1. WATER Physical Science ¾ of the Earth is covered with it Exists on Earth as a solid, liquid AND gas POLAR!!!

2. Do you remember the 3 types of bonds? 2 1. Metallic 2. Ionic 3. Covalent- actually there are two types… 1. Polar Covalent 2. Nonpolar Covalent How do you know which type will form???

3. So actually- there are four types of bonds you must know: 3 1. Metallic- 1. metal with a metal 2. Ionic 1. Metal with a nonmetal

4. The four types of bonds you must know: 4 3. Nonpolar Covalent: -Nonmetal with a nonmetal -If two of the same element

5. The four types of bonds you must know: 5 4. Polar Covalent: -Nonmetal with a nonmetal -If Nitrogen, Oxygen or Fluorine are one of the elements, they are VERY electronegative and will hog the electrons…and create POLAR COVALENT BONDS!

6. 6

7. Water background rewind  What elements are in a water molecule?  What type of bond will form between them?  How do you know it will be a polar covalent bond?  _______________ with a ____________

8. Polarity of Water  A water molecule is a polar molecule with opposite ends of the molecule having opposite charges.  oxygen is more electronegative so it pulls on the electrons more  So…  the OXYGEN end has a slight negative charge.  The HYDROGEN end has a slight positive charge. 8

9. This leads to a new type of “bond”…  Called a…

10. 10 Hydrogen bond

11. Hydrogen Bonds  Occur between molecules (not within)  Bonds within water molecules are POLAR COVALENT!!!

12. HYDROGEN BONDS  As far as BOND go, they are weak, about 1/20 th as strong as covalent bonds.  They form, break, and reform with great frequency 12

13.  Each water molecule can form hydrogen bonds with up to four neighbors. ** Label the polar covalent bonds and hydrogen bonds in your notes right now…

14. 14 Hydrogen bonds affect the properties of water

15. Special Arrangement:  Water molecules arrange themselves in a very specific way…  WHY??? 15

16. OPPOSITES ATTRACT

17. BUT Like charges repel each other… 17 H and H repel each other, as do O and O

18. 18 What two ends of the molecule attract each other? Hydrogen and Oxygen What will be repelled by each other? O + O and H + H Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 3.1 The slightly negative regions of one molecule are attracted to the slightly positive regions of nearby molecules, forming a hydrogen bond.

19. Properties of H bonds…  Cohesion – water molecules sticking to each other (by H bonds)  plays a key role in the transport of water against gravity in plants  Adhesion- water molecules stick to other things  Like the meniscus! 19

20. 20 Surface tensionMeniscus-adhesion Surface Tension- cohesion

21. Hydrophilic vs Hydrophobic  Hydrophilic  Any substance that likes water (WATER-LOVING) Ionic or polar substances Most hydrophilic substances dissolve in water (ex salt)  Hydrophobic: any substance that doesn’t like water  (WATER –FEARING) Usually nonpolar/non-ionic substance (ex-oil)

22. “Like Dissolves Like” 22  Polar Solutions (like water) are able to dissolve other polar molecules as well as ionic compounds. Why?  Likewise, nonpolar solutions (like oil) will not dissolve polar and ionic compounds and will instead dissolve NONPOLAR molecules.

23. Hydrophilic dissolves Hydrophilic WILL DISSOLVE: Ionic Compounds, Polar Molecules (anything with a charge) Water

24. Hydrophobic dissolves Hydrophobic WILL DISSOLVE: only nonpolar, hydrophobic things (things with NO CHARGE) Oil