1. Water’s Special Bond: Hydrogen Bonds

2. 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. H 2 O= one water molecule Did you know… that one water drop of water is made up of roughly 5 million water molecules?

3. 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… COVALENT BONDS are holding together the 2H’s and 1 Oxygen! = one water molecule!

4. 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!

5. 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)

6. 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.

7. 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.

8. ONE Molecule of Water -2-2  +1

9. 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!

10. How many Water molecules do you see here? 2 2 1 1 3 2 44 4 5 5 3 5 1 3

11. Water molecules bond to other water molecules  -2  +1 Positive End +1 Hydrogen Negative End -2 Oxygen

12. Water molecules bond to other water molecules The bonds that form between the water molecules are called Hydrogen bonds.Hydrogen bonds Hydrogen acts as a non-metal and Oxygen is a non-metal! So...ONE molecule of water is held together by COVALENT BONDS. Hydrogen bonds form because the opposite partial charges of molecules are attracted to each other. Hydrogen bonds are very weak. Water molecules are polar (positive and negative end) When two or more water molecules bond to each other, they use HYDROGEN BONDS.

13. Surface Tension 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?

14. Surface Tension This happens because the water molecules on the “outside” of the bubble hold on tighter to the inside molecules… they are forming stronger bonds. Think of a cheerleaders pyramid… The cheerleaders have to hold on tightest to the girls on the sides because they may fall off b/c they have no one else to hold onto.

15. 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  +1

16. Hydrogen Bonds in a Water Molecule Chain -2-2  -2  +1 4 3 2 1 * * * *

17. 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  +1

18. Covalent Bonds in a Water Molecule Chain  -2 Place a C where the Covalent bonds are located in the diagram below.  -2  +1 1 5,6 3, 4 2 7 8 9,10

19. Water Works We 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 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 has Because water loves Hydrogen partial charges attract! -2 Polarity. Hydrogen +1 Oxygen itself! Covalent