- WELCOME TO THE VIDEO TUTORIAL ON INTERMOLECULAR FORCES.
INTERMOLECULAR FORCES ARE A REALLY ESSENTIAL CONCEPT.
IT IS IMPORTANT THAT YOU HAVE A CLEAR UNDERSTANDING OF THEM.
NOW IT'S A LOT OF SYLLABLES.
SO, WE'LL ABBREVIATE IT IMF'S.
WHAT ARE INTERMOLECULAR FORCES, RIGHT,
THIS IS ATTRACTION BETWEEN MOLECULES.
ALL RIGHT.
SO, WE HAVE COVALENT BONDS HOLDING THE ATOMS
TOGETHER TO CREATE THE MOLECULES.
SO, THEN THIS IS THE INTERACTION
BETWEEN TWO OR MORE INDEPENDENT MOLECULES.
NOW, THIS IS GOING TO--
THIS IS THE SOURCE OF POTENTIAL ENERGY
AND SO IF YOU'RE NOT SURE WHAT I MEAN ABOUT POTENTIAL ENERGY,
THERE IS A VIDEO TUTORIAL ON ENERGY AND--
KINETIC ENERGY AND POTENTIAL ENERGY THAT YOU CAN REFER TO.
SO, WE'RE GOING TO LOOK AT THE THREE MAIN FORMS
OF INTERMOLECULAR FORCES.
THE FIRST ONE IS DIPOLE-DIPOLE.
SO, FOR THIS INTERMOLECULAR FORCE TO OCCUR,
WE MUST HAVE POLAR MOLECULES.
AND SO, THEN AS THE MEAN WOULD IMPLY WE HAVE ONE POLAR MOLECULE
AND IT HAS A PARTIAL PLUS AND A PARTIAL MINUS.
AND SO THEN A SECOND MOLECULE IS GOING TO COME IN
AND IT'S GOING TO NATURALLY ORIENT
ITSELF TO MAXIMIZE THE ELECTROSTATIC ATTRACTION
AND MINIMIZE THE ELECTROSTATIC REPULSION.
SO IT WILL HAVE AN OPPOSITE ORIENTATION.
NOW, THE DIPOLE-DIPOLE IMF IS THIS ATTRACTION RIGHT
HERE BETWEEN THE TWO MOLECULES, ALL RIGHT?
SO IT'S A CONSTANT ATTRACTION.
AND SO THEN IF I DREW IN A THIRD MOLECULE,
YOU COULD IMAGINE HOW IT WOULD ORIENT, RIGHT,
ITS PARTIAL NEGATIVE WOULD COME IN
AND A LINE UP OPPOSITE THE PARTIAL POSITIVE.
SO, THIS DASH THREAD LINES REPRESENT
ALL OF THE DIPOLE-DIPOLE INTERMOLECULAR FORCES.
SO, IT'S THE ATTRACTION
THAT BETWEEN TWO OR MORE POLAR MOLECULES
AND WE KNOW THAT THEY'RE GOING TO ORIENT
THEMSELVES TO MAXIMIZE ATTRACTION
AND MINIMIZE REPULSION. OKAY.
NOW DIPOLE-DIPOLE I THINK IS PRETTY STRAIGHTFORWARD,
H-BONDING IS A REALLY TERRIBLE NAME
BECAUSE THEY'RE NOT TRUE CHEMICAL BONDS,
IT'S AN INTERMOLECULAR FORCE
AND IT'S A CASE OF EXTREME DIPOLE-DIPOLE.
SO WHY SO EXTREME, WHAT MAKES THIS SPECIAL?
WELL, H-BONDING ONLY OCCURS--
NOW, QUITE NATURALLY THERE'S GOING TO BE HYDROGEN
THERE SO IF WE HAVE MOLECULES
WHERE THERE'S A NITROGEN ATOM BOND TO A HYDROGEN,
RIGHT, AND THEN
OF COURSE NITROGEN LIKES TO HAVE THREE BONDS AND ITS LONE PAIR
OR WE CAN HAVE AN OXYGEN BONDED TO A HYDROGEN
OR WE CAN HAVE FLUORINE BONDED TO A HYDROGEN.
NOW, WHAT MAKES THIS SO SPECIAL, RIGHT?
