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  • Acids and bases are everywhere.

  • They're used to make foods,

  • soaps and detergents,

  • fertilizers,

  • explosives,

  • dyes,

  • plastics,

  • pesticides,

  • even paper.

  • Our stomachs are very acidic.

  • Our blood is slightly basic.

  • Our proteins are made up of amino acids,

  • and the letters in our genetic code,

  • those As, Ts, Cs, and Gs,

  • are all bases.

  • You were probably taught

  • how acids and bases behave

  • on the molecular level.

  • You were probably never taught

  • that a long time ago,

  • like ancient Greek ago,

  • before anyone knew about atoms or molecules,

  • acids and bases were defined

  • by how they behaved.

  • Acids tasted sour and corroded metal.

  • Bases felt slippery

  • and could somehow counteract acids.

  • When molecules dissolved in water interact,

  • they are exchanging two main currencies

  • with their surroundings:

  • protons, also known as hydrogen ions,

  • and electrons.

  • Depending on how a molecule is composed or shaped,

  • it may be willing to donate or accept

  • either protons or electrons

  • with some other community member.

  • And some molecules are far more aggressive than others

  • when it comes to donating or accepting either currency.

  • Remember that protons are positively charged

  • and electrons are negatively charged.

  • So, if a molecule is willing to give up a proton,

  • that's not too different

  • from it being willing to accept an electron --

  • either way it's becoming more negatively charged.

  • Other molecules are willing to accept a proton

  • or give up an electron.

  • These are becoming more positively charged.

  • Some substances are so aggressive

  • about donating their protons

  • that when they get a chance,

  • all of the molecules in a sample

  • will dump a proton,

  • sometimes more than one,

  • to the surrounding water molecules.

  • We call these strong acids.

  • Meanwhile, some compounds are so ready

  • to accept a proton

  • that they won't wait around,

  • they'll just rip one off water,

  • which usually has two protons

  • but is generous enough to hang out with just one.

  • We call these strong bases.

  • Other acids and bases are not so strong.

  • They may donate just a few of their protons to water

  • or accept just a few protons from water,

  • but most of their molecules stay exactly the same.

  • If left alone in water,

  • they'll reach some equilibrium point

  • where maybe only one out of a hundred

  • or one out of ten thousand of their molecules

  • has exchanged currency with water.

  • As you might guess,

  • we label these acids and bases weak,

  • but in the common sense of the word,

  • they're not weak.

  • The vinegar in your salad dressing

  • that you can smell from across the room,

  • that is a weak acid.

  • The ammonia you spray on glass

  • for a streak-free shine,

  • that is a weak base.

  • So, it doesn't take much to be an active player

  • in the chemical economy.

  • Most acid-base chemistry takes place in water,

  • which can act as either an acid or a base,

  • accepting deposits and enabling withdrawals

  • like a 24-hour molecular ATM.

  • And when a proton-deposit customer,

  • that's an acid,

  • and a proton-withdrawal customer,

  • the base,

  • shop at the same time,

  • their net effect on water's account

  • may cancel out,

  • and we call this neutralization.

  • Now, certain molecules can behave

  • as acids or bases without water,

  • but that's another story.

  • Let's end by saluting water

  • as the resilient and fair banker

  • for acids and bases.

  • It's always open for business,

  • doesn't charge interest,

  • and will never foreclose on your molecules,

  • which is more than I can say for [bleep].

  • Waah-waah.

Acids and bases are everywhere.

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B2 US TED-Ed proton water acid charged accept

【TED-Ed】The strengths and weaknesses of acids and bases - George Zaidan and Charles Morton

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    Kevin Tan posted on 2014/09/11
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