Why doesn't a metre cube of box containing common salt weigh $2170\ kg$ if the density of NaCl lattice is $2170\ kg/m^3$?
As Mass = Volume x Density then for a unit volume shouldn't Mass= 1 x 2170= 2170 $kg$? What is the reason behind this?
Why doesn't a metre cube of common salt weigh 2170 kg if the density of NaCl lattice is 2170 kg/m^3?
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3$\begingroup$ Does your common salt contain air? $\endgroup$– Anders SandbergCommented Oct 7, 2018 at 14:35
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$\begingroup$ @AndersSandberg yeah, just what you would do when someone tells you to pack a metre cube of salt $\endgroup$– Vivek karunakaranCommented Oct 7, 2018 at 16:56
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1 Answer
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The sort of salt you use in the kitchen is made up from (approximately) cubic grains, and when you put these into a container then pack randomly with air gaps between the grains.
The packing fraction for randomly packed spheres is around 60%. I don't know what the figure for randomly packed cubes is, but I'd guess it will be similar. So the density of a box of salt grain will be around 60% of the density of a single salt crystal.
answered Oct 7, 2018 at 14:58
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$\begingroup$ So u mean that remaining 40% space would be occupied by air and this leading to a considerable reduction of weight? $\endgroup$ Commented Oct 7, 2018 at 16:55
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