Water

O

HH

Water Basics• Polar: part of a molecule is

slightly positive, while another part is slightly negative

• Oxygen “hogs” electrons from hydrogen– 8 protons: 10 electrons– Negative charge

• Hydrogen– 1 proton: 0 electrons– Positive charge

• Creates hydrogen bonds where one water sticks to another

1

1

1

2

4

3

2

1

6

5

1

1

+ +

-

Red = Oxygen (negative) White = Hydrogen (positive)

+ + + +

+

+ +

+ + +

+ +

+ +

+

+++

+ +

+ +

+

+ +

+

+

++

+ +++

+

+ +

++

+ + +

+ +

+ +

+ +

+++++++

- - -

- -

----

-

- -

-

- - - - -

----

- - - -

Water Properties• High specific heat:

Resists temp changes– Much energy needed

to break water bonds– Helps to maintain a

constant body temp• Cohesion: polar water

molecules attracted to other polar water molecules

• Adhesion: polar water sticks to other moleculesWhy can this insect walk on water?

It is not heavy enough to break the bonds that hold the water molecules together.

7ml

6.8ml

Solutions• Solution: mixture where 1

substance dissolves in another

• 2 parts to a solution1) Solute: substance that

dissolves• Atoms, ions, molecules

2) Solvent: substance in which the solute is dissolved• Usually waterSUGAR

KOOL AID

Solution

Solutions• Solution: mixture where 1

substance dissolves in another

• 2 parts to a solution1) Solute: substance that

dissolves• Atoms, ions, molecules

2) Solvent: substance in which the solute is dissolved• Usually water

Ex: Human blood– Solvent: Plasma (watery

part of blood) – Solutes: Carbs, proteins,

sugars, etc…

• pH scale measures the amount of H+ ions in a solution• 1 minute: Discuss with your neighbor:

A) Which base has the most H+ ions?B) Which substance has the fewest H+ ions?C) Which is the strongest acid?

pH ScaleAcid Base

neutralMore OH-

More H+ Few H+Few OH-

LemonsMilk

AmmoniaSoft drink

BloodBaking soda

blood

Ammonia

Lemons

• pH scale measures the amount of H+ ions

• Some molecules release H+ ions when dissolved

• H+ ions accumulate (acids)

pH Scale

H+

H+H+H+H+H+

H+H+ H+

Substance A

Acidic Solution

• pH scale measures the amount of H+ (hydrogen) ions

• Some molecules release H+ ions when dissolved

• H+ ions accumulate (acids)

• Some molecules release OH- (hydroxide) ions when dissolved

• OH- ions accumulate (bases)

pH Scale

OH-

OH-OH-OH-

OH-

OH-

OH- OH- OH-Substance B

Basic (alkaline) Solution

• pH scale measures the amount of H+ ions• Some molecules release H+ ions when dissolved

• H+ ions accumulate (acids)• Some molecules release OH- ions when dissolved

• OH- ions accumulate (bases)• pH balance vital to life

– Ex: Blood pH (7.4): Proteins break down outside normal pH

pH Scale

• Normally: Balance of H+ and OH- ions in blood (7.4 pH)

• Alcohol abuse: Excess alcohol lowers blood pH (H+ ions accumulate)

• Kidney removes excess H+• Can lead to kidney damage

Blood pH

H+

OH-

OH-

OH-

OH-

OH-

OH-

OH-

OH-

OH-

OH-

OH-

H+

H+H+

H+

H+H+H+

H+ H+

H+

H+

H+

H+

H+

H+

H+H+

H+

H+

Review1) Vocabulary: Polar, Adhesion, Cohesion, High Specific Heat, Solution,

Solute, Solvent, pH 2) Name 4 basic features of water.3) Which water property explains that one atom is positively charged,

while another is negatively charged?4) How does cohension and adhesion differ?5) Which is a stronger acid? Substance A with a pH of 5 or substance B

with a pH of 3?6) Which has more H+ ions? Substance A with a pH of 5 or substance B

with a pH of 3?7) Which has more OH- ions? Substance A with a pH of 5 or substance B

with a pH of 3?8) How does a solute differ from a solvent?9) What is the solute and solvent of blood?