WHEN WE LOOK AT ELECTRONEGATIVITIES,
AND THERE'S ALSO A VIDEO TUTORIAL ON ELECTRONEGATIVITIES,
SO IF YOU'RE NOT--
YOU FEEL LIKE YOUR UNDERSTANDING
OF ELECTRONEGATIVITIES COULD DO SOME HELP,
I'LL REFER YOU TO THAT VIDEO TUTORIAL,
RIGHT, AND SO WE REMEMBER RIGHT,
THAT FLUORINE WAS THE MOST ELECTRONEGATIVE, RIGHT?
SO THESE ARE THREE OF THE MOST ELECTRONEGATIVE ATOMS
OR ELEMENTS.
AND WHEN THEY'RE BONDED TO HYDROGEN, RIGHT,
REMEMBER POOR LITTLE HYDROGEN, RIGHT?
HYDROGEN ONLY HAS ONE PROTON.
SO, IT DOES NOT HAVE A VERY STRONG ABILITY
TO PULL ON THE ELECTRONS.
SO, WHAT MAKES H-BONDING
AN EXTREME DIPOLE-DIPOLE IS THAT WE HAVE THE LARGEST DIFFERENCES
IN ELECTRONEGATIVITY,
RIGHT, THERE'S MEANS-- RIGHT?
ANOTHER WAY TO SAY THAT IS THESE ARE THE MOST POLAR BONDS,
RIGHT, AND THEN IT COMES DOWN TO A SIZE THING,
THE SMALL SIZE
OF HYDROGEN ALLOWS THE TWO INDEPENDENT MOLECULES
TO GET VERY CLOSE TOGETHER
WHICH STRENGTHENS THEIR ATTRACTION.
OKAY? SO, THE SMALL SIZE OF HYDROGEN--
RIGHT, SO WE HAVE THE TWO REASONS.
WE HAVE THE LARGE DIPOLE MOMENT,
THE LARGE DIFFERENCES IN ELECTRONEGATIVITY,
SO THESE ARE VERY POLAR BONDS
AND THEN WE HAVE THE SMALL SIZE OF HYDROGEN,
ALLOWS THE MOLECULES TO GET VERY CLOSE PHYSICALLY,
RIGHT, AND THAT--
SO THESE TWO THINGS INCREASE THE STRENGTH
OF THE INTERMOLECULAR FORCE TO THE POINT
THAT WE GIVE IT ITS OWN NAME.
SO, OF COURSE THEY'RE GOING TO BE VERY CLOSE
BUT IF I TRY TO DRAW THIS,
I WON'T BE ABLE
TO ILLUSTRATE IT IF I SHOW THEM TOO CLOSE SO I'LL KEEP--
I'LL STILL KEEP A LITTLE DISTANCE, RIGHT?
SO, HERE'S OUT TWO--
HERE'S OUR WATER MOLECULE
AND WHEN WE LOOK AT THE WATER MOLECULE,
RIGHT, WE CAN'T HELP BUT SEE THE DIPOLE MOMENT RIGHT HERE
AND SO THEN IF A SECOND WATER MOLECULE COMES IN,
IT'S GOING TO ORIENT ITSELF IN THE OPPOSITE DIRECTION
SO THAT WE--
JUST LIKE WE SAW UP ABOVE FOR THE DIPOLE-DIPOLE, ALL RIGHT?
SO THESE TWO WATER MOLECULES ARE
GOING TO ORIENT THEMSELVES AND THEN HERE COMES THE H BOND,
RIGHT, THE H BOND IS THE INTERMOLECULAR FORCE
THAT HOLDS THESE TWO WATER MOLECULES TOGETHER, RIGHT?
SO IT'S IMPORTANT THAT WE KEEP THIS STRAIGHT.
THIS RIGHT HERE, RIGHT,
THIS BOND RIGHT HERE THAT'S A POLAR COVALENT BOND,
ALL RIGHT?
THIS ATTRACTION BETWEEN THE TWO INDEPENDENT WATER MOLECULES,
THAT'S THE H-BONDING.
SO, IT'S THE SAME IDEA AS DIPOLE-DIPOLE
EXCEPT BECAUSE OF THE LARGE DIFFERENCE IN ELECTRONEGATIVITY,
THEN THE SMALL SIZE OF HYDROGEN, IT ALLOWS--
IT GIVES A MUCH STRONGER FORCE.
