Properties of Water

Is water polar or non-polar

Polar

Hydrogen bond

slightly negative O attracted to slightly positive H of nearby molecule

How many bonds can H2O form?

4

4 important properties of water?

1. Cohesive Behavior

2. Moderation of Temperature

3. Expansion Upon Freezing

4. Solvent

Cohesion

H-bonding between like molecules

Surface Tension

measure of how difficult it is to break or stretch surface of liquid

Adhesion

bonding between unlike molecules

(eg. Adhesion of H2O to plant vessel walls counters downward pull of gravity)

Transpiration

movement of H2O up plants

H2O clings to each other by __________; cling to xylem tubes by ___________

cohesion, adhesion

Transpiration

Water transport in plants

Thermal energy (heat)

Total amount of kinetic energy(KE) in system

Temperature

measure intensity of heat due to average kinetic energy(KE) of molecules

Water specific heat

It has a high specific heat → 4,184 Joules

What does the high specific heat of water contribute to?

Change temp less when absorbs/loses heat

Large bodies of water absorb and store more heat = warmer coastal areas

Create stable marine/land environment

Humans ~65% H2O = stable temp, resist temp. change

Water has high heat of

vaporization

What molecules leave as gas in water vapor

Molecules with greatest KE(kinetic energy)

What does evaporative cooling of water contribute to?

Stable temp in lakes & ponds

Cool plants

Human sweat = natural cooling

Insulation by ice

less dense, floating ice insulates liquid H2O below

What does Insulation by ice contribute to?

1. Life exists under frozen surface (ponds, lakes, oceans)

2. Ice = solid habitat (polar bears)

Solution

liquid, homogeneous mixture of 2+ substances

Solvent

dissolving agent (liquid)

Solute

dissolved substance

Water is a….

versatile solvent

Hydrophilic properties

Affinity for H2O

Polar, ions

cellulose, sugar, salt

blood

Hydrophobic properties

Repel H2O

Non-polar

Oils, lipids

cell membrane

Water dissociate equation thing (idk what im doing)

H2O <=> H+ + OH-

acid or base will ________ the balance of these two ions in solution.

change

in a neutral substance, these ion levels

are equal

Acid

increases H+ concentration (HCl)

Base

reduces H+ concentration (NaOH)

Acids are closer to 0? or 14?

0

Bases are closer to 0? or 14?

14

Neutral is

7

pH of water

7 ← neutral

Calculating pH equations (2)

[H+][OH-] = 10-14

pH = -log [H+]

Buffers

minimize changes in concentration of H+ and OH- in a solution (weak acids and bases)

Buffers keep blood at pH?

about 7.4 pH

If blood drops to 7 or up to 7.8 = death :O

Carbonic Acid – Bicarbonate System

important buffers in blood plasma

Here’s a speedy summary: