study the physical characteristics of the gas
history of scientific discovery often begins with the fact that the "right" person in the right place at the right time.This is what happened with the study of gases.French physicist, chemist, engineer Serge Charles became interested in aeronautics.In this regard, it was necessary to study the temperature dependence of the pressure air.Of course, the heat has always been the first tool of researchers.Still, a powerful, easy to control the source of energy and is always at hand.The most ancient instrument of knowledge has always been a touchstone of "well, well, let's see what happens when it is sensitive to heat, and if you add ..." etc.
And what's so interesting found Charles in gases?Do your research.Take a glass tube, on the one hand it will close tightly, and arrange in a piston that glides through the tube.Next to establish the source of heat - the usual alcohol lamp - and equip our laboratory bench gauges of temperature and pressure - in fact the temperature dependence of the pressure we are going to explore.Let's start ...
We have a certain amount of gas in the volume bounded bottomed cylinder and piston.We fix the piston and podogreem alcohol lamp test gas.We write more pressure values Pn and temperature Tn gas.Analyzing the data, we see that the temperature dependence of the pressure is proportional to the character - increases with increasing temperature and pressure.Note that the piston is subjected to pressure in different ways: from the outside - it is atmospheric, and the inside - from the heated gas.For the next experiment remove a clamp piston and see that the piston moves to pressure equalization.But it changed the volume of gas, and the amount (weight) remains the same.We conclude that got Charles: at constant volume and mass of the gas pressure is directly proportional to temperature - simply and tastefully.
In other words, at a constant volume of heating increases pressure and at constant pressure increases the volume when heated.For aeronautics, this meant that when heated air from the burner, it expands and its volume increases, and the volume of a sphere - not.So, once the ball leaves the air and inside the air mass is less than the mass of the same volume of air from outside.Fires Archimedes' principle, and the ball remains nothing how to fly to the delight of the audience.
But the most remarkable finding is that the pressure P and temperature T are related by P1 / T1 = P2 / T2 = .... = Pn / Tn = CONST.It can be interpreted differently: P = k * T, where k - some gas constant.If these relations are applied to the unit values of temperature, pressure, and volume, it is possible to obtain a well known constants.For example, the gas volume increases during the heating of 1 ° to 1/273 of the original value.
definitely more interest is the dependence of the pressure on the temperature of substances during phase transitions, for example, a liquid to a gas.The closest object for studies of this kind is water.Formed over the surface of the water vapor is the consequence of the transition of a certain number of water molecules from the outside environment.This was hindered by two factors - the surface tension and the external pressure.Overcoming them can afford only the molecules with sufficient energy potential - equivalent temperature.There are two ways to achieve this potential: it is possible to increase the energy of the molecules by heating water or reduce resistance to external pressure.The first method is confirmed by the well-known fact - heated water evaporates more quickly, and the second - lowers the threshold energy of the molecules, leaving the "parent" environment.
return to our laboratory setting.The space below the piston is filled with water, very little, just 20-40 g Note that the piston must move freely, and the system should be faulted valve.If the water is heated, the resulting water vapor moves the piston and frees itself "a place under the sun."The space above the piston to be connected to a source of air pressure changes, for example, to install a second manually operated piston rod.Now you can explore the dependence of the temperature of the vapor pressure.By moving the piston and rod, change the appearance of the first piston pressure.Interim data fix.Correctly will record the temperature of steam at a steady, ieunchanged, at least briefly, the meaning.If we neglect the heat exchange with the environment, the behavior of the pair is not very different from the behavior of an ideal gas.
Interestingly, even at such a primitive setting can be observed dependence of the boiling temperature of the pressure.Recall that called boiling transition from liquid to vapor to form bubbles throughout the entire volume of liquid.Thusboil very easy to fix.And there is also increasing pressure to boiling temperature of the liquid increases, and therefore, it is easy for the uninitiated to demonstrate an amazing trick - boiling water at a temperature of only 80 degrees Celsius, or seemingly contrary to common sense, more than 110 of the same degrees Celsius.
So after examining the behavior of a gas, vapor when exposed to heat sources on the matter, in the end, and were created by the different heat engines: the steam engine, portable engine, steam engine, the internal combustion engine.And few know that the first-born among them, of course, should be considered a balloon.
