h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Very interesting and informative. I never even thought about what it took to remove grease from a plate. Nowadays when soap can be cheaply bought most of us are unaware of what it consists or have the time or inclination to make it.

I would respectfully suggest one, very minor modification for "How Soap Works".

"water molecules tend to separate into fragments with opposite electrical charges, one positive and one negative."

Water molecules are essentially oxygen atoms with two protons and electrons along for the ride. Normally, not that many of the water molecules "seperate into fragments". You can visualize a water molecule as a positively charged nucleus with four electron clouds around it. Two of the four are double electrons (negative) and two of the four are double electrons with a proton (positive relative to the other pair). Four clouds arrange themselves in a tetrahedron. Don't run, it simply means two are aligned north-south and the other two are above the first two, aligned east-west. Because one pair of pairs of electrons is more positive than the other pair of pairs of electrons, that end of the water molecule is more positive. That's what they mean by "polar".

Oil molecules and water molecules are both electrically neutral. Oil molecules are typically strings of carbons with hydrogens. The carbons in the middle of the string have four electron clouds, with two of the four having double electrons and two clouds having double electrons with a proton each (sound familiar?). It's kind of like a bunch of water tetrahedrons that are all in a row. Because you have a string of them, the polarities cancel out. The carbons on the ends don't have another carbon to bond to (since they're on the ends), so they typically have three proton/double electron clouds and one double electron cloud. Think of oil as a long worm with the positive clouds running in two ridges along the top and the bottom and the negative clouds running along each side.

By the way, the author is correct in saying that salt does fragment in water. In fact, when salt dissolves, some of the negatively charged chlorine atoms steal a proton from a water atom, causing it to "fragment" into H+ and OH-. That's why water softeners use salt to make water better able to dissolve things.

chartguy