SO, IF I COULD DEMONSTRATE WITH MY HANDS, IF--
AS KIDS,
DO YOU EVER GOT THE CHANCE OR EVEN AS AN ADULT
IF YOU HAD TWO BAR MAGNETS AND WE HOLD THE BAR MAGNETS
FAR APART THEN THAT WILL SYMBOLIZE THE CHARGES,
RIGHT, AND SO IF I HAVE THESE TWO MAGNETS FAR APART,
I CANNOT--
ONE MAGNET DOES NOT FEEL THE OTHER MAGNET
BUT NOW AS I BRING THE MAGNETS CLOSER AND CLOSER TOGETHER,
WE START TO FEEL THAT ELECTROSTATIC ATTRACTION
OR REPULSION OR THE MAGNETIC ATTRACTION OR REPULSION
AND AS WE GET CLOSER AND CLOSER TOGETHER,
FINALLY WE GET SO CLOSE THAT THE ATTRACTION
JUST OVERCOMES AND THEY'LL GET STUCK TOGETHER.
SO, THAT'S WHAT HAPPENS WITH THE SMALL SIZE OF HYDROGEN.
THE MOLECULES ARE ALLOWED TO GET SUPER CLOSE WITH STRINGS
SINCE THEY'RE ATTRACTION TO EACH OTHER.
ALL RIGHTY.
SO, NOW WE'LL LOOK AT ONE MORE TYPE OF INTERMOLECULAR FORCE
AND THIS IS CALLED THE LONDON FORCE.
AND THIS ONE IS INTERESTING BECAUSE FIRST OF ALL,
THIS ONE HAS A BUNCH OF NAMES, ALL RIGHT?
SO, IT'S ALSO CALLED THE DISPERSION FORCE
AND IN MOST OF THE BIOLOGY TEXT,
IT'S REFERRED TO AS VAN DER WAALS.
IT ALSO GETS CALLED AN INSTANTANEOUS DIPOLE
OR IT GETS CALLED INDUCED DIPOLE
OR IT GETS CALLED A HYDROPHOBIC INTERACTION.
SO, THIS INTERMOLECULAR FORCE GOES BY A LOT OF NAMES.
SO DEPENDING ON HOW HEAR IT DESCRIBED,
IT'S ALL DESCRIBING THE SAME INTERMOLECULAR FORCE.
AND WHAT'S IMPORTANT ABOUT THIS ONE, RIGHT,
IT'S FOR NON-POLAR MOLECULES.
NOW, THIS MAY SEEM VERY STRANGE
BECAUSE WHEN WE TALK ABOUT DIPOLE-DIPOLE AND H-BONDING,
IT WAS ALL ABOUT HAVING THOSE DIFFERENCES
IN ELECTRONEGATIVITY
AND THE PARTIAL POSITIVE AND PARTIAL NEGATIVE CHARGE.
SO, HOW IN THE WORLD DOES THIS DIPOLE WORK?
WELL, LET'S SAY WE HAVE THIS LARGE NON-POLAR MOLECULE.
SO, LET'S THINK BACK TO WHAT WE KNOW ABOUT THE STRUCTURE
OF ATOMS AND MOLECULES.
WHEN WE HAVE THE NUCLEUS OF THE ATOM
AND LET'S SAY WE GROW IT UP TO BE THE SIZE OF A GRAPE,
RIGHT, SO IF THE NUCLEUS
OF AN ATOM IS THE SIZE OF THE GRAPE,
THE ELECTRONS CAN BE UP TO A MILE AWAY, RIGHT?
SO IF I'M HOLDING THE NUCLEUS OF AN ATOM IN THE PALM OF MY HAND
AND IT'S THE SIZE OF A GRAPE,
THE ELECTRONS COULD BE ALL THE WAY TO HIGHWAY 99, BROADWAY,
FRUITRIDGE AND I-5, RIGHT?
THERE'S A LOT OF EMPTY SPACE INSIDE OF ATOMS AND MOLECULES.
AND THE ELECTRONS ARE BUSY WHIRLING AROUND.
SO, WHAT CAN HAPPEN
IN THESE NON-POLAR MOLECULES IS FOR JUST AN INSTANT,
WE HAVE LIKE ELECTRON PILE UP,
A LITTLE ELECTRON GRIDLOCK RIGHT THERE.
BUT THEN, THAT MEANS IF THE ELECTRONS ARE
PILED UP OVER HERE,
THERE MUST BE SOME ELECTRONS MISSING OVER HERE,
BUT IT'S A VERY WEAK,
INSTANTANEOUS EFFECT.
SO, NOW IF THERE'S A NEIGHBORING MOLECULE THAT'S ALSO NON-POLAR,
RIGHT, BUT AS SOON AS WE GET SOME CHAOS OVER HERE,
IF THERE'S A PARTIAL POSITIVE HERE,
THE ELECTRONS IN THIS NON-POLAR MOLECULE,
THEY JUST GET ALL EXCITED AND ATTRACTED
TO THAT POSITIVE CHARGE AND THEY RUSH OVER.
