes, we could study this phenomenon from the quantitative party. that for this purpose it is necessary to conclude a vessel in a cover, about that all parts of the device had the same temperature, precisely to measure the volume of the locked mass of gas, then to change this temperature and to measure a gas volume.
The size a showing by what part of pressure at 0 °C increases gas pressure when heating on 1 °, has the same value (more precisely, nearly one and that for all gases, namely. Size a call thermal, pressure coefficient. Thus, the thermal coefficient of pressure for all gases has the same value equal.
The thermal capacity with a constant pressure of Cp is more, than a thermal capacity at the constant volume of Cv. Really, when heating 1 g of gas on 1 ° at the constant volume the brought warmth goes only on increase in internal energy of gas. For heating on 1 ° the same mass of gas with a pressure it is necessary to tell him warmly at the expense of which not only internal energy of gas will increase, but also the work connected with gas expansion will be made. For receiving Sp to the size Cv it is necessary to add still the warmth equivalent to the work made at a gas.
So, the absolute temperature of gas is proportional to average kinetic energy of molecules of gas. As average energy of molecules is proportional to a square of velocity of the molecules, our comparison leads to a conclusion that the absolute temperature of gas of a to a square of average velocity of the molecules of gas and that the of molecules grows in proportion to a root square of absolute temperature.
Let's place in a flask a piece of the which is chemically connecting from air (for example, phosphorus), and we will quickly close a flask a stopper from the. attached to a mercury. After a while all oxygen of air with phosphorus. We will see that the manometer will show smaller pressure, than before removal of oxygen. Means, presence of oxygen at air its pressure.
where e — average energy of one molecule. Let's designate gas pressure at temperatures of T1 and T2 letters r1 and r2 and averages energy of molecules at these temperatures of e1 and e In that case
having designated numbers of molecules of the first and second gases, in volume of V, the letters N1 and N2, we can write that the lump of gas is equal to the mass of one its molecule, on number of molecules: M1=t1n1 and M2=t2n2 therefore
When we deal not with gas, and with firm go a liquid, at our disposal there are no such direct methods of determination of velocity of the molecules of a body. However and in these cases it is undoubted that with temperature increase the of motion of the molecules increases.
The number of molecules in one mole of a substance which received numbers of Avogadro is important physical. For definition of number of Avogadro and various researches were made. They treat Brownian motion, the phenomena of electrolysis and some other. These researches led to quite concordant results. Now accept that Avogadro's number is equal