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

Do you remember? 2  What are the three main types of bonds?  Ionic, covalent, metallic  How do you predict which type will form?  Metal-non or non-non or metal-metal  What will O and H form? Why?  covalent bonds between H and O.  Because they are both nonmetals  But they have a special type of covalent bond called…POLAR.

There are three types of bonds you must know: 3 1. Metallic 2. Ionic 3. Nonpolar Covalent 4. Polar Covalent How do you know which type will form???

There are four types of bonds you must know: 4 1. Metallic- metal with a metal 2. Ionic 1. Metal with a nonmetal 2. OR if their electronegativities have a difference above 1.7

There are four types of bonds you must know: 5 Nonpolar Covalent: -Nonmetal with a nonmetal -If two of the same element -or if their electronegativity difference is ZERO

There are four types of bonds you must know: 6 Polar Covalent: -Nonmetal with a nonmetal -Electronegativity difference is between 0.1 and 1.6 -If Nitrogen, Oxygen or Fluorine are one of the elements, they are VERY electronegative and will hog the electrons… Therefore NOF’s create POLAR COVALENT BONDS!

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Properties of Water  It is polar…what does that mean?  WHY is it polar?

Polarity of Water  A water molecule is a polar molecule with opposite ends of the molecule with opposite charges.  oxygen is more electronegative so it pulls on the electrons more  So…the region around oxygen has a partial negative charge.  The region near the two hydrogen atoms has a partial positive charge. 9

This leads to a new type of bond…

11 Hydrogen bonding

HYDROGEN BONDS  The hydrogen bonds joining water molecules are weak, about 1/20 th as strong as covalent bonds.  They form, break, and reform with great frequency 12

H bonds give water some cool properties…  Water molecules arrange themselves in a very specific way…  WHY??? 13

14  The slightly negative regions of one molecule are attracted to the slightly positive regions of nearby molecules, forming a hydrogen bond. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 3.1 OPPOSITES ATTRACT

BUT Like charges repel each other… 15

Other cool properties of water…  Each water molecule can form hydrogen bonds with up to four neighbors.

Organisms Depend on H bonds…  Cohesion among water molecules plays a key role in the transport of water against gravity in plants  Adhesion, clinging of one substance to another, contributes too, as water adheres to the wall of the vessels. 17

18 Surface tension

Density of Water 19 The density of water: 1.Prevents water from freezing from the bottom up. 2.Ice forms on the surface first—the freezing of the water releases heat to the water below creating insulation. 3.Makes transition between season less abrupt.

20 Ice, water, vapor

21 Hydrogen bonding (electric attraction) IceLiquid

Are you afraid of water? 22  What do you think the following two words mean?  Hydrophilic  Hydrophobic  Hydro means water, philic and phobic refer to whether or not it “likes” water

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

“Like Dissolves Like” 24  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.

Food Coloring Demo  Food coloring does not dissolve in oil because it is polar and oil is NONPOLAR.

So what about oil and water? 26

Solvent for Life  Solution  Solute  Solvent  Hydrophilic  Ionic compounds dissolve in water  Polar molecules (generally) are water soluble  Hydrophobic  Nonpolar compounds 27