AND IF THOSE ELECTRONS RUSH OVER,
THAT MEANS THEY'RE MISSING FROM SOMEWHERE ELSE.
AND SO JUST FOR A MOMENT,
WE ARE GOING TO HAVE A VERY WEAK,
VERY TEMPORARY DIPOLE MOMENT.
SO, THAT'S WHY SOMETIMES IT'S CALLED INDUCED
BECAUSE IT RIPPLES THROUGH.
IT'S ALSO GETS CALLED DISPERSION
BECAUSE THE MORE SURFACE AREA WE HAVE IN A MOLECULE,
THE LARGER THE MOLECULE IS, THE MORE LIKELY
THERE'S A CHANCE THAT WE'LL GET SOME ELECTRON ANARCHY HERE
AND GET ONE OF THESE INSTANTANEOUS DIPOLES.
AND VAN DER WAALS IS THE NAME
OF A GENTLEMAN THAT FIRST PROPOSED THIS.
ALL RIGHTY.
SO NOW, NOTICE, RIGHT, THESE ARE NON-POLAR MOLECULES.
SO IF WE COME BACK LATER IN TIME, RIGHT,
THERE'S NO PERMANENT DIPOLE MOMENT.
SO, JUST BECAUSE THERE WAS A PARTIAL NEGATIVE
HERE A WHILE AGO,
THAT PARTIAL NEGATIVE COULD HAVE MOVED.
AND THEN MAYBE THE PARTIAL POSITIVE'S OVER HERE
AND THEN THAT WOULD INDUCE THE DIPOLE HERE
THAT COULD END UP WITH A PARTIAL NEGATIVE THERE.
AND SO THEN, ONCE AGAIN, WE GET A VERY WEAK ATTRACTION,
A VERY TEMPORARY ATTRACTION
BETWEEN THESE NON-POLAR MOLECULES.
AND SO THE LARGER THEY ARE,
THE MORE DOMINANCE THIS LONDON FORCE WILL HAVE IN KEEPING
THE MOLECULES ATTRACTED TO EACH OTHER.
SO NOW THAT WE'RE FAMILIAR
WITH THE THREE PRIMARY INTERMOLECULAR FORCES,
LET'S LOOK AT THEIR RELATIVE STRENGTH, ALL RIGHT?
SO, WE'LL PUT THE STRONGEST OVER HERE, ALL RIGHT?
SO OF COURSE, THAT'S GOING TO BE H-BONDING.
RIGHT, BECAUSE THAT'S OUR EXTREME DIPOLE-DIPOLE,
THAT'S THE LARGEST INTERMOLECULAR,
THE-- OR THE LARGEST DIPOLE MOMENT WITH A SMALL
ATOMIC SIZE OF HYDROGEN.
AND THEN THAT WILL BE GREATER THAN THE DIPOLE-DIPOLE
WHICH STILL HAS THE PERMANENT DIPOLE MOMENTS.
BUT THEY'RE NOT AS STRONG.
AND THEN OF COURSE THE WEAKEST IS GOING TO BE THE LONDON
WHERE THEY'RE TEMPORARY.
ALL RIGHTY.
SO NOW I WOULD LIKE TO GIVE YOU AN AUDIO VERSION
OF INTERMOLECULAR FORCES. ALL RIGHT?
SO WITH H-BONDING, IT'S HIGHLY POLAR,
REALLY LARGE, SO IF WE THINK ABOUT H-BONDING IT WOULD BE LIKE
[MAKES NOISE]
RIGHT? IT'S REALLY STRONG AND IT'S A CONSTANT ATTRACTION.
DIPOLE-DIPOLE ON THE OTHER HAND,
IS A WEAKER DIPOLE MOMENT BUT IT'S CONSTANTLY PRESENT,
SO THAT WOULD BE MORE LIKE
[MAKES NOISE]
AND THEN IF WE LOOK LONDON FORCE IN TERMS OF AUDIOS EXPERIENCE,
IT WOULD BE LIKE
[MAKES NOISE]
VERY WEAK AND TEMPORARY, RIGHT?
