We, the world, and all the universe are clumps of molecules. A molecule itself is made from smaller bits called atoms, but here I'm going to talk just a bit about molecules and a lot about their role in heat.

A molecule is a tiny blob. There are millions of kinds of molecules, depending on what atoms they are made of. Air is mostly a mixture of N2 and O2 molecules, where N2 is two joined atoms of nitrogen and O2 is two joined atoms of oxygen. Water is molecules of H2O--two atoms of hydrogen joined to an atom of oxygen. The earth's sandy beaches are largely quartz ground into the tiny particles. Quartz molecules are SiO2, an atom of silicon and two atoms of oxygen. The most complex molecules may have millions of atoms, usually including atoms of carbon. Although the universe is 75% hydrogen, oxygen is the most prevalent atom on the earth's surface; by weight it is roughly 25% of the air, 90% of the seas, and 50% of everything else.

When objects or parts of objects move, their molecules remain intact. As we move through air, its molecules flow around us. When we poke a finger in water, the molecules of our finger slide between the molecules of water. As we pull the finger out, little clumps of water molecules stay on the finger as moisture. (And a few molecules from our fingers remain in the water; but not enough to make a difference unless you are the Wicked Witch of the West.) When we split quartz, it cleaves between the molecules. A puff of air or jet of water is a stream of molecules, not individual atoms.

Bending a finger is a complex dance of many kinds of molecules. Skin, fat, and muscle molecules are connected loosely enough so they can flex. Each bone is a rigid collection of molecules. Two bones in a joint have sliding surfaces separatted by a thin layer of slippery molecules. Nerves and blood vessels are flexible tubes. Within nerves, chemical interactions pass signals from one end to another and across the junctions between nerves. (These junctions are not usually at the same place as the bone joint.) Within the blood vessels blood flows as a liquid of hemoglobin and a vast variety of other molecules.

There are two versions of hemoglobin. At the heart of both is an iron atom. In the lungs that atom grabs four oxygen atoms; it turns red exactly as the oxygen in the air combines with iron to form red rust. As the blood reaches an organ it releases the oxygen to the organ. The organ uses the oxygen to power various chemical interactions depending on what the organ is to do. In these reactions the oxygen winds up bound to other compounds that are carried away in the blood as waste, (Hemoglobin molecules are reused many times, but eventually break by losing essential atoms. The iron in the broken hemoglobin shows up as brown in the body's waste products.)

When I think of molecules, I tend to imagine something like a bunch of really small round chocolate sprinkles in a jar. But this fosters a hugely extravagant overestimate of the size of a molecule. Each chocolate sprinkle has something like half a billion billion molecules of chocolate. Or a cube almost 300 meters on a side. If that many sprinkles were melted into choclate bars we would have a quarter billion bars. If everyone on earth ate thirty a day, they would last a year.

wchoc = molecular weight of chocolate  (avg)
1 gm choc = AV / wchoc molecules
rchoc = density in gm/cc
CMC = choc molecules per cc = gm /rchoc = AV /wchoc/rchoc
sprinkle is 1/8000 cc  (.5mm cubed) 
CMS = choc molecules per sprinkle = CMC / 8000 

at wchoc = 100 and rchoc = 2
6e23  /wchoc/rchoc /8000 = 6e23 /1600000 


so if we have CMS sprinkles
we have CMS*CMS molecules
in gm this is 
	CMS * CMS / (AV /wchoc) gm
in 100gm bars this is
	CMS * CMS / AV / wchoc / 100 
(AV /wchoc /rchoc / 8000)2 / AV / wchoc / 100 
= AV / wchoc / rchoc2 / 80002/ 100 bars

or CMS sprinkles in cc is 
CMS2 / (AV / wchoc) / rchoc   
	= CMS *(AV/wchoc/rchoc/8000) / (AV / wchoc / rchoc) / rchoc
	= CMS / 8000 /rchoc
	= (AV/wchoc/rchoc/8000) / 8000 /rchoc 
	= (AV/wchoc/(rchoc/8000)2 
at wchoc = 100 and rchoc = 2
	= AV / (100*4*64000000) cc
	= 23437500000000 cc
this is a cube 286 meters on a side
or the space of 3000 houses

at wchoc = 100 and rchoc = 2

# bars = 6e23 /256e10 = 234375000000 = 234 billion bars
at 1/sec, almost 7432 years