Question: How many molecules are in a centimetre? ( can rob please answer this?)

Robert Woolfson answered on 6 Mar 2015:

Short answer: We’d get about 10 million molecules lined up side by side in once centimetre.

Long answer:
Alright. Molecules come in all shapes and sizes so that’s a tricky question. To answer, we can say that a molecule is one nanometre big. There are one billion nanometres in a metre, so we could line up one billion molecules in a one metre straight line. Now, a centimetre is 100 times smaller than a metre. This means that in one centimetre we would have 10 million molecules lined up perfectly side by side.

If, instead of a straight line, you have a cube of 1 cm3 (each side is 1 cm), things get a bit crazy. We’d end up with 10 million cubed, or 10 sextillion molecules (1 with 22 zeroes after it). That’s a bigger number than how long the universe has existed in seconds, 50 quadrillion seconds (5 with 17 zeroes after it).

In reality, molecules don’t really like getting too close to each other (relatively speaking). When you try and make two molecules get close to each other, most of the time they start pushing away from each other. This means that if we tried to measure this in real life we’d get numbers much smaller than I’ve said above as the molecules wouldn’t be perfectly side by side.

If two molecules do get really close to each other and instead of pushing apart, they start doing things to each other, then we call it chemistry.