SO H-BONDING IS CONSTANTLY PRESENT AND STRONG
[MAKES NOISE]
RIGHT? DIPOLE-DIPOLE,
CONSTANTLY PRESENT BUT WEAKER
[MAKES NOISE]
AND THEN LAST BUT NOT LEAST, LONDON
[MAKES NOISE]
RIGHT? AND THAT IS REPRESENTING THE POTENTIAL ENERGY
THAT IS HOLDING THESE MOLECULES TO EACH OTHER.
SO WHEN WE LOOK AT MOLECULES, WE WANT TO BE ABLE
TO IDENTIFY THE DOMINANT INTERMOLECULAR FORCE.
SO THE FIRST THING WE'RE GOING TO ASK OURSELF, RIGHT?
IS POLAR OR NON-POLAR?
SO IF WE LOOK AT THIS MOLECULE HERE,
WE WANT TO SEE IT IN ITS THREE-DIMENSIONAL SHAPE
AND WE RECOGNIZE THAT THERE ARE POLAR BONDS
BUT THEY'RE ALL RADIATING OUT INTO THE CORNERS
OF THE TETRAHEDRON.
SO EVEN THOUGH WE CAN'T WRITE DIPOLE MOMENT ARROWS, OVERALL,
THE MOLECULE IS NON-POLAR.
AND FOR ALL NON-POLAR MOLECULES,
THE DOMINANT INTERMOLECULAR FORCE IS THE LONDON FORCE.
NOW, THIS NEXT MOLECULE, RIGHT,
IT'S REALLY IMPORTANT
TO REMEMBER YOUR THREE-DIMENSIONAL SHAPES.
SO, IF YOU'RE WONDERING HOW I
JUMPED FROM THIS LEWIS STRUCTURE TO THIS SHAPE HERE,
YOU'RE GOING TO--
I WOULD ENCOURAGE YOU TO WATCH
THE MOLECULAR SHAPE VIDEO TUTORIAL.
SO HERE, WE RECOGNIZE THIS MOLECULE IS ALSO
IN A TETRAHEDRAL SHAPE AND SO NOW,
WE HAVE OUR TWO DIPOLE MOMENTS,
THEY'RE POINTING IN THE SAME DIRECTION,
SO WE END UP WITH A POLAR MOLECULE.
ONCE WE HAVE A POLAR MOLECULE, WE NEED TO ASK OURSELVES,
IS IT DIPOLE-DIPOLE OR H-BONDING, RIGHT?
SO THIS ONE'S EASY,
THERE'S NO WAY THAT WE CAN HAVE H-BONDING HERE
BECAUSE THERE ARE NO NITROGENS,
OXYGENS, OR FLOURINES.
SO WE WOULD DESCRIBE THIS AS DIPOLE-DIPOLE. OKAY.
NOW, WE LOOK AT OUR THIRD MOLECULE.
REMEMBER WITH CARBONS AND HYDROGENS,
THEY HAVE SIMILAR ELECTRONEGATIVITIES
SO WE DO NOT-- WE NEVER DRAW DIPOLE MOMENT ARROWS
BETWEEN CARBONS AND HYDROGENS.
BUT OXYGEN IS TO THE RIGHT OF CARBON AND SO
WE GET A DIPOLE MOMENT THERE.
ANYTIME WE HAVE A MOLECULE WITH ONLY ONE DIPOLE MOMENT,
WE KNOW IT'S POLAR. OKAY.
NOW, THIS ONE COULD BE A LITTLE TRICKIER.
WE HAVE OXYGEN AND WE HAVE HYDROGEN
BUT THEY ARE NOT BONDED TO EACH OTHER.
SO ONCE AGAIN, THIS IS AN EXAMPLE OF DIPOLE-DIPOLE.
NOW, WE'LL LOOK AT THE LAST EXAMPLE
SO WE CAN COMPARE OUR THIRD EXAMPLE TO OUR FOURTH EXAMPLE.
HERE, RIGHT, WE ALWAYS IGNORE, THERE'S NO POLARITY,
THAT'S SIGNIFICANT BETWEEN CARBONS AND HYDROGENS.
SO THERE'S NO DIPOLE MOMENTS THERE, RIGHT?
BUT HERE WE HAVE-- BETWEEN OXYGEN AND HYDROGEN,
WE HAVE A VERY LARGE DIPOLE MOMENT.
AND THEN BETWEEN THE CARBON AND THE OXYGEN,
WE WOULD HAVE A SMALL DIPOLE MOMENT.
SO THIS MOLECULE IS DEFINITELY POLAR.
AS SOON AS IT'S POLAR, NOW WE SEE, YES, RIGHT?
