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Properties of water Cheat Sheet by

Properties of water notes from Dr. Georges's class.

Chemistry of water

- H2O molecules form hydrogen bonds with each other. The +Hydrogen is attracted to the -Oxygen which creates a "­Sticky Molecu­le".

Hydrogen Bonds Result in...

- good solvent
- cohesion & adhesion
- lower density as a solid
- high specific heat
- high vapori­zation rate

High Heat Vapori­zation

* It takes a long time for water to become vapor

High Specific Heat

H2O resists heat changes in temper­ature
- High specific heat
- Must add lots of heat to increase temper­ature
- Likewise must lose lots of heat to cool
H2O moderates earths temper­ature

Water Dissoc­iation (pH)

Water "­Dis­ass­oci­ate­s" meaning that...
+H = -O means water is neutral
+H > -O means water is acidic
+H < -O means water is basic
 

Lower Density as a solid #1

Most substances become denser when solid BUT NOT WATER!
- Ice floats; Hydrogen bonds create a lattice like structure in ice and becomes less dense than liquid water
- The lattice frame puts space between molecules

Lower Density #2 Why is this important?

* Oceans and lakes don't freeze solid
- Surface ice insulates water below
- This allows life to survive the winter
* If ice sank the lakes would freeze, fish would die in the winter and only the top layer of water would thaw.

Buffers in pH

Buffers: Something that keeps the pH the same or resists change
* pH effects shape and function of enzyme molecules
* pH can be stabilized with buffers. Ex: a reservoir of +H can donate more +H or absorb +H

pH Scale

* Measures the concen­tration of +H ions
* Measures acidic or basic (0-14)
* Each pH unit = ten-fold change in H+ ions ex: Moving from pH 1 (10 -1) to pH 2 (10 -2) = ten fewer +H ions
 

Cohesion and Adhesion #1

Cohesion and adhesion are what get water up a 300ft tree (and water potential and osmosis but that is in another chapter). Cohesion gets the water to stay together. Adhesion gets the waters to stick to the glucose and "­cli­mb".

Cohesion & Adhesion #2

Cohesion; sticking together and to itself
Adhesion; sticking to something else
- caused by the polar molecules
- attraction of water between other molecules
- causes surface tension
- Capilary Action; water "­cli­mbs­" up a cotton paper towel
 
- water likes/ climbs glucose and glass

Good Solvent #1

- polarity makes H2O a good solvent
- Polar H2O molecules surround + and - ions along with polar molecules (ex: carboh­ydrates & protiens)

Good Solvent #2

What dissolves in water?
What doesn't dissolve in water?
* Hydrop­hilic or "­water loving­" substances
* Hydrop­hobic or "­water fearin­g" substances
*They are attracted to water and are often polar
*They are not attracted to water and are often non polar
           

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