H2O

Molecular Formula2 atoms of hydrogen,

1 atom oxygen

Try doing a Bohr model for water…

H H

oThe first energy level holds2 electrons, the secondenergy level holds 8electrons, and the third energy level holds 8electrons.

Shell, energy level,valence

Fill up those energy levels!

++

- -

Electrons shared by the atoms spend more time closer to the Oxygen nucleus than the Hydrogen

Results in an unequal electron sharing and a charge separation in the molecule.

The Oxygen has a partial negative charge.

The Hydrogens have a partial positive charge.

The water molecule is NOT an ion; there is NO gain or loss of electrons!

Polar covalent bonds can lead to the formation of a weak bond

called a hydrogen bond.

Polar covalent bonds forms an electrostatic (charge, as in positive attracted to negative) interaction

with a substance of opposite charge.

Water expands (gets less dense) when it freezes.

This is unusual for liquids.

Water floats as a solid.

Water is unique in that it is the only natural substance that is found in

all three states – liquid, solid (ice), and gas (steam) –

at the temperatures normally found on Earth.

Water has a high specific heat index. This means that water can absorb a lot of heat before it begins to get hot.

The high specific heat index of waterhelps regulate the rate at which

air changes temperature, which is why the temperature change

between seasons is gradual than sudden.

Water dissolves more substances than any other liquid.

The boiling point of water gets lower as you go up in altitude.

As altitude gets higher, air pressure (the weight of air above you) becomes less.

With less pressure pushing on a pot of water at a higher altitude, it is easier for the water molecules to break their bonds and attraction to each other and, thus, it boils more easily.

Water has the highest surface tension among common liquids (mercury is higher).

Surface tension is the attraction of molecules to each other on a liquid's surface.

Surface tension is the ability of a substance to stick to itself (cohesion).

Surface tension is a measure of the strength of the water's surface film.

This surface tension permits water to hold up substances heavier and denser than itself.

A steel needle carefully placed on the surface of a glass of water will float.

Plants use capillary action to draw water from the ground up through roots and stems.

Capillary action is important for moving water (and all things

dissolved in it) around.

Capillary action is movement of water within the spaces of a porous material

due to the forces of adhesion, cohesion, and surface tension.

Water is sticky, due to cohesion (water molecules like to stay closely together) and

adhesion (water molecules are attracted and stick to other substances).

Dip a paper towel into a glass of water and the water will "climb" onto the paper towel until the pull of gravity is too much for it to overcome.

Water = nonionic compound. It is converted to ions

in a process called ionization.

Water separates when one of the OH bonds breaks. This results in a positively charged H+ (hydrogen ion)

and a negatively charged OH— hydroxide ion.

ALL LIFE PROCESSES DEPEND ON THIS TINY IONIZATION PROCESS…

The level of H+ and OH— ions in solution

is known as the pH scale

[H+]

pH 1 pH 7 pH 14

[OH—]

What happens to the pH of the solution if the level of [H+] increases?

What happens to the pH of the solution if the level of [OH–] increases?

CO2

What does exhalinginto the water

add to the water?H2O

Bromothymol Blue added

CO2How does this

‘change’ the water?

Why?

CO2 + H2O H2CO3

Carbonic Acid

H2OCO2

Buffer Systems—a buffer is a moleculethat tends to either bind or release hydrogen ions

in order to maintain a particular pH

What happens when the reactions go to the right?

What happens if the reactions go to the left?

Carbonic acid

BicarbonateIon

CarbonateIon

H2CO3

HCO3 --

= carbonic acid (H+ donor) responds to a rise in pH

= bicarbonate (H+ acceptor) responds to a drop in pH

[H+]

pH 1 pH 7 pH 14

Carbonic acid

BicarbonateIon

A diabetic’s blood pH dropped to 7.23. Why?The body enters a starving state due to no insulin output; body burns stored fat for energy and ketones are released into the bloodstreamas a by-product/or waste product of fat metabolism. Ketones are acidic!

What happens during HYPERventilation? Levels of Carbon dioxide decrease; less H+ ions will accumulate causing the pH of blood to increase = alkalosis

What happens during HYPOventilation?Carbon dioxide in blood increases; more H+ ions will accumulate causing the pH of blood to decrease

Maintaining blood pH—why?

Acidosis or Alkalosis = death

What do the lungs do?In general, acids (H+ ions) are stimulating to neurons.

As the carbon dioxide level in the blood increases, it also increases in the cerebrospinal fluid (CSF).

This causes the pH to drop; especially in the brain because there is less buffering ability in CSF than in blood. The low pH (excess H+ ions) stimulates neurons in the medullary respiratory centers to fire more impulses to the diaphragm to increase the rate and depth of breathing.

What do the kidneys do?Regulates HCO3- ions in blood loss of HCO3- ions in blood = decrease blood pH = metabolic acidosis gain of HCO3- ions in blood = increase blood pH = metabolic alkalosis

Parietal Cells of the stomach secrete HCl into the stomachto disrupt the extracellular matrix and kills most bacteria that are swallowed up with food…

HCl converts inactive pepsinogen (whichis secreted by chief cells of the stomach)into active pepsin

Pepsin begins the chemical digestionof proteins by splitting the polypeptidesinto smaller polypeptides…

pH in the Digestive System, producing HCl

Lumen of the

Stomach

Esophagus“peristalsis”

Small Intestine

H2CO3

HCO3

= carbonic acid (H+ donor) responds to a rise in pH

= bicarbonate (H+ acceptor) responds to a drop in pH

[H+]

pH 1 pH 7 pH 14

The Stomach—secretion of HClMovement of molecules by active transport or facilitated diffusion

Cl-

HCO3-

Cl-

H+

HCl

CO2+ H2O

H2CO3

H+HCO3-

CapillaryBloodvessel

Parietal cell

Lumen of stomach

Cl-

+

Bicarbonate ion

Carbonic Acid

H2CO3 HCO3- H++

Buffer system in place to regulate pH

Carbonic Acid Bicarbonate Hydrogen ion