Water

1
Water

• Chapter 3

2
Water

• Life began in water
• 2/3s of an organisms body
• Organisms grow or reproduce in a water-rich
  environment. 

3
Water Molecule

• Covalent bonding
• Oxygen is more electronegative
• Polar molecule
• Polarity of water underlies its chemistry
• Chemistry of life.

4
Polar molecule
5
Polar molecule
6
Hydrogen bonding
7
Fig. 3-2
?
Hydrogen bond
?
H

O
?

?
H
?
?
?
?
8
Properties of water

• Cohesion
• Attraction between water molecules
• Responsible for surface tension of water

9
Properties of water

• Adhesion
• Attraction of water between other molecules
• Capillary action

10
Properties of water

• Moderation of water temperature
• Water is a liquid at moderate temperatures
• Specific heat
• Amount of heat needed to a raise 1 gram of a
  substance 10 Celsius
• Waters specific heat is 1
  calorie/gram/0C (4.18Joules)

11
Properties of water

• Evaporative cooling
• Heat of vaporization
• Amount of heat needed to change 1 gram of a
  substance from a liquid to a gas.
• 586 Calories (2260 Joules)

12
Properties of water

• Ice floats
• Less dense

13
Fig. 3-6a
Hydrogen bond
Liquid water Hydrogen bonds break and re-form
Ice Hydrogen bonds are stable
14
Properties of water

• Solvent
• Water surrounds ionic polar molecules
• Table salt or sugar
• Aqueous solution
• Molarity

15
Fig. 3-7

Na








Na




Cl
Cl








16
Hydrophobic

• fear of water
• Common in non-polar molecules
• Non-polar molecules tend to aggregate in water
• Hydrophobic exclusion

17
Hydrophilic

• water-loving
• Common in polar molecules

18
Ionization
Fig. 3-UN2
H
H

• Process of spontaneous ion formation
• H2O H OH-
• Dissociation

H
O
O
O
O
H
H
H
H
H
2H2O
Hydroxide ion (OH)
Hydronium ion (H3O)
19
pH

• Measurement of the concentration of hydrogen ion.
• pH -logH
• Acid
• Increase concentration of H ions or a lower pH.
• Base
• Decrease in concentration of Hions or a higher
  pH.

20
Fig. 3-UN5
0
Acidic H gt OH
Acids donate H in aqueous solutions
Neutral H OH
7
Bases donate OH or accept H in aqueous solutions
Basic H lt OH
14
21
pH
22
Fig. 3-9
pH Scale
0
1
Battery acid
Gastric juice, lemon juice
2
H
H
H
Vinegar, beer, wine, cola
OH
H
3
H
OH
Increasingly Acidic H gt OH
H
H
H
4
Tomato juice
Acidic solution
Black coffee
5
Rainwater
6
Urine
OH
Saliva
OH
Neutral H OH
7
Pure water
OH
H
H
OH
OH
Human blood, tears
H
H
H
8
Seawater
Neutral solution
9
10
Increasingly Basic H lt OH
Milk of magnesia
OH
OH
11
OH
OH
H
Household ammonia
OH
OH
OH
H
12
Basic solution
Household bleach
13
Oven cleaner
14
23
Buffer

• Substance helps maintain a balanced pH
• Accepts H ions when excess
• Donates when there are too few.

24
Buffer

• Blood pH is approximately 7.4.
• Bicarbonate ion helps maintain the pH of the
  blood.
• Blood acidosis pH drops 0.2 to 0.4 points on the
  pH scale
• Blood alkalosis pH goes up 0.2 to 0.4 points on
  the pH scale

25
Buffer

• Bicarbonate ion
• H2CO3 ? HCO3- H

26
Acid rain

• Sulfuric acid
• Nitric acid

27
Acid rain