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Properties of Water

Hydrogen Bonds

� Hydrogen bonds do not join atoms …

� Hydrogen bonds are attractions between compounds

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WATERHydrogen Bonds Give Water Unique

Properties (Part I)

� Heat Storage

� A large input of thermal energy is required to disrupt the organization of liquid water

� This minimizes temperature changes

� High Heat of Vaporization

� At high temperatures, hydrogen bonds do break

� Water is changed into vapor resulting in a cooling effect

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Heat Storage & High Heat of Vaporization

• Water’s heat storage ability keeps temp of coastal areas more stable!

���� Properties of Water

Heat Storage & High Heat of Vaporization

• These properties allow water to trap lots of heat and take it away by evaporative cooling, like when you sweat!

• Ahhhhh …

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Ice Formation

•At low temperatures, hydrogen bonds don’t break•Water forms a regular crystal structure that floats

���� Ice is less dense than water, so

ice floats!

• This is super important because it prevents bodies of water from freezing solid and killing all life on the surface and underneath!

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Hydrogen Bonds Give Water Unique

Properties (Part II)

� Cohesion

� Attraction of water molecules to

other water molecules

� Example: Surface tension

� Adhesion

• Attraction of water molecules to

other polar molecules

• Example: Capillary action

Water strider

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Surface Tension!

� Cohesion (water to water) makes the surface of water like a

“solid” film!

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Capillary Action!

� Cohesion and Adhesion Allows for

Transpiration

- The movement of water up a plant

(by “capillary action”) because of

pull from evaporation through the

leaves.

���� Water is a Great Solvent:Hydrophilic & Hydrophobic Substances

� Hydrophilic (“water-loving”) substances

� Polar

� Hydrogen bond with water

� Example: sugar

� Hydrophobic (“water-fearing”) substances

� Nonpolar

� Repelled by water

� Example: oil

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Solution

� Solute- solid particles that dissolve

� Solvent-what causes dissolving

� Solution- homogenous mixture made from solute

and solvent

� Concentrated: when there is more solute than solvent

� Diluted: when there is more solvent than solute

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Solute + Solvent = Solution����

The pH Scale� Measures H+ concentration of

fluid

� Change of 1 on scale means 10X change in H+ concentration

Highest H+ Lowest H+

0---------------------7-------------------14

Acidic Neutral Basic

� BUFFERS

- Buffers are substances that resist pH changes!

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Acids & Bases

� Acids

� These substances cause water

to release its H+

� Acidic solutions have pH < 7

� Bases

� These substances grab H+

from water, leaving behind

OH- ions

� Basic solutions have pH > 7

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