WE HAVE OUR OH-BOND WHICH LETS US KNOW THAT THIS--
THE DOMINANT INTERMOLECULAR FORCE
HERE WILL BE H-BONDING, OKAY?
SO IT'S IMPORTANT TO MAKE THE DISTINCTION
BETWEEN EXAMPLE THREE
WHERE OXYGEN IS PRESENT VERSUS OXYGEN BEING BONDED TO HYDROGEN
IN THIS LAST EXAMPLE. ALL RIGHTY.
SO, LET'S HAVE ONE LAST PAGE TO APPLY,
SHOW A COUPLE EXAMPLES OF WHERE INTERMOLECULAR FORCES COME IN
AND ONE LITTLE PRACTICE PROBLEMS LEFT. OKAY.
SO ARE THE FOLLOWING PURE COMPOUNDS CAPABLE OF H-BONDING?
SO IF WE LOOK AT THIS COMPOUND A HERE, WE SEE, RIGHT?
WE SEE NH-BONDS, SO WE WOULD SAY, YES.
FOR THIS SECOND EXAMPLE,
WE DEFINITELY HAVE OXYGEN, RIGHT?
AND WE HAVE HYDROGEN, RIGHT?
BUT THERE'S NO OH-BONDS.
SO WE WOULD SAY NO.
NO H-BONDING.
AND ONE OF THEIR--
HUNDRED OF EXAMPLES OF HOW INTERMOLECULAR FORCES SHOW UP
IN OUR BIOCHEMISTRY AND PHYSIOLOGY AND EVERYTHING
SO JUST A QUICK LITTLE TEASER TO HELP--
HAVE YOU FEEL MOTIVATED AND PASSIONATE
ABOUT INTERMOLECULAR FORCES BECAUSE THEY ARE SO IMPORTANT.
BASICALLY THE TWO STRANDS OF OUR DNA THAT CREATE A DOUBLE HELIX,
THEY'RE HELD TOGETHER BY H-BONDS.
IT'S LIKE A ZIPPER.
AND SO, WE WILL BE STUDYING THE STRUCTURE OF DNA LATER
AND THE TERM BUT HERE ARE THE NITROGENOUS BASES
AND SO THESE DASHED LINES HERE,
THESE ARE THE H-BONDS THAT HOLD THE TWO STRANDS OF DNA TOGETHER.
AND SO NOW IF WE CIRCLE
IN TO WHERE WE HAVE CYTOSINE AND GUANINE,
SO WE GET A CLOSER VIEW OF THE DNA, WE CAN SEE HERE,
RIGHT, HERE IS OUR NH, SO WHEN WE SEE THIS,
WE SEE A PARTIAL PLUS ON THE HYDROGEN
AND A PARTIAL MINUS ON THE NITROGEN.
AND NITROGENS ARE ELECTRONEGATIVE
SO THERE'S A PARTIAL MINUS.
HERE'S ANOTHER PARTIAL MINUS ON THIS MOLECULE, ALL RIGHT?
AND NOW WE'LL LOOK AT THE OTHER NITROGENOUS BASE, RIGHT?
OXYGENS ARE VERY ELECTRONEGATIVE,
WHEN YOU SEE THEM THEY'RE GOING TO HAVE A PARTIAL MINUS.
HYDROGEN, PARTIAL PLUS, PARTIAL MINUS,
PARTIAL PLUS, PARTIAL MINUS.
SO HERE WE CREATE, HERE ARE THE H-BONDS.
SO THIS HYDROGEN WITH ITS STRONG PARTIAL POSITIVE
IS GOING TO BE ATTRACTED TO THE OXYGEN
WITH ITS STRONG PARTIAL NEGATIVE.
AND THEN THE SAME THING HAPPENS HERE AND HERE.
SO THERE ARE THREE H-BONDS THAT KEEP THESE TWO--
THAT HELPED TO LOCK TOGETHER OUR DNA STRANDS.
AND SO THEN IT BECOMES LIKE A ZIPPER.
SO WE CAN OPEN AND CLOSE OUR DNA
BY EITHER BREAKING THESE HYDROGEN BONDS
OR REFORMING THEM.
SO THERE IS AN OVERVIEW OF THE FUNDAMENTALS
OF INTERMOLECULAR FORCES.
SO THIS WOULD BE A GOOD TIME TO GO BACK THROUGH YOUR NOTES
AND WORK A COUPLE OF HOMEWORK PROBLEMS
TO REINFORCE YOUR UNDERSTANDING.