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Q: (i)there are large amount of gas molecules in a small volume (ii)the range of intermolecular force(att & rep) is small compared with the av. distance between molecules.
The 1st assumption, you should have learnt that in the derivation of pressure, we assume that at any time instant, there are equal number of molecules moving in each direction (i.e. x, y bad z directions). If the number of molecules is small, such assumptions may not be valid.
The 2nd assumption, if the average separation between molecules is comparable to the range of intermolcular force, the motion of molecules would be influenced by the force, and molecules would not be moving in a straight line. Since in kinetic theory we assume molecules are moving from one side of the container to the other side in a straight line, the molecular separations thus have to be large compared with the range of intermolecular force.
Q: 同埋想問點解做exp 要prove charles's law係岩既..戈陣要係支capillary tube到加mercury thread 就可以keep pressure constant???咩原理???
I don't know what apparatus you used. I suppose the mercury is placed in a U-tube such that by adding mercury into one side of the U-tube, the mercury tended to equalize the pressure between the two arms of the tube. As such, the pessure on the other side of the tube would increase.
Q: 同埋5加mercury 又點???
Charles Law states that the volume of a fixed mass of a gas is porortional to its absolute temperature, provided that the pressure is kept constant.
Hence, if the temperature of a gas is raised, both its volume and pressure increase. Should the pressure not be kept constant, you could not prove Charles Law. Adding mercury is a step to keep the pressure of the gas remains unchanged.
