The Avogadro Constant NA is well-known as a fairly large quantity in some parts of the world it is called Loschmidts number, L, after the Austrian chemist who first estimated its value. But how large is it?
About 20 years ago a colleague in my then department rang me; he wanted to get a pile of sand with NA sand grains in it to show to his pupils. I said that if he could find a merchant to supply it then I would guarantee that the school would pay for it. Perhaps he would let me know how much he needed ..
For the sake of this order-of-magnitude calculation lets assume that each grain is a cube 0.1mm on a side, and that the grains pack perfectly with no spaces. Since it makes the calculation marginally easier, lets also deal with 1024 grains this is the same as the number of molecules in 30cm3 or a couple of tablespoonsful of water.
It is better if you go through the calculation. So we shall do it step by step; click on the Next button to move further through the document.
- If each grain is 0.1mm on a side, using our assumptions how many grains are there in a cubic metre?