00:09Uważam, że samy substancje existuje jak solid, jak liquid, jak gaz, w tym razem.
00:16Wtedy nie ma, by to?
00:18To jest w znamenie jak triple point, a który jest znany nowotny.
00:22Any pure substance can exist in 3 phases.
00:26It can be a solid, a liquid or a gas.
00:29We can show these phases using a pressure-temperature diagram, called a PT-diagram.
00:35This graph shows the location of the different phases of a pure substance in relation to pressure and temperature,
00:42with pressure P on the vertical axis and the temperature T on the horizontal axis.
00:48The three phases are separated from each other by so-called separation lines.
00:53There is a melting line between the solid and the liquid phase,
00:56a sublimation line between the solid and the gaseous phase,
01:00and a vaporization line between the liquid and the gaseous phase.
01:04The triple point is the location where all of these lines meet.
01:08It is specified by a certain pressure and temperature that is characteristic for each substance.
01:15If a pure substance is at least specified temperature and pressure values,
01:20all three phases will be present at the same time.
01:24One says that the three phases coexist.
01:27Pure water has a triple point temperature of 0.01 degrees Celsius
01:32and a triple point pressure of 611.5 Pa.
01:36This is the same as about 0.6% of the usual atmospheric pressure.
01:42At this point water will exist both as ice, as liquid and as vapor.
01:47Let's see what this looks like in practice.
01:50For this experiment we need a vacuum chamber which is connected to a vacuum pump.
01:55A combined pressure and temperature sensor is connected to the hose between chamber and pump.
02:01It is also connected to a PC via USB and values of absolute pressure and temperature in degrees Celsius can be shown on the screen.
02:11Inside the chamber we place a Petri dish with liquid water.
02:16After the chamber has been sealed the pump is switched on.
02:20Both pressure and temperature start decreasing immediately.
02:24During evacuation the liquid water starts to boil as the pressure drops to the saturation pressure at the given temperature.
02:35The glass beads reduce the splashing of water during boiling while the pressure decreases.
02:41They will also provide nucleation sites for the other two phases.
02:45While the pressure drops quite quickly it takes longer for the temperature to approach values around 0.01 degrees Celsius.
02:54Unfortunately our pressure sensor cannot measure below 1.2 kPa but we will see later that the pressure is low enough as the water will be in all three phases.
03:05This can however take a few minutes.
03:08After some time we see both formation of ice on the surface of the liquid water and that vapor bubbles appear in the liquid.
03:17We now have a situation where the water is boiling under a thick layer of ice.
03:23This is water at its triple point.
03:26All three phases coexist.
03:28The different phases are however not in equilibrium as the amount of water in each of the phases changes with time.
03:37When we switch off the pump the water will be stable at a triple point as long as the chamber manages to hold the necessary pressure and temperature conditions.
03:50Once we open the inlet valve and increase the pressure back to normal we can see that the vapor bubbles disappear first.
03:59Small droplets on the glass bell eventually evaporate and the ice in the petri dish begins to melt.
04:06In a second run of the experiment we also place a small beaker with sulfuric acid in the chamber.
04:14The acid attracts water molecules from the gas phase and helps to improve the vacuum.
04:20The steam produced during boiling
04:48podróżu podróżnicą w
04:53całku
04:56klubin jest wiedza
04:59obożne temperatury i
05:01jedna ze seven
05:02bazy units
05:03w jest
05:06podróżnicą
05:08podróżnicą
05:10nie ma
05:11wydanie
05:13podróżnicą
05:13podróżnicą
05:15podróże
05:16to the solid phase.
05:18This process is called deposition.
05:20We can observe this effect in nature.
05:23Fernfrost can form on solid surfaces
05:25by the direct deposition of water molecules
05:27when the surrounding air
05:29is at temperatures below zero degrees Celsius.
05:46Let us know in the comment box below.
05:52If you are not aware,
05:54we can see theàn儿 in the weather itself.
05:58We can see the Forward 100 being in theивает.
06:00The Forward 100 being in the Purple of the Winter
06:03is very Expressing the elevated is the first time
