Water’s Hydrogen

Bonds

ONE molecule of waterDraw 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 moleculeDid you know…

that one water drop of water is made up of roughly 5 million water molecules?

ONE molecule of waterIn a water molecule, H is behaving like a…

non-metal!Oxygen is a…non-metal!

Non-metal + Non-metal = what type of bond…?

Covalent bondsSo… 2 COVALENT BONDS are holding

together the 2H’s and 1 Oxygen! = one water molecule!

ONE molecule of waterIf 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

Oxygen

HydrogenHydrogen

Can you predict which atom doesn’t share evenly with the other atom and why?

ee

e

ee

e e

ee

e

pp

ONE molecule of waterBUT, 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 waterThe 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 waterWhen 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-

They bond because opposite partial charges will be attracted to each other between the water molecules!

(This is called POLARITY)

How many Water molecules do you see

here?

2

2

11

32

4 4

4

5

5

3

5

1

3

Water molecules bond to other water

molecules

-2

-2 -2

-2

-2

+1 +

1

+1

+1 +

1

+1

+1

+1

+1

+1 Positive

End +1 Hydrogen

Negative End-2 Oxygen

Water molecules bond to other water

moleculesThe 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 ActivityQ: 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 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.

What Happened with the drops of water on the penny?

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

-2

How many Hydrogen bonds are there in the diagram?

Place a star * where you think they are located.

-2 -2

-2

-2

+1 +

1

+1

+1 +

1

+1

+1

+1

+1

+1

Hydrogen Bonds in a Water Molecule Chain

-2

-2 -2

-2

-2

+1+1

+1

+1 +

1

+1

+1

+1

+1

+1

4

3

2

1

* * **

Water molecules bond to other water molecules

-2

How many Covalent bonds are there in the diagram?

Place an arrow with a (C) where you think a Covalent bond is.

-2 -2

-2

-2

+1 +

1

+1

+1 +

1

+1

+1

+1

+1

+1

Covalent Bonds in a Water Molecule Chain *

-2

Place a C where the Covalent bonds are located in the diagram below.

-2 -2

-2

-2

+1 +

1

+1

+1 +

1

+1

+1

+1

+1

+1

1

5,63, 4

2

78

9,10

Water WorksWe know one water molecule is made up of two

atoms and one atom. Since a water molecule is made up of two non-metal particles it has bonds holding it together. However, when we have many water molecules bonding together, they are held together by

bonds that are VERY weak! Water molecules bond because opposite attract! The hydrogen end of the water molecule will have a partial charge and the oxygen end will have a partial charge. Having these opposite charges means the water molecule hasBecause water loves

Hydrogen

partial charges

-2 Polarity.

Hydrogen

+1

Oxygen

itself!

Covalent