Classroom Resources

Published on November 26th, 2012 | by Jo


Pass the small tweezers!

The great works of Chemistry that gave us the concept of molecules were done just over 200 years ago. [latexpage] In 1803, the Italian chemist Amedeo Avogadro showed that one mole of any substance contained approximately $6 \times 10^{23}$ molecules.

Each substance has its own molar weight. For water it is 18 grams, and that amount of water does not even fill a medicine cup (40 mL), yet it contains this stupendous number of molecules. What a tribute to the early researchers who deduced this fact!

How closely would the molecules in 18 grams of water (or 18 mL) be packed if we could spread them out (using some amazing little tweezers!):

a) evenly over the entire surface of the earth?

b) in a line from one end of the Milky Way galaxy to the other?[latexpage\]


Question created by Robert Nelder, Toowoomba State High School


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