Helium can be liquefy through a very
low temperature because of the weakness of attractions between the helium
atoms. In addition, helium is a noble gas that has a very weak interatomic London
dispersion forces. Thus, this element would remain liquid at atmospheric pressure
all the way to its liquefaction point going to absolute zero.
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D. the student's conclusion shows experimental bias
Difference between Gas and Vapour:
Gas:
A thermodynamic state in which a substance exists only in one phase i.e. Gas phase. In above given examples N₂, He and CO₂ exists as gases at room temperature. These gases cannot form a solid or liquid phase along with gas phase as these states requires very low temperatures.
Vapours:
It is a thermodyanamic state in which a substance exists in more than one phase. In given options Sulfur can exist in vapor state. This is because sulfur exists in a cyclic or chain form due to catenation (self linkage property). Therefore, a lower members of S allotrops can form a vapours.
Calcium Chloride is the salt that is effective for melting ice on roads
The SI unit for measuring distance is the
meter.
I attached a table of SI measurements for you :)
Hope this helped!