Water’s
Hydrogen
Bonds
ONE molecule of water
Draw what you think a water molecule looks like!
We know that…
ONE molecule of water is made up of 2H’s
and 1 Oxygen.
H2O= one water molecule
Did you know…
that one water drop of water is made up
of roughly 5 million water molecules?
ONE molecule of water
In a water molecule, H is behaving like a…
non-metal!
Oxygen is a…
non-metal!
Non-metal + Non-metal = what type of bond…?
Covalent bonds
So… 2 COVALENT BONDS are holding
together the 2H’s and 1 Oxygen! = one water
molecule!
ONE molecule of water
If the 2H’s and 1 Oxygen are
being held together by Covalent
bonds that means that they are
SHARING…
valence electrons!!!
Now Draw a water molecule using Bohr Models!
Water Molecule Bohr Model
Can you predict which atom doesn’t share evenly with the
other atom and why?
e
e
Oxygen
e
e
e
e
Hydrogen e
p
e
e
e
Hydrogen
p
ONE molecule of water
BUT, the Oxygen atom is much bigger and
stronger than the little Hydrogen atoms…
So the Oxygen is NOT sharing the valence
electrons evenly with the Hydrogen atoms.
(Like a big brother picking on his little brother)
ONE molecule of water
The Oxygen is pulling the electrons
away from the Hydrogen atoms and into
itself.
Since electrons have a negative charge
this means that the Oxygen atom in
water is no longer neutral.
Oxygen Now it has a partial charge that
is -2.
ONE molecule of water
When the Oxygen atom pulls the
electrons away from the Hydrogen
atoms this causes the 1p+ in Hydrogen’s
nucleus to be exposed.
Since protons are positive this means
that the Hydrogen atoms now have a
partial +1 charge.
ONE Molecule of Water
-2
 +1
 +1
Water molecules bond to other
water molecules*
Since water molecules have partial charges…
*Remember that…
The Oxygen end is negative and the Hydrogen
end is positive (This is called POLARITY)
They bond because opposite partial charges
will be attracted to each other between the
water molecules!
How many Water molecules
do you see here?
5
5
1
5
1
4
1
4
2
2
2
3
3
3
4
Water molecules bond to
other water molecules
+1
Positive End
+1 Hydrogen
+1
+1
Negative End
+1
-2 Oxygen
-2
+1
+1
+1
+1
+1
+1
Water molecules bond to
other water molecules
The bonds that form between many water molecules are
called Hydrogen bonds.
Hydrogen acts as a non-metal and Oxygen is a non-metal!
So...ONE molecule of water is held together by
2 COVALENT BONDS.
Hydrogen bonds form because the opposite partial charges
of molecules are attracted to each other.
When two or more water molecules bond to each other,
they use HYDROGEN BONDS.
Properties of
Hydrogen Bonds
• Hydrogen bonds are very weak bonds.
• Water molecules are polar (positive and negative end)
• Water can cause surface tension
Water Penny Activity
Q: Have you ever seen water on top of a
penny???
The water will form a bubble on top of
the penny… it doesn’t just flatten out
and spill off.
How many drops can fit on a penny?
Write a prediction on your paper.
What Happened with the drops
of water on the penny?
What happens is the water molecules on
the “outside” of the bubble hold on tighter
to the inside molecules… they are forming
stronger bonds.
Surface Tension
At the surface of any liquid, the molecules
attract each other. The surface layer is in
tension, called surface tension, which
causes the surface of the liquid to act like
an elastic skin containing the liquid.
Surface Tension Activity
Surface Tension
In this activity, you will
study surface tension and
the effect that surfactants
(materials that reduce the
surface tension of liquids)
have on it.
Can you make a Paper
Clip float on water?
Floating Paper Clip due to
Surface Tension
Hydrogen bonds
holding tightly
around the paper
clip!
Water molecules bond to other
water molecules
How many Hydrogen bonds are there in the diagram?
Place a star * where you
+1
think they are located.
+1
+1
+1
-2
+1
+1
+1
+1
+1
+1
Hydrogen Bonds in a Water
Molecule Chain
4
+1
+1
+1
-2
*
+1
+1
+1
1
*
3
2
*
+1
*
+1
+1
+1
Water molecules bond to other
water molecules
How many Covalent bonds are there in the diagram?
Place an arrow with a (C)
+1
where you think a
Covalent bond is.
+1
+1
+1
-2
+1
+1
+1
+1
+1
+1
Covalent Bonds in a Water
Molecule Chain *
Place a C where the Covalent bonds are located in
the diagram below.
+1
9,10
1
+1
+1
7
+1
2
-2
3, 4
+1
+1
8
+1
+1
+1
+1
5,6
Water Works
We know one water molecule is made up of two
atom.
Since
Hydrogenatoms and one
Oxygen
a water molecule is made up of two non-metal particles it
has Covalent
bonds holding it together. However, when
we have many water molecules bonding together, they are
held together by Hydrogen bonds that are VERY weak!
Water molecules bond because opposite partial charges
attract! The hydrogen end of the water molecule will have
a partial +1 charge and the oxygen end will have a partial
-2 charge. Having these opposite charges means the
water molecule has Polarity.
Because water loves itself!