點解 "helium" 係一種咁特別既 atom !!!!

其實如果係change of state 係同佢個 physical property事...一物質如果要改變佢個state,其實係同佢的atom的"密度"有關,而要令atom排得密d
1)降低溫度→動能 decrease(atom 震的幅度減少)→排得密d
2)加大壓力→atom 震的幅度減少→排得密d
因為helium 個原子核好細,所以要好低溫先可以令helium atom 的動能降低到可以變成液體
K.E=1/2m(v)square.你俾好少能量粒helium atom 佢就會有好大的 velocity.so 要好大的壓力先可以令減低個velocity...so 1atm 係唔夠的....

Since helium has only 1 electron shell, when 2 helium get close together, there is great repulsion between thier nucleus. Thus, a lot of energy needed to be provided to force them get even closer (changing of physical state). I think you